Effect of La₂O₃ on Microstructure and Mechanical Properties of Mg–3Y Alloy

The preparation of high-performance rare earth magnesium (Mg–RE) alloy still heavily relies on expensive master alloy as a critical raw material. In order to address this issue, a series of Mg–3Y–xLa₂O₃ (x = 0, 0.5, 1, 1.5, 2, and 2.5 wt%) alloys were fabricated utilizing cost-effective rare earth oxides (RE_mO_n). The effect of La₂O₃ on the microstructure and mechanical properties of the alloys was thoroughly investigated. Upon the addition of La₂O₃ to the Mg–3Y alloy, in-situ reduction with Y results in the formation of numerous micron-sized Mg₁₇La₂ phases, which consequently alters the morphology and quantity of Mg₂₄Y₅ phase, as well as the grain size and (0001) basal texture intensity in Mg–3Y alloy. The Mg–3Y–1.5La₂O₃ alloy exhibits the highest mechanical strength [yield strength (YS) and ultimate tensile strength (UTS) increase by approximately 48.4 MPa and 36.1 MPa, respectively, compared to the Mg–3Y alloy] among all the samples tested. The primary strengthening mechanisms identified are grain boundary, texture, and second-phase strengthening. Moreover, the addition of La₂O₃ is observed to significantly increase the elongation (EL) of the alloy (Mg–3Y–0.5La₂O₃). However, the EL gradually decreases as La₂O₃ continues to increase.