Influence of Heat Treatment on the Mechanical Properties and Damage Development in a SiC/Ti-15-3 MMC

Titanium alloys are commonly heat-treated to meet specific design requirements. In an effort to possibly create a better composite, the influence of heat treatments on the damage evolution and strength of a SiC/Ti metal matrix composite (MMC) was studied. Heat treatments of 450°C and 700°C for 24 hours were performed on axial and transverse unidirectional specimens. These specimens, in addition to specimens in the as-received condition, were tested under non-proportional loading paths and then microstructurally analyzed to determine the induced damage state. It has been found that different heat treatments effected the elastic modulus and the macroscopic yield stress, as well as the stiffness reduction due to damage evolution. The axial composite with a 24-hr. heat treatment at 450 °C showed the highest elastic modulus and the lowest stiffness reduction than the other heat treatment conditions. The transverse composite in the as-received condition showed the highest room temperature elastic modulus and a low stiffness reduction compared with other heat treatment conditions. Typical damage modes of Ti MMC's, such as fiber matrix debonding and matrix microcracking, were seen in all three microstructural conditions. A micromechanics model based on the MoriTanaka averaging scheme was implemented to model the combined effects of damage and plasticity.