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On Various Aspects of Decomposition of Austenite in a High-Silicon Steel During Quenching and Partitioning
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Mahesh Chandra Somani , D. A. Porter , L. P. Karjalainen , R. D. K. Misra
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2013
Metallurgical and Materials Transactions A
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Using a Gleeble thermomechanical simulator, a high-silicon steel (Fe-0.2C-1.5Si-2.0Mn-0.6Cr) was laboratory hot-rolled, re-austenitized, quenched into the M s–M f range, retaining 15 to 40 pct austenite at the quench stop temperature (T Q), and annealed for 10 to 1000 seconds at or above T Q in order to better understand the mechanisms operating during partitioning. Dilatometer measurements, transmission electron microscopy, and calculations showed that besides carbon partitioning, isothermal martensite and bainite form at the partitioning temperature. While isothermal martensite formation starts almost immediately after quenching with the rate of volume expansion dropping all the time, the beginning of bainite formation is marked by a sudden increase in the rate of expansion. The extent of its formation depends on the partitioning temperature following TTT diagram predictions. At the highest partitioning temperatures martensite tempering competes with partitioning. Small fractions of bainite and high-carbon martensite formed on cooling from the partitioning temperature. The average carbon content of the austenite retained at room temperature as determined from XRD measurements was close to the carbon content estimated from the M s temperature of the martensite formed during the final cooling.
DOI : 10.1007/s11661-013-2053-8
Anahtar Kelimeler : Austenite, Martensite, Bainite, Martensite Lath, Lower Bainite
ISSN: 1543-1940
Cilt: 45
Sayı: 3
Sayfa: 1247-1257
Sınıflandırma :
2
The dislocation substructure, carbides and the deformation mechanism map for AISI 304 stainless steel
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Ravindra K. Bhargava , John Moteff , Robert W. Swindeman
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
DOI : 10.1007/BF02644086
Anahtar Kelimeler : Crack Opening Displacement, Dislocation Substructure, Precipitate Temperature Time, Typical Dislocation Substructure
ISSN: 1543-1940
Cilt: 7
Sayı: 5
Sayfa: 879-884
Sınıflandırma :
3
Theory of workhardening 1934-1984
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Doris Kuhlmann-Wilsdorf
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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The evolution of the theory of workhardening through the past fifty years has laid a secure basis, but much research still lies ahead. A guiding principle in the prevailing, so-called meshlength theory is that glide dislocations arrange into stress-screened, low-energy structures, the most common being the cell structure, and that the flow stress is the stress needed to generate new glide dislocations. Further, it makes extensive use of the “principle of similitude”. Remnant stresses due to dislocations with just one Burgers vector orientation are very often relieved by additional dislocations with other Burgers vectors which form not in response to the applied stress but to those remnant stresses. Such dislocations are commonly misnamed “forest” dislocations. The theory closely reproduces stages II and III of the typical workhardening curve. Stage I results in single glide from sources which initially are isolated from each other so that pile-ups form, which then may interact among neighboring pile-ups of opposite sign, so as to generate mats of dipoles parallel to the active glide plane. Stage II behavior is expected as long as similitude is obeyed so that the average free dislocation path shrinks inversely proportional with the root of the dislocation density. Stage III, finally, results when the free dislocation path is constant. At low temperatures, thermal activation can make the critical difference for the release of hair-trigger poised loops. This is the cause of creep effects whose magnitude is limited to less than the elastic strain. Computer calculations indicate the presence of longer-range (i.e., cell diameter scale) stresses whose sign changes with the cell’s sense of rotation. This suggests that rectangled dislocation cells with a common rotation axis, arranged into a three-dimensional checkerboard pattern in which the sense of rotation alternates from cell to cell, should minimize stored energy. Such cell patterns are increasingly reported in the literature. The fact that the average cell diameter tends to be inversely proportional to the applied stress is also readily explained through those stresses. In retrospect, Taylor’s theory of workhardening may be recognized as a variant of the meshlength theory of stage III, in that it is based on a stress-screened network obeying the principle of similitude while the free dislocation path, given by the spacing between the mosaic block walls, remains constant.
DOI : 10.1007/BF02670414
Anahtar Kelimeler : Metallurgical Transaction, Workhardening, Flow Stress, Applied Stress, Burger Vector
ISSN: 1543-1940
Cilt: 16
Sayı: 12
Sayfa: 2091-2108
Sınıflandırma :
4
Compression along the Easy-Glide Orientation of Ultrafine and Fine-Grained Mg-3Al-1Zn Alloy
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
W. T. Lee , Y. W. Chou , C. I. Hsiao , C. P. Chang , L. Chang , P. W. Kao
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2010
Metallurgical and Materials Transactions A
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The deformation behavior of textured ultrafine-grained (UFG) and fine-grained (FG) Mg-3Al-1Zn alloy compressed along the easy-glide orientation was studied. It was found that severe strain localization within very thin shear bands (SBs) caused the loss of ductility in UFG Mg-3Al-1Zn alloy. Increasing grain size increases the width of SBs, which decreases the degree of strain localization. The reason for the occurrence of severe strain localization in textured UFG Mg-3Al-1Zn alloy is proposed.
DOI : 10.1007/s11661-010-0464-3
Anahtar Kelimeler : Shear Band, Slip System, Pole Figure, Equal Channel Angular Pressing, Orientation Distribution Function
ISSN: 1543-1940
Cilt: 41
Sayı: 13
Sayfa: 3282-3286
Sınıflandırma :
5
Microstructure and Mechanical Behavior of Powder Metallurgy Mg 98.5 Gd 1 Zn 0.5 Alloy
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Sandra Cabeza , Gerardo Garcés , Pablo Pérez , Paloma Adeva
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2013
Metallurgical and Materials Transactions A
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The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.
DOI : 10.1007/s11661-013-2041-z
Anahtar Kelimeler : Magnesium Alloy, Ultimate Tensile Strength, Powder Metallurgy, High Strain Rate, Threshold Stress
ISSN: 1543-1940
Cilt: 45
Sayı: 8
Sayfa: 3222-3231
Sınıflandırma :
6
Hydrogen attack behavior of the heat affected zone of a 2.25Cr-1Mo steel weldment
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
T. A. Parthasarathy , P. G. Shewmon
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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The kinetics of hydrogen attack (HA) has been studied in the heat affected zone (HAZ) in a 2.25Cr-1Mo steel weld to determine the relative rates of attack and bubble nucleation in the HAZ, base metal, and weld metal. The HAZ was found to suffer hydrogen attack at nearly twice the rate of the base metal, but not as rapidly as the weld metal. Nucleation of bubbles does not occur during HA of the HAZ of a 2.25Cr-1Mo steel, on exposure to hydrogen pressure of 20.5 MPa or less, but does occur at higher pressures up to 31.5 MPa (4500 psi) at 550 °C, or up to 27.5 MPa (4000 psi) at 580 °C. Such nucleation results in enhancement of the HA rate by a factor of six. The weak dependence of nucleation effects on hydrogen pressure and the saturation of the nucleation effects in a short time suggest some thermally activated nucleation of fresh bubbles.
DOI : 10.1007/BF02647200
Anahtar Kelimeler : Metallurgical Transaction, Base Metal, Weld Metal, Heat Affected Zone, Hydrogen Pressure
ISSN: 1543-1940
Cilt: 18
Sayı: 7
Sayfa: 1309-1312
Sınıflandırma :
7
Through-thickness texture gradient in an annealed Al-Mg Alloy sheet
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Jiantao Liu , S. W. Banovic , F. S. Biancaniello , R. D. Jiggetts
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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DOI : 10.1007/s11661-005-1016-0
Anahtar Kelimeler : Material Transaction, Cold Rolling, Continuous Cast, Texture Component, Deformation Texture
ISSN: 1543-1940
Cilt: 36
Sayı: 13
Sayfa: 869-874
Sınıflandırma :
8
The effect of composition and milling conditions on the structure of mechanically alloyed Mg-Al based alloys
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Lowell E. Hazelton
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Mg-Al based alloys were mechanically alloyed under varying conditions. Elemental reaction times correlated with known diffusion coefficients and elemental hardness, but milling temperature had almost no effect over a 200 °C range. Increasing impact energy caused the steady-state level of crystallinity to increase. Alloys with up to 6 at. pct of Ti, Y, Ca, Zr, V, Er, or Pr yielded amorphous alloys near the composition Mg40Al60. Certain phases were suppressed by mechanical alloying, while others became more dominant than in the equilibrium phase diagram. These effects are explained by differential scanning calorimetry (DSC) results, which indicate they are growth rate controlled during mechanical alloying. Hard elements such as Cr and Mo with positive free energy of mixing did not react completely even after relatively long milling times.
DOI : 10.1007/s11661-001-0184-9
Anahtar Kelimeler : Differential Scanning Calorimetry, Milling, Material Transaction, Amorphous Phase, Mechanical Alloy
ISSN: 1543-1940
Cilt: 32
Sayı: 12
Sayfa: 3099-3108
Sınıflandırma :
9
Size Effect of Rare-Earth Intermetallics in Sn-9Zn-0.5Ce and Sn-3Ag-0.5Cu-0.5Ce Solders on the Growth of Tin Whiskers
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
T.H. Chuang , H.J. Lin
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2008
Metallurgical and Materials Transactions A
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Kaydet
In contrast to the large cluster-shaped CeSn3 peritectic phase formed in Sn-3Ag-0.5Cu-0.5Ce solder, Sn-9Zn-0.5Ce possesses very fine (Ce0.8Zn0.2)Sn3 intermetallics. Image analyses indicate that the total exposed area of fine peritectic intermetallics in Sn-9Zn-0.5Ce solder is near that of coarse clusters in Sn-3Ag-0.5Cu-0.5Ce. However, long fiber-type and coarse hillock-type whiskers have been observed on the surface of Sn-3Ag-0.5Cu-0.5Ce after air storage at room temperature and 150 °C, respectively. On the contrary, only tin sprouts appear on the oxide layer of peritectic (Ce0.8Zn0.2)Sn3 intermetallics of Sn-9Zn-0.5Ce solder. The prevention of the lengthening and coarsening of these tin sprouts in Sn-9Zn-0.5Ce solder is attributed to the small size of its rare-earth (RE) containing peritectic clusters. The results imply that Zn atoms have an inhibition effect for the whisker growth of RE-doped solders.
DOI : 10.1007/s11661-008-9632-0
Anahtar Kelimeler : Solder Joint, Whisker Growth, Weight Gain Percentage, Ball Grid Array Package, Thermal Gravity Analyzer
ISSN: 1543-1940
Cilt: 39
Sayı: 12
Sayfa: 2862-2866
Sınıflandırma :
10
Microstructure of Precipitation Hardenable Powder Metallurgical Ni Alloys Containing 35 to 45 pct Cr and 3.5 to 6 pct Nb
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Uffe D. Bihlet , Kristian V. Dahl , Marcel A. J. Somers
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2014
Metallurgical and Materials Transactions A
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Kaydet
Ni-based alloys with high Cr contents are not only known for their excellent high temperature and hot corrosion resistance, but are also known for poor mechanical properties and difficult workability. Powder metallurgical (PM) manufacturing of alloys may overcome several of the shortcomings encountered in materials manufacturing involving solidification. In the present work, six PM Ni-based alloys containing 35 to 45 wt pct Cr and 3.5 to 6 wt pct Nb were produced and compacted via hot isostatic pressing. Samples were heat treated for up to 1656 hours at either 923 K or 973 K (650 °C or 700 °C), and the microstructures and mechanical properties were quantified and compared to thermodynamic calculations. For the majority of the investigated alloys, the high Cr and Nb contents caused development of primary populations of globular α-Cr and δ (Ni3Nb). Transmission electron microscopy of selected alloys confirmed the additional presence of metastable γ″ (Ni3Nb). A co-dependent growth morphology was found, where the preferred growth direction of γ″, the {001} planes of γ-Ni, caused precipitates of both α-Cr and δ to appear in the form of mutually perpendicular oriented disks or plates. Solution heat treatment at 1373 K (1100 °C) followed by aging at 973 K (700 °C) produced a significant strength increase for all alloys, and an aged yield strength of 990 MPa combined with an elongation of 21 pct is documented for Ni 40 wt pct Cr 3.5 wt pct Nb.
DOI : 10.1007/s11661-014-2469-9
Anahtar Kelimeler : Solution Heat Treatment, Ni3Nb, Powder Metallurgical, Prolonged Aging Time, Quantitative Microstructure Analysis
ISSN: 1543-1940
Cilt: 45
Sayı: 11
Sayfa: 4796-4809
Sınıflandırma :
11
Grain boundary segregation and grain growth inhibition in silicon iron: The effect of boron and nitrogen
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
R. Grant Rowe
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
The degree of grain growth inhibition in iron-3.1 pct silicon alloys with small additions of boron, nitrogen and sulfur has been observed to correlate strongly with the degree of nitrogen segregation to the grain boundaries. Grain growth was seen to increase monotonically with decreasing nitrogen segregation at 950°C, the temperature at which significant grain growth was first observed to occur. Boron affected the retention of nitrogen in the material at high temperatures and in this way had an indirect effect on grain growth inhibition. Sulfur acted to enhance the effectiveness of nitrogen as a grain growth inhibitor. It is suggested that nitrogen, even at very low grain boundary concentrations affects grain boundary migration by poisoning sites at the grain boundaries which are particularly efficient in attaching atoms to the growing grain surface.
DOI : 10.1007/BF02811646
Anahtar Kelimeler : Boron, Metallurgical Transaction, Auger, Phase Particle, Boundary Migration
ISSN: 1543-1940
Cilt: 10
Sayı: 8
Sayfa: 997-1011
Sınıflandırma :
12
Delamination Fracture Related to Tempering in a High-Strength Low-Alloy Steel
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Wei Yan , Wei Sha , Lin Zhu , Wei Wang , Yi-Yin Shan , Ke Yang
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2009
Metallurgical and Materials Transactions A
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The delamination or splitting of mechanical test specimens of rolled steel plate is a phenomenon that has been studied for many years. In the present study, splitting during fracture of tensile and Charpy V-notch (CVN) test specimens is examined in a high-strength low-alloy plate steel. It is shown that delamination did not occur in test specimens from plate in the as-rolled condition, but was severe in material tempered in the temperature range 500 °C to 650 °C. Minor splitting was seen after heating to 200 °C, 400 °C, and 700 °C. Samples that had been triple quenched and tempered to produce a fine equiaxed grain size also did not exhibit splitting. Microstructural and preferred orientation studies are presented and are discussed as they relate to the splitting phenomenon. It is concluded that the elongated as-rolled grains and grain boundary embrittlement resulting from precipitates (carbides and nitrides) formed during reheating were responsible for the delamination.
DOI : 10.1007/s11661-009-0068-y
Anahtar Kelimeler : Fracture Surface, HSLA Steel, Impact Toughness, Lower Bainite, Charpy Impact Test
ISSN: 1543-1940
Cilt: 41
Sayı: 1
Sayfa: 159-171
Sınıflandırma :
13
Optimization of the strength-fracture toughness relation in particulate-reinforced aluminum composites via control of the matrix microstructure
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
I. Dutta , T. R. McNelley , R. Nagarajan , F. N. Quiles
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulate-reinforced aluminum alloy 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the strength-toughness combination in the composite can be optimized over a wide range of properties, without resorting to unstable, underaged (UA) matrix microstructures, which are usually deemed necessary to produce a higher fracture toughness than that displayed in the peak-aged condition. Further, it is demonstrated that, following an appropriate combination of thermomechanical processing and unconventional heat treatment, the composite may possess better stiffness, strength, and fracture toughness than a similar unreinforced alloy. In the high- and low-strength matrix microstructural conditions, the matrix grain and substructure were found to play a substantial role in determining fracture properties. However, in the intermediate-strength regime, properties appeared to be optimizable by the utilization of heat treatments only. These observations are rationalized on the basis of current understanding of the grain size dependence of fracture toughness and the detailed microstructural features resulting from thermomechanical treatments.
DOI : 10.1007/s11661-998-0119-9
Anahtar Kelimeler : Fracture Toughness, Material Transaction, Transmission Electron Micro, Solution Anneal, Matrix Microstructure
ISSN: 1543-1940
Cilt: 29
Sayı: 9
Sayfa: 2433-2446
Sınıflandırma :
14
Pressure-assisted reactive synthesis of titanium aluminides from dense 50Al-50Ti elemental powder blends
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
E. Paransky , E. Y. Gutmanas , I. Gotman , M. Koczak
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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In the present research, dense γ-TiAl based intermetallic samples were fabricated by reactive synthesis of fully dense elemental 50 at. pct Al-50 at. pct Ti powder blends. Two different processing routes were attempted: thermal explosion under pressure (combustion consolidation) and reactive hot pressing. In both approaches, relatively low processing or preheating temperatures (900 °C) were used. The entire procedure of thermal explosion under pressure could be performed in open air without noticeable oxidation damage to the final product. The application of a moderate external pressure (≤250 MPa) during synthesis was shown to be enough to accommodate the negative volume change associated with TiAl formation from the elemental components and, thereby, to ensure full density of the final product. Microstructure and phase composition of the materials obtained were characterized employing X-ray diffraction and scanning electron microscopy with energy dispersive analysis. It was found that at elevated temperatures(e.g., 900 °C), the equiatomic 50Al-50Ti alloy lies beyond the homogeneity range of the y-TiAl phase in the Ti-Al binary and contains, in addition to γ-TiAl, Al-rich Ti3Al. Mechanical properties of the materials synthesized were evaluated in compression tests at different temperatures and by microhardness measurements. Due to its very fine microstructure, the Ti-Al material synthesizedvia reactive hot pressing exhibited superplastic behavior at temperatures as low as 800 °C.
DOI : 10.1007/BF02651868
Anahtar Kelimeler : Material Transaction, Thermal Explosion, Scanning Electron Micro, Full Density, Powder Blend
ISSN: 1543-1940
Cilt: 27
Sayı: 8
Sayfa: 2130-2139
Sınıflandırma :
15
Embrittlement of Intercritically Reheated Coarse Grain Heat-Affected Zone of ASTM4130 Steel
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Liying Li , Tao Han , Bin Han
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2018
Metallurgical and Materials Transactions A
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Kaydet
In this investigation, a thermal welding simulation technique was used to investigate the microstructures and mechanical properties of the intercritically reheated coarse grain heat-affected zone (IR CGHAZ) of ASTM4130 steel. The effect of post weld heat treatment (PWHT) on the toughness of IR CGHAZ was also analyzed. The toughness of IR CGHAZ was measured by means of Charpy impact, and it is found that IR CGHAZ has the lowest toughness which is much lower than that of the base metal regardless of whether PWHT is applied or not. The as-welded IR CGHAZ is mainly composed of ferrite, martensite, and many blocky M–A constituents distributing along grain boundaries and subgrain boundaries in a near-connected network. Also, the prior austenite grains are still as coarse as those in the coarse grain heat-affected zone (CGHAZ). The presence of the blocky M–A constituents and the coarsened austenite grains result in the toughness deterioration of the as-welded IR CGHAZ. Most of the blocky M–A constituents are decomposed to granular bainite due to the effect of the PWHT. However, PWHT cannot refine the prior austenite grains. Thus, the low toughness of IR CGHAZ after PWHT can be attributed to two factors, i.e., the coarsened austenite grains, and the presence of the remaining M–A constituents and granular bainite, which are located at grain boundaries and subgrain boundaries in a near-connected network. The absorbed energy of the IR CGHAZ was increased by about 3.75 times, which means that the PWHT can effectively improve the toughness but it cannot be recovered to the level of base metal.
DOI : 10.1007/s11661-018-4480-z
ISSN: 1543-1940
Cilt: 49
Sayı: 4
Sayfa: 1254-1263
Sınıflandırma :
16
Sixty Years of Casting Research
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
John Campbell
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2015
Metallurgical and Materials Transactions A
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The 60 years of solidification research since the publication of Chalmer’s constitutional undercooling in 1953 has been a dramatic advance of understanding which has and continues to be an inspiration. In contrast, 60 years of casting research has seen mixed fortunes. One of its success stories relates to improvements in inoculation of gray irons, and another to the discovery of spheroidal graphite iron, although both of these can be classified as metallurgical rather than casting advances. It is suggested that true casting advances have dated from the author’s lab in 1992 when a critical surface turbulence condition was defined for the first time. These last 20 years have seen the surface entrainment issues of castings developed to a sufficient sophistication to revolutionize the performance of light alloy and steel foundries. However, there is still a long way to go, with large sections of the steel and Ni-base casting industries still in denial that casting defects are important or even exist. The result has been that special ingots are still cast poorly, and shaped casting operations have suffered massive losses. For secondary melted and cast materials, electro-slag remelting has the potential to be much superior to expensive vacuum arc remelting, which has cost our aerospace and defense industries dearly over the years. This failure to address and upgrade our processing of liquid metals is a serious concern, since the principle entrainment defect, the bifilm, is seen as the principle initiator of cracks in metals; in general, bifilms are the Griffith cracks that initiate failures by cracking. A new generation of crack resistant metals and engineering structures can now be envisaged.
DOI : 10.1007/s11661-015-2955-8
Anahtar Kelimeler : Ductile Iron, Austempering, Gravity Casting, Compact Graphite Iron, Oxide Bifilms
ISSN: 1543-1940
Cilt: 46
Sayı: 11
Sayfa: 4848-4853
Sınıflandırma :
17
Diffusion controlled stress rupture of polycrystalline materials
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
R. J. Charles
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
The high temperature stress rupture process in polycrystalline solids is examined in terms of grain boundary parting by vacancy condensation at the tip of a crack within the boundary. The gradient for diffusion of these defects is considered in the model to arise from the stress gradient in advance of the flaw tip. A rupture stress function is derived which is shown to closely describe the stress rupture behavior of a number of metals and high temperature alloys.
DOI : 10.1007/BF02656590
Anahtar Kelimeler : Metallurgical Transaction, Stress Intensity Factor, Rupture Data, Polycrystalline Solid, Stress Rupture Data
ISSN: 1543-1940
Cilt: 7
Sayı: 8
Sayfa: 1081-1089
Sınıflandırma :
18
Thermodynamic description of the Cu-Al-Sn system in the copper-rich corner
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Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
J. Miettinen
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Thermodynamic optimization of the Cu-Al-Sn system is made using classical thermodynamic models for describing the properties of the individual phases of the system. The optimization is limited to the copper-rich corner of the system, the gamma phase of the Cu-Al and Cu-Sn systems being the remotest phase included in the analysis. The data of the pure components and the binary systems are taken from the previously assessed Scientific Group Thermodata Europe (SGTE)-compatible descriptions, although a slight reoptimization of data is first made for the bcc, fcc, and gamma phases of the Cu-Al system and for the liquid and gamma phases of the Cu-Sn system. Next, ternary thermodynamic data are optimized for the ternary Cu-Al-Sn system using the experimental phase-equilibrium data of the literature. The results of the optimization are presented by comparing the original, experimental data with the calculations, and reasonable agreement is demonstrated.
DOI : 10.1007/s11661-002-0173-7
Anahtar Kelimeler : Material Transaction, Thermodynamic Description, Experimental Data Point, Gamma Phase, Sublattice Model
ISSN: 1543-1940
Cilt: 33
Sayı: 6
Sayfa: 1639-1648
Sınıflandırma :
Fizik %22
19
Rationalization of Short-Term Creep Test Data and Prediction of Long-Term Creep Strengths of a Fe-20Cr-25Ni (Wt Pct) Austenitic Stainless Steel (Alloy 709)
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
P. C. Yi , C. C. Jiang , Z. Dong , X. L. Song , J. Jia , Z. D. Xiang
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2019
Metallurgical and Materials Transactions A
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Kaydet
A new creep model is applied to rationalize the stress and temperature dependences of minimum creep rate for a Fe-20Cr-25Ni (wt pct) austenitic stainless steel (Alloy 709). The creep activation energy determined on the basis of this model does not depend on stress and the stress exponent not on temperature. Consequently, it can be used together with the Mankman–Grant relationship to predict the long-term creep strengths and lifetimes at different temperatures using short-term creep rupture data.
DOI : 10.1007/s11661-019-05292-z
ISSN: 1543-1940
Cilt: 50
Sayı: 8
Sayfa: 3452-3457
Sınıflandırma :
20
Modeling of dissolution, growth, and coarsening of aluminum nitride in low-carbon steels
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Leon M. Cheng , E. Bruce Hawbolt , T. Ray Meadowcroft
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
A the oretically based model was developed by using numerical integration methods on a multiparticle system to predict the dissolution and growth kinetics of nitrides and carbides in steels undergoing heat treatment. This model takes fully into account the equilibrium thermodynamic properties of the systems, the local equilibrium at the interface, curvature effects, and diffusion along the grain boundary. Dissolution and coarsening are being treated as one continuous, simultaneous process. In the present work, the model is applied to study the dissolution and coarsening behavior of aluminum nitride (A1N) in Al-killed low-carbon steels. The oretically predicted particle-size distributions are in good agreement with the experimental measurements.
DOI : 10.1007/s11661-000-0218-8
Anahtar Kelimeler : Ferrite, Austenite, Material Transaction, Aluminum Nitride, Diffusion Field
ISSN: 1543-1940
Cilt: 31
Sayı: 8
Sayfa: 1907-1916
Sınıflandırma :
21
Effect of nodularity on resonant vibration fracture behavior in upper bainitic and ferritic cast irons
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
S. C. Lin , T. S. Lui , L. H. Chen
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
This work examines resonant vibration fatigue fracture behavior. According to those results, the region I section of the D-N curve (deflection amplitude vs number of vibration cycles) declined with decreasing graphite nodularity or a changing of the matrix to a bainitic structure. Resonant vibration fatigue cracks were often initiated at graphite particles on the surface and grew into the body of the specimen. Initiation and propagation of these cracks were promoted by lowering the graphite nodularity, but no significant difference in deflection amplitude was observed with a bainitic or ferritic matrix microstructure. Bainitic cast iron speciments proved to have a higher initial deflection amplitude and would simply drop almost without displaying region I as the cycle numbers of vibration increased.
DOI : 10.1007/s11661-000-0137-8
Anahtar Kelimeler : Material Transaction, Cast Iron, Spheroidal Graphite, Major Crack, Resonant Vibration
ISSN: 1543-1940
Cilt: 31
Sayı: 9
Sayfa: 2193-2203
Sınıflandırma :
22
Effect of Au Addition on the Microstructure and Properties of Ag-4Pd Bonding Wires
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Bing-Hau Kuo , Du-Cheng Tsai , Yen-Lin Huang , Po-Chun Hsu , Tung-Han Chuang , Hsing-Hua Tsai , Fuh-Sheng Shieu
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2018
Metallurgical and Materials Transactions A
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Kaydet
Silver-based bonding wires such as Ag-4Pd and Ag-8Au-3Pd have drawn remarkable attention in the packaging industry because they are cheaper and more conductive than Au- and Cu-based wires, respectively. This study aimed to investigate the intermetallic compound (IMC) formation and growth at the bonding interface between Ag-4Pd wire and Al-pads and between Ag-8Au-3Pd wire and Al-pads. The as-bonded and reliability-tested Ag-4Pd/Al and Ag-8Au-3Pd/Al specimens were then investigated by transmission electron microscopy (TEM) and scanning transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (STEM-EDS). The bonding properties were examined by ball shear and wire pull tests. In the as-bonded state, hexagonal close-packed (HCP) (Ag, Pd)2Al and HCP Ag2Al were formed at the Ag-4Pd/Al interfaces, whereas dual phase consisting of face-centered cubic Ag alloy with HCP precipitates (Ag, Au, Pd)2Al crystals and HCP Ag2Al layers were observed at the Ag-8Au-3Pd/Al interfaces. The IMCs showed significant growth and oxidation during reliability tests at 130 °C and 85 pct relative humidity for 192 hours. Alloying Au in Ag-4Pd wires promoted the growth of the IMC layer and it also enhanced the mechanical properties in the as-bonded material. By contrast, overgrowth of the IMCs in the Ag-8Au-3Pd/Al system induced microcrack formation in bonding and thus degraded the reliability of the material.
DOI : 10.1007/s11661-018-4841-7
ISSN: 1543-1940
Cilt: 49
Sayı: 11
Sayfa: 5411-5422
Sınıflandırma :
23
Separate Evaluation of the Kinetics of Carbide Precipitation Occurring at the Interface of Preexisting Particles and Within the Austenitic Matrix in a Microalloyed Steel
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Jae-Gil Jung , Eunjoo Shin , Young-Kook Lee
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2016
Metallurgical and Materials Transactions A
Yayıncı Web Sitesi Tam Metin
Kaydet
The isothermal kinetics of carbide precipitation occurring at the interface of preexisting (Ti,Nb)(N,C) particles and within the deformed γ-austenite matrix were separately evaluated using a Nb-Ti-V microalloyed steel through small-angle neutron scattering and transmission electron microscopy. While the specimen was isothermally held after deformation at 1223 K (950 °C), (Nb,Ti)(C,N) particles were precipitated at the interface of coarse (Ti,Nb)(N,C) particles preexisting in the recrystallized γ matrix. This resulted in a single size distribution curve, which was converted from the measured magnetic scattering cross section. However, during isothermal holding after deformation at 1123 K (850 °C), fine (Nb,Ti,V)(C,N) particles formed mainly within the deformed γ matrix, although some of them were precipitated at the interface of preexisting coarse (Ti,Nb)(N,C) particles. Accordingly, the specimens held at 1123 K (850 °C) exhibited double size distribution curves. The separate evaluation between matrix and interface precipitation kinetics was successfully performed using the size distribution curves due to the difference in particle size according to the nucleation site. The reliability of carbide precipitation kinetics was confirmed by comparing the measured ratio between magnetic and nuclear scattering cross sections with the ratio calculated based on the measured chemical composition of precipitates.
DOI : 10.1007/s11661-016-3841-8
Anahtar Kelimeler : Isothermal Holding, Carbide Precipitation, Scattering Cross Section, Matrix Precipitation, Interface Precipitation
ISSN: 1543-1940
Cilt: 48
Sayı: 1
Sayfa: 76-85
Sınıflandırma :
24
Prediction of Glass-Forming Compositions in Metallic Systems: Copper-Based Bulk Metallic Glasses in the Cu-Mg-Ca System
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Kevin J. Laws , Karl F. Shamlaye , Kenneth Wong , Bulent Gun , Michael Ferry
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2010
Metallurgical and Materials Transactions A
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Kaydet
A novel methodology for predicting specific compositions for glass-forming alloys based on efficiently packed atomic cluster selection, liquidus lines, and ab initio calculations is presented. This model has shown applicable adaptation to many known metallic and ceramic oxide glass-forming systems and has led to the discovery of soon to be reported Ag- and Zn-based bulk metallic glasses (BMGs). As a model system, glass formation in the Cu-Mg-Ca ternary system has been assessed using this alloy design methodology, which has led to the discovery of a number of Cu-based BMGs with compositions ranging from Cu-33 to 55 at. pct, Mg-18 to 45 at. pct, and Ca-18 to 36 at. pct. Included in this work are the calculated values of associated cluster binding energies and correlations between physical and thermal properties of these glassy compositions, which show significant physical evidence to support the likely existence of such clusters.
DOI : 10.1007/s11661-010-0274-7
Anahtar Kelimeler : Metallic Glass, Amorphous Alloy, Bulk Metallic Glass, Liquidus Line, Ternary Eutectic
ISSN: 1543-1940
Cilt: 41
Sayı: 7
Sayfa: 1699-1705
Sınıflandırma :
25
The aging behavior of homogenized type 308 and 308CRE stainless steel
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
J. M. Vitek , S. A. David
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
Yayıncı Web Sitesi Tam Metin
Kaydet
The aging behavior of type 308 stainless steel and type 308 stainless steel with controlled residual elements (308CRE) was studied. The alloys were initially homogenized, resulting in a fully austenitic structure in the type 308 alloy and a duplex, austenite plus ferrite structure in the type 308CRE alloy. The materials were subsequently aged at 550, 650, 750, and 850 °C for times up to 10,000 hours. Aging of the type 308 steel resulted in precipitation of chromium-rich M23C6, primarily along grain boundaries, followed by sigma-phase formation after long aging times (≥5000 hours). The aging response of the duplex type 3O8CRE steel was somewhat more complicated. Although the titaniumrich carbides, nitrides, and sulfides produced during homogenization remained stable during subsequent aging, some additional precipitation was found. G-phase formed within the residual ferrite but eventually redissolved. The ferrite partially dissolved during early aging and later transformed to sigma phase. The sigma-phase formed significantly faster in the aged type 308CRE alloy. The results are summarized in the form of TTT diagrams. A comparison is made with a similar aging study on the same alloys but starting with the as-welded condition.
DOI : 10.1007/BF02647189
Anahtar Kelimeler : Ferrite, Austenite, Metallurgical Transaction, Weld Metal, Aging Time
ISSN: 1543-1940
Cilt: 18
Sayı: 7
Sayfa: 1195-1201
Sınıflandırma :
26
EBSD Study on the Effect of a Strong Axial Magnetic Field on the Microstructure and Crystallography of Al-Ni Alloys During Solidification
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Xi Li , Yves Fautrelle , Annie Gagnoud , Rene Moreau , Dafan Du , Zhongming Ren , Xionggang Lu
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Yıl :
2016
Metallurgical and Materials Transactions A
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Kaydet
The effect of a strong magnetic field on the microstructure and crystallography of the primary and eutectic Al3Ni phases in Al-Ni alloys was investigated by using EBSD. The results show that the magnetic field significantly affected the microstructures and crystallography during both volume and directional solidification. As a result, the Al3Ni primary phases were aligned with the 〈001〉 crystal direction along the magnetic field and formed a layer-like structure. The magnetic field intensity, solidification temperature, growth speed, and alloy composition played important roles during the alignment process of the Al3Ni primary phase. Indeed, the alignment degree increased with the magnetic field and the solidification temperature during normal solidification. Moreover, the effect of the magnetic field on the crystallography of the Al-Al3Ni eutectic in the Al-Ni alloys was also studied. The applied magnetic field modified the orientation of the preferred growth direction of the Al3Ni eutectic fiber and the crystallographic orientation relationship of the Al-Al3Ni eutectic. The orientation of the preferred growth direction of the Al3Ni eutectic fiber depended mainly on the solidification direction and the alignment of the Al3Ni primary phase. Furthermore, a method for controlling the crystallization process by adjusting the angle between the solidification direction and the magnetic field was proposed.
DOI : 10.1007/s11661-015-3279-4
Anahtar Kelimeler : Al3Ni, Solidification Direction, Strong Magnetic Field, Magnetic Field Intensity, Magnetic Field Direction
ISSN: 1543-1940
Cilt: 47
Sayı: 3
Sayfa: 1180-1197
Sınıflandırma :
27
Structure and properties of a β solution treated, quenched, and aged si-bearing near-α titanium alloy
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
G. Sridhar , D. S. Sarma
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
The microstructure, tensile properties, and fractographic features of a near-α titanium alloy, IMI 829(Ti-6.1 wt pct Al-3.2 wt pct Zr-3.3 wt pct Sn-1 wt pct Nb-05 wt pct Mo-0.32 wt pct Si) have been studied after aging over a temperature range of 550°C to 950°C for 24 hours following solution treatment in the β phase field at 1050°C and water quenching. Transmission electron microscopy studies revealed that aging at 625°C and above produced discrete silicides at α′ interplatelet boundaries. However, aging at 900°C and above has also resulted in the precipitation of β phase along the lath boundaries of martensite. The silicides have been found to have a hexagonal structure withc=0.36 nm anda=0.70 nm (designated as S2 by earlier workers). There is a significant improvement in yield and ultimate tensile strength after aging at 625°C, but there is less improvement at higher aging temperatures. The tensile ductility is found to be drastically reduced. While the fracture surface of the unaged specimen shows elongated dimples, the aged samples show a mixed mode of fracture, consisting of facets, featureless parallel bands, and extremely fine dimples.
DOI : 10.1007/BF02647493
Anahtar Kelimeler : Martensite, Metallurgical Transaction, Titanium Alloy, Ultimate Tensile Strength, Aging Temperature
ISSN: 1543-1940
Cilt: 20
Sayı: 1
Sayfa: 55-62
Sınıflandırma :
28
Hydride embrittlement and irradiation effects on the hoop mechanical properties of pressurized water reactor (PWR) and boiling-water reactor (BWR) ZIRCALOY cladding tubes: Part III. Mechanical behavior of hydride in stress-relieved annealed and recrystallized ZIRCALOYs at 20 °C and 300 °C
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
Sylvie Arsene , Jinbo Bai , Philipe Bompard
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
This series of articles on the hydride embrittlement effect in ZIRCALOYs consists of three parts. Part III deals with the mechanical properties of some hydrides in some ZIRCALOYs at two temperatures (20 °C and 300 °C). The damage and fracture mechanisms were investigated by SEM in-situ testing. Based on the scanning electron microscopy (SEM) in-situ observations and the mechanical modeling, the mechanical behavior of hydrides confined within a matrix was determined. The hydrides can undergo significant plastic deformation under certain conditions. They have higher strength than the surrounding ZIRCALOY matrix. The radiation effect on hydrided ZIRCALOYs and the combined effect were also discussed. Part I is concerned with the general influence of hydrides on the mechanical properties and damage and fracture mechanisms of ZIRCALOYs at two temperatures (20 °C and 300 °C) and for hydrogen content up to 4500 ppm. In Part II, the morphology and crystallographic structure of hydrides in two ZIRCALOYs are examined at different magnifications and by different techniques (SEM, transmission electron microscopy (TEM), and X-ray diffraction) as a function of their pre-heat treatment and their hydrogen content.
DOI : 10.1007/s11661-003-0093-1
Anahtar Kelimeler : Hydride, Material Transaction, Hydrogen Content, Irradiate Material, Matrix Deformation
ISSN: 1543-1940
Cilt: 34
Sayı: 3
Sayfa: 579-588
Sınıflandırma :
29
The occurrence of aligned microstructures in directionally solidified aluminum-bismuth alloys
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
R. N. Grugel , A. Hellawell
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
Yayıncı Web Sitesi Tam Metin
Kaydet
DOI : 10.1007/BF02643357
Anahtar Kelimeler : Bismuth, Interdiffusion Coefficient, Directionally Solidify, Monotectic Alloy, Tracer Diffusion Data
ISSN: 1543-1940
Cilt: 13
Sayı: 3
Sayfa: 493-495
Sınıflandırma :
30
Transient oxidation of Single-Crystal β-NiAl
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Yayıncı :
Metallurgical and Materials Transactions A
Yazar(lar) :
J. Doychak , J. L. Smialek , T. E. Mitchell
Konu :
Metallic Materials, Characterization and Evaluation of Materials, Structural Materials, Surfaces and Interfaces, Nanotechnology
Metallurgical and Materials Transactions A
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Kaydet
The transient oxidation of β-NiAl in air at 800 °C and 1100 °C has been studied using electron microscopy. The oxide scale consists predominatly of metastable Al2O3 phases. θ-Al2O3 is the major oxide phase within 10.0 hr of oxidation at 800 °C and 0.1 hr at 1100 °C. The scales form epitaxially on (001)β and (012)β specimens throughout the transient stage, whereas the degree of preferred oxide orientation decreases with oxidation time on (011)β and (111)β specimens. The orientation relationships reflect the small mismatch between parallel close-packed directions in the metal and in the cation sublattice of the oxides. The correlation of distinctive oxide surface morphologies with internal structural defects indicates the strong tendency of the Al2O3 scale to growvia short-circuit diffusion paths.
DOI : 10.1007/BF02653930
Anahtar Kelimeler : Metallurgical Transaction, Oxide Scale, Orientation Relationship, Select Area Diffraction Pattern, Cation Vacancy
ISSN: 1543-1940
Cilt: 20
Sayı: 3
Sayfa: 499-518
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