Effects of martensite morphology and volume fraction on quasi-static and dynamic deformation behavior of dual-phase steels |
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Authors: | Sangho Kim Sunghak Lee |
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Affiliation: | (1) the Center for Advanced Aerospace Materials, Pohang University of Science and Technology, 790-784 Pohang, Korea |
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Abstract: | The effects of martensite morphology and volume fraction on the quasi-static and dynamic deformation behavior of dual-phase
steels were investigated in this study. Quasi-static and dynamic torsional tests were conducted using a torsional Kolsky bar
for four steel specimens, which had different martensite morphology and volume fraction, and then the test data were compared
via microstructures, tensile properties, and fracture mode. In the intermediate quenched (IQ) steel specimens, very fine fibrous
martensites were well distributed in the ferrite matrix, but bulky martensites were mixed with ferrites in the step quenched
(SQ) specimens. Quasi-static torsional properties were similar to tensile properties, and fracture occurred in a ductile mode
in IQ specimens, whereas cleavage fracture was predominated in SQ specimens. Under a dynamic loading condition, the fracture
mode of SQ specimens was changed from cleavage to ductile fracture, whereas IQ specimens had a ductile fracture mode, irrespective
of loading rate. These phenomena were analyzed using a shear lag model, phase continuity, and the thermal softening effect
of martensite. |
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