Microstructure, mechanical properties and fracture mechanism of Ti2AlC reinforced AZ91D composites fabricated by stir casting

Mg-alloy (AZ91D) based composites reinforced by Ti2AlC MAX phases particles were firstly fabricated by the stir casting technology. The mechanical properties in relationship with the microstructure were carefully investigated. The Ti2AlC particles were generally distributed along α-Mg grain boundaries and strongly impeded the dendritic growth of α-Mg. Yield strength, Vikers hardness, ultimate compressive strength, and Young's moduli increased with increasing Ti2AlC fraction in composites, while the optimized ultimate tensile strength was found for 10 vol% of Ti2AlC. The theoretical calculation on tensile yield strength reveals that individual strengthening contribution was mainly from Hall-Petch strengthening and Forest strengthening, followed by Orwan strengthening effect. The elastic moduli were predicated by Halpin-Tsai approach the mixture rule and the Hashin and Shtrickman equation. One aspect ratio of 3 was found by fitting Halpin-Tsai approach with experimental results. In-situ tensile test revealed the cracks were initiated in Ti2AlC particles and propagated along α-Mg grain boundaries. During this process, no decohesion occurred at the Ti2AlC and AZ91D interfaces.