TEM observation of dynamic distortion in 2Y-PSZ/steel composites

2Y-PSZ/steel composites have been sintered by vacuum hot-pressing. The microstructure was studied by TEM after the composites were impacted at the average strain of 1.0 × 10³ S^-1 by split Hopkinson method. The results showed that the phase transformation from γ to α′ occurred in the matrix of TRIP steel under dynamic loading. Dynamic mechanical properties of 2Y-PSZ/steel composites were improved because of the transformation of distortion induced Martensite. The morphology of Martensite induced by distortion was mainly twins. The sub-structure of Martensite was mainly twins. But there was no mid-ridge and distortion twins comptetely expanded to the whole Martensite. Moreover, there was dislocation Martensite at the same sample. The inhomogeneous spread of stress wave in 2Y-PSZ/steel composites led to the different dimension of twins Martensite. When dynamic distortion was relatively efficient, Martensitic dimension and twins distance were increased and the second twins would occur. ZrO₂ grains are finely distributed in matrix TRIP steel, which improved the dynamic flow stress of 2Y-PSZ/steel composites. Moreover, ZrO₂ could undergo tetragonal→monoclinic phase transformation, which would improve the dynamic yield strength of the composites. But when the content of ZrO ₂ exceeded 20 vol.%, it would restrain the transformation of dynamic distortion induced Martensite in TRIP steel and led to the decrease of the dynamic mechanical properties of 2Y-PSZ/steel composites.