Partially stabilized zirconia exhibits a stress-assisted martensitic phase transformation from the cubic/tetragonal phase into the monoclinic phase, which is accompanied by a volume dilation. In similar way, metastable austenitic steels show a deformation-induced martensitic phase transformation of the metastable austenite into alpha’-martensite via an intermediate state of epsilon-martensite during mechanical loading. The combination of both phase transformations are responsible for toughening of metal matrix composites consisting of these two components. The acoustic emission (AE) technique provides real-time information on the localized processes of plastic deformation, martensitic phase transformation as well processes of damage and fracture as shown already for TRIP steels where AE is associated with dislocation motion, formation of stacking faults and formation of alpha’-martensite. In the present work, the AE analysis is applied to partially stabilized zirconia and particle reinforced TRIP steels under compressive loading. Here, the in situ kinetics of the stress-assisted phase transformation as well of the damage process of zirconia obtained from AE data is of particular interest. To bridge the results of AE in situ examination and microstructure evolution, the phase transformations were analysed in addition by XRD and EBSD measurements.