Effects of temperature, strain rate and grain size on the compressive properties of Ti 3SiC 2

Abstract

Herein we report on the response of polycrystalline Ti 3SiC 2 samples, with two grain sizes, on cyclic compressive loading in the 25–1200 °C temperature range. At lower temperatures, the stress–strain curves outline fully reversible, closed loops whose size and shape depend on grain size, but not strain rate. This phenomenon is attributed to the formation and annihilation of incipient kink bands, defined to be thin plates of sheared material bounded by opposite walls of dislocations that as long as the dislocation walls remain attached, are attracted to each other and annihilate upon removal of the load. Because the dislocations are confined to the basal planes, dislocation forests do not form and the dislocations can move reversibly over relatively large distances dissipating a significant (25% at 1 GPa) portion of the mechanical energy. At high temperatures (>1000 °C), the stress–strain loops are open, the response is strain rate dependent and cyclic hardening is observed for both microstructures. In this regime, kink bands and dislocation arrays interact in such a way as to form deformation cells that are smaller than the original grains and that, in turn, leads to hardening.