Stress-induced amorphization is a transformation induced plasticity
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Stress-induced amorphization has been recognized to be an efficient strain accommodating mechanism in several materials where usual plasticity mechanisms are inhibited, such as high lattice friction materials. Stress-induced amorphization is now apprehended as a deformation mechanism in its own right. The classical view of this process is the prior formation of the amorphous phase which then participate to the plastic deformation by flowing. In this presentation we will show that an important part of the plastic deformation related to this mechanism is, in fact, linked to the crystal to amorph phase transformation itself through the transformation induced plasticity (TRIP) mechanism. This finding is firstly supported by a series of molecular dynamics simulations of intragranular amorphous layer shearing highlighting the plastic anisotropy of this mechanism in forsterite, which is an orthorhombic ceramic with high lattice friction. In a second time, by combining molecular dynamics and finite elements simulations, we show that the strain produced by the phase transformation (amorphization) itself as to be taken into account for a first order description of the mechanical behavior of the whole process. Finally, we present a large-scale molecular dynamics simulation of forsterite polycrystal deformation in which grain boundary amorphization plays an important role on the plasticity of the system. The fine analysis of this simulation supports the findings that stress-induced amorphization should be considered as a phase transformation that produces plastic deformation.
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