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Hirohiko Takuda - One of the best experts on this subject based on the ideXlab platform.
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Work Hardening behaviors of magnesium alloy sheet during in plane cyclic loading
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Takayuki Hama, Yuhta Kariyazaki, Naohiro Hosokawa, Hitoshi Fujimoto, Hirohiko TakudaAbstract:Abstract This paper presents the Work-Hardening behaviors of a rolled AZ31B magnesium alloy sheet during in-plane cyclic loading. The overall trend of the stress–strain curve was as follows. As established before, the yield stress under compression was considerably less than that under tension, and an inflected shape was observed in the stress–strain curve during the subsequent tension. Furthermore, an asymmetric evolution of Work-Hardening was observed as follows. The rate of Work-Hardening in the late stage of compression became gradually large with an increase in the number of cycles. Owing to this increase in the rate of Work-Hardening, the stress at the end of compression increased as the number of cycles increased. On the other hand, the rate of Work-Hardening in the late stage of tension became small as the number of cycles increased, yielding a decrease in the stress at the end of tension with the increase in the number of cycles. The results were almost the same when the cyclic loading test was carried out after tensile strain was applied to the sheet. On the other hand, when the cyclic loading test was carried out after compressive strain was applied, the increase in the rate of Work-Hardening in the late stage of compression was significantly more pronounced, whereas the inflected shape of the curve during tension was considerably less pronounced. The mechanisms of the above macroscopic behaviors were investigated in terms of twinning.
Mamoun Medraj - One of the best experts on this subject based on the ideXlab platform.
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Modelling of Work-Hardening behaviour for laser welded magnesium alloy
International Journal of Materials Research, 2008Co-Authors: Mohammad Jahazi, H. Al-kazzaz, Mamoun MedrajAbstract:Abstract To investigate the reliability of the laser welding process for the magnesium alloy ZE41A-T5, eight butt joints were welded using the same processing parameters. These joints were tensile tested in the as-welded and aged conditions and the tensile data were analyzed from Work-Hardening characteristics. The flow curves cannot entirely be satisfactorily described by the Kocks–Mecking model; however, the model is still applicable to the high strain zone of the flow curves where Work-Hardening rate decreases linearly with flow stress. The reproducibility of the initial Work-Hardening rate and saturation stress is statistically analyzed. The initial Work-Hardening rates for the base castings and welded joints vary from approximately 4000 to 7000 MPa, i. e. 1/4 to 1/3 of the base material shear modulus. The as-welded joints have slightly higher initial Work-Hardening rates than the base castings. Artificial aging produces lower initial Work-Hardening rates compared with the base material. The saturatio...
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Modelling of Work-Hardening behaviour for laser welded magnesium alloy
International Journal of Materials Research, 2008Co-Authors: Xinjin Cao, H. Al-kazzaz, Mohammad Jahazi, Mamoun MedrajAbstract:To investigate the reliability of the laser welding process for the magnesium alloy ZE41A-T5, eight butt joints were welded using the same processing parameters. These joints were tensile tested in the as-welded and aged conditions and the tensile data were analyzed from Work-Hardening characteristics. The flow curves cannot entirely be satisfactorily described by the Kocks–Mecking model; however, the model is still applicable to the high strain zone of the flow curves where Work-Hardening rate decreases linearly with flow stress. The reproducibility of the initial WorkHardening rate and saturation stress is statistically analyzed. The initial Work-Hardening rates for the base castings and welded joints vary from approximately 4000 to 7000 MPa, i.e. 1/4 to 1/3 of the base material shear modulus. The aswelded joints have slightly higher initial Work-Hardening rates than the base castings. Artificial aging produces lower initial Work-Hardening rates compared with the base material. The saturation stress ranges approximately from 260 to 320 MPa, i.e. about 2% of the shear modulus. The saturation stress for the welded joints is lower than that for the base material. Compared with the as-weld joints, aging decreases initial Work-Hardening rate but slightly increases saturation stress. Both initial Work-Hardening rate and saturation stress become more scattered after aging.
J. Pietikäinen - One of the best experts on this subject based on the ideXlab platform.
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Low rate of Work-Hardening at the tempered martensite embrittlement area
Scandinavian Journal of Metallurgy, 1997Co-Authors: J. PietikäinenAbstract:The effects of the low rate of Work-Hardening have been presented as at least one reason for the tempered martensite embrittement. A quench and tempering steel, in common use, was studied after austenitizing, quenching and tempering into the different conditions for the purpose of sheding new light on the low rate of Work-Hardening in the tempering temperature area of about 350°C. The mechanical tests were done by a low-speed torsion test. The broken specimens were studied by the carbon replica method in TEM. It was observed that in the region of tempering at 350°C, the τ-tgγ-curves have, just after yielding, an extensive plateau where the rate of Work-Hardening was nil or even negative. After the plateau, and before the breaking of the specimen, the rate of Work-Hardening was positive. This form of the τ-tgγ-curves was not sensitive to the coarseness of the martensitic structure or the moderate increase in test speed. It was observed that the Fe3C-plates deformed and turned their habit planes to the direction of the slip during deformation. No breaks in the carbide plates were seen. A model for the low rate of Work-Hardening was presented in which the turn of the Fe 3 C-plates compensates for the effect of the increasing number of dislocations.
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Significance of Rate of Work Hardening in Tempered Martensite Embrittlement
Journal de Physique IV Colloque, 1995Co-Authors: J. PietikäinenAbstract:The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of Work Hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe3C appear in quite different tempering temperature ranges. The Ms temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of Work Hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of Work Hardening are considered.
Shiro Torizuka - One of the best experts on this subject based on the ideXlab platform.
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Prediction of the Work-Hardening exponent for ultrafine-grained steels
Materials Science and Engineering: A, 2012Co-Authors: Hai Qiu, Toshihiro Hanamura, L.n. Wang, Shiro TorizukaAbstract:Abstract The Work-Hardening exponent is used to quantify the Work-Hardening of ultrafine-grained steels. The exponent for the types of steel with the carbon content below 0.22 wt% is proposed to be directly predicted by either yield strength or ferrite grain size. The exponent's value linearly decreases with increasing yield strength or D −1/2 (where D is the ferrite grain size), and becomes zero when yield strength is higher than 620 MPa (or D is less than 1 μm).
Takayuki Hama - One of the best experts on this subject based on the ideXlab platform.
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Work Hardening behaviors of magnesium alloy sheet during in plane cyclic loading
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Takayuki Hama, Yuhta Kariyazaki, Naohiro Hosokawa, Hitoshi Fujimoto, Hirohiko TakudaAbstract:Abstract This paper presents the Work-Hardening behaviors of a rolled AZ31B magnesium alloy sheet during in-plane cyclic loading. The overall trend of the stress–strain curve was as follows. As established before, the yield stress under compression was considerably less than that under tension, and an inflected shape was observed in the stress–strain curve during the subsequent tension. Furthermore, an asymmetric evolution of Work-Hardening was observed as follows. The rate of Work-Hardening in the late stage of compression became gradually large with an increase in the number of cycles. Owing to this increase in the rate of Work-Hardening, the stress at the end of compression increased as the number of cycles increased. On the other hand, the rate of Work-Hardening in the late stage of tension became small as the number of cycles increased, yielding a decrease in the stress at the end of tension with the increase in the number of cycles. The results were almost the same when the cyclic loading test was carried out after tensile strain was applied to the sheet. On the other hand, when the cyclic loading test was carried out after compressive strain was applied, the increase in the rate of Work-Hardening in the late stage of compression was significantly more pronounced, whereas the inflected shape of the curve during tension was considerably less pronounced. The mechanisms of the above macroscopic behaviors were investigated in terms of twinning.
