Effects of volume fraction of tempered martensite on dynamic deformation properties of a Ti-6Al-4V alloy having a bimodal microstructure |
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Authors: | Dong-Geun Lee You Hwan Lee Chong Soo Lee Sunghak Lee |
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Affiliation: | (1) Center for Advanced Aerospace Materials, Pohang University of Science and Technology, 790-784 Pohang, Korea;(2) Center for Advanced Aerospace materials, Pohang University of Science and Technology, Pohang, Korea |
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Abstract: | The effects of the volume fraction of tempered martensite on the tensile and dynamic deformation properties of a Ti-6Al-4V
alloy having a bimodal microstructure were investigated in this study. Five microstructures having various tempered-martensite
volume fractions were obtained by varying heat-treatment conditions. Dynamic torsional tests were conducted on them 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, the maximum shear stress increased with increasing tempered-martensite volume
fraction, whereas the fracture shear strain decreased. Observation of the deformed area after the dynamic torsional test indicated
that a number of voids initiated mainly at α-phase/tempered-martensite interfaces, and that the number of voids increased
with increasing martensite volume fraction. Adiabatic shear bands of 6 to 10 μm 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 adiabatic shear-band formation was explained by concepts of absorbed deformation energy and void initiation.
jointly appointed with the Materials Science and Engineering Department, Pohang University of Science and Technology |
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