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

Abstract

Abstract 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 ɛ -martensite fulfils the Shoji–Nishiyama orientation relationship perfectly, whereas the γ – α ’ transformation is characterised by the Kurdjumow–Sachs orientation relationship with a small deviation. This behaviour is attributed to the different formation mechanisms of ɛ - and α ’-martensites. Whereas the ɛ -martensite is interlaced through faulting of the austenite crystal lattice, α ’-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 ZrO 2 can be observed. Different observed orientation relationships in ZrO 2 are discussed with respect to two possible t-ZrO 2 unit cell choices. Slight deviations from the ideal orientation relationship of approximately 1–2° are necessary for a better coherence between t-ZrO 2 and m-ZrO 2 because of their lattice misfit. The resulting mechanical properties are shown in context to the arising volume fraction of the martensitic phases.