Fabrication of high-strength Mg-Gd-Zn-Zr alloy via selective laser melting

Mg-11.00Gd-1.77Zn-0.43Zr (wt.%) alloy named GZ112K was prepared by selective laser melting (SLM) with different processing parameters. The formability, element vaporization, microstructure and tensile properties of the SLMed samples at different scanning speed and hatch spacing were characterized. The process map at a constant laser power of 80 W for the alloy has been established. It shows that the optimum scanning speed and hatch spacing are 300-700 mm/s and 100 mu m respectively. The SLMed samples have fine grains of about 2 mu m and dispersed eutectic phase of beta-(Mg,Zn)(3)Gd due to the very high cooling rate, high solid solubility of Gd and Zn elements in alpha-Mg matrix owing to the effect of solute trapping. The SLMed GZ112K alloy with scanning speed of 300 mm/s and hatch spacing of 100 mu m has yield strength (YS) of 325 MPa, ultimate tensile strength (UTS) of 332 MPa and elongation of 4.0% at room temperature. Compared with as-cast alloy, the SLMed GZ112K alloy has much higher YS (+162 MPa), UTS (+122 MPa) and comparable elongation (+0.4%).