Microstructure and mechanical properties of high strength Mg−15Gd−1Zn−0.4Zr alloy additive-manufactured by selective laser melting process

In order to verify the feasibility of producing Mg−rare earth (RE) alloy by selective laser melting (SLM) process, the microstructure and mechanical properties of Mg−15Gd−1Zn−0.4Zr (wt.%) (GZ151K) alloy were investigated. The results show that fine grains (~2 μm), fine secondary phases and weak texture, were observed in the as-fabricated (SLMed) GZ151K Mg alloy. At room temperature, the SLMed GZ151K alloy has a yield strength (YS) of 345 MPa, ultimate tensile strength (UTS) of 368 MPa and elongation of 3.0%. After subsequent aging (200 °C, 64 h, T5 treatment), the YS, UTS and elongation of the SLMed-T5 alloy are 410 MPa, 428 MPa and 3.4%, respectively, which are higher than those of the conventional cast-T6 alloy, especially with the YS increased by 122 MPa. The main strengthening mechanisms of the SLMed GZ151K alloy are fine grains, fine secondary phases and residual stress, while after T5 treatment, the YS of the alloy is further enhanced by precipitates.