Optimizing the microstructures and enhancing the mechanical properties of AZ81 alloy by adding TC4 particles

In this work, AZ81 alloys reinforced with 3 wt%, 6 wt% and 9 wt% TC4 (Ti-6Al-4y) particles were fabricated using two-step stirring. The tensile results revealed that the TC4 particles could significantly improve the yield stress (YS), ultimate tensile stress (UTS), and elongation (El.) of AZ81 alloys. By adding TC4, the grains showed refined/coarse bimodal morphologies in the composites. The formation of beta (Mg17Al12) phase was notably suppressed due to the interfacial reaction between TC4 and Al. The dynamic recrystallization (DRX) behavior was also restricted by TC4 particles and beta phase, ascribing to the refined grains and Orowan strengthening. The good interfacial bonding was achieved at the interface of TC4/alpha-Mg in 6TC4/AZ81 composite. Compared to the AZ81, 6TC4/AZ81 showed the highest YS, UTS and El. of 241 MPa, 357 MPa, and 17.0%, respectively. Its increased strength was primarily attributed to the mismatch coefficient of thermal expansion (CTE) and grain boundary strengthening. The improved ductility was ascribed to the TC4 particles, which are more deformable to withstand external load.