Effect of TiB2 particles on the microstructure and mechanical properties of Al-Si-Cu-Mg-Ni alloy fabricated by powder metallurgy

The mechanical properties of Al-11Si-3Cu-2Ni-1 Mg alloy (M142 alloy) are significantly affected by grain size, Si phase and intermetallic phase size and distribution. Therefore, the regulation of microstructure is very important to improve the mechanical properties of the alloy. In this work, high performance TiB₂/M142 composites were prepared by powder metallurgy and hot extrusion. The results show that TiB₂ particles can effectively refine the grain and the second phase, and induce more intragranular intermetallic phases. With the increase of TiB₂ content, the strength increased continuously, but the ductility increased first and then decreased. The improvement of the strength of the composites are mainly attributed to thermal mismatch strengthening. The first increase in ductility is mainly due to the capture and pin of the dislocation by intragranular intermetallic phases, which makes the grains have stronger dislocation accumulation and storage capacity. The subsequent reduction in ductility is mainly attributed to the local stress concentration in the TiB₂ agglomeration region, which eventually leads to the rapid failure of the composites.