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 (REmOn). 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.