Collective behavior of strain-induced martensitic transformation (SIMT) in biomedical Co-Cr-Mo-N alloy polycrystal: An ex-situ electron backscattering diffraction study

Collective behavior of strain induced martensitic transformation (SIMT) in biomedical Co-Cr-Mo-N alloy polycrystal has been investigated by ex-situ electron backscattering diffraction (EBSD) analysis during tensile deformation. The formation of SIMTed ε-hcp phase depends on the crystal orientation, and the SIMT behavior is basically understood by the motion of isolated Shockley partial dislocation associated with the negative stacking fault energy (SFE) of this alloy. However, their variant selection is not governed by Schmid׳s law. Most of SIMT occurred in grains with loading axes near and between 〈1 1 1〉 and 〈0 1 1〉 directions because of the low effective SFE, which is determined by the difference in the Schmid factors for leading and trailing Shockley partial dislocations. In grains with loading axes near the 〈0 0 1〉 direction, the SIMT did not occur due to the high value of the effective SFE. These findings are very important to improve the strength and wear resistance of this alloy without sacrificing the ductility by controlling the crystal texture.