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Vol.42, No.6, 455 ~ 464, 2004
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| Title |
| Effects of Volume Fraction of Tempered Martensite on Dynamic Deformation Properties of Ti-6Al-4V Alloy Having Bimodal Microstructure |
| 이동근 Dong Geun Lee , 이유환 You Hwan Lee , 이종수 Chong Soo Lee , 이성학 Sung Hak Lee |
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| Abstract |
| The effects of volume fraction of tempered martensite on quasi-static tensile and dynamic deformation properties of Ti-6Al-4V alloy with bimodal microstructure were investigated in this study. Five microstructures with various tempered martensite volume fractions were obtained by varying heat-treatment temperatures and times. Dynamic torsional tests were conducted on them by using a torsional Kolsky bar. The test data were analyzed in relation to microstructures, tensile properties, and adiabatic shear band formation. Under a dynamic loading condition, maximum shear stress increased with increasing tempered martensite volume fraction, whereas fracture shear strain decreased. Observation of the deformed area beneath the fracture surface after the dynamic torsional test indicated that a number of voids initiated mainly at a/martensite interfaces, and that the number of voids increased with increasing martensite volume fraction. Adiabatic shear bands of 6-10 lam in width were formed in the specimens having lower martensite volume fractions, while they were not formed in those having higher martensite volume fractions. The possibility of the adiabatic shear band formation was explained by concepts of absorbed deformation energy and void initiation. (Received April 7, 2004) |
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| Key Words |
| Ti-6Al-4V alloy, Tempered martensite, Bimodal structure, Dynamic torsional test, Adiabatic shear band |
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