Orientation relationships between phases arising during compression testing in ZrO2-TRIP-steel composites

The martensitic transformations taking place during the compressive deformation of a TRIP-steel matrix with zirconia particles are investigated using EBSD, and the orientation relationships are discussed. In the TRIP-steel matrix, the mutual orientation of austenite and s-martensite fulfils the Shoji-Nishiyama orientation relationship perfectly, whereas the gamma-alpha' transformation is characterised by the Kurdjumow-Sachs orientation relationship with a small deviation. This behaviour is attributed to the different formation mechanisms of epsilon- and alpha'-rnartensites. Whereas the s-martensite is interlaced through faulting of the austenite crystal lattice, alpha'-martensite forms new domains. Particularly at the void-free interfaces between the TRIP-steel and the ceramic particles in virgin samples, the external load can be transferred to the ceramic particles. As a consequence, a stress induced phase transformation within the MgO partly stabilised ZrO2 can be observed. Different observed orientation relationships in ZrO2 are discussed with respect to two possible t-ZrO2 unit cell choices. Slight deviations from the ideal orientation relationship of approximately 1-2 degrees are necessary for a better coherence between t-ZrO2 and m-ZrO2 because of their lattice misfit. The resulting mechanical properties are shown in context to the arising volume fraction of the martensitic phases. (C) 2012 Elsevier B.V. All rights reserved.