Temperature-dependence of strengthening and wear mechanisms for GW42K alloy fabricated by wire-arc directed energy deposition

Abstract

Here, we investigated the microstructure, mechanical properties, and wear performance of Mg-4.6Gd-1.8Y-0.424Zr (wt.%) (GW42K) alloy fabricated using wire-arc directed energy deposition (WA-DED). The results indicate that the grains of the as-deposited alloy are equiaxed. There are many nanoscale β“ phases in the as-deposited alloy because of the cyclic thermal history. As the ambient temperature increases from 20 °C to 200 °C, affected by dynamic recrystallization, some fine grains appeared at the top of the worn sample, which promoted the wear mechanism of the alloy from mild plastic deformation to severe plastic deformation, thereby improving the high-temperature wear resistance of the alloy. After 200 °C/200 h artificial aging, β” precipitates change into β’ precipitates. According to the mechanical performance test at 200 °C, the yield strength of the alloy increases from 105.1 MPa to 161.3 MPa. Especially, the yield strength of the heat-treated alloy at 200 °C is higher than that at 20 °C, with increases of 17.1 %. By analyzing the strengthening mechanism caused by the β’ phase, it was confirmed that these two abnormal high-temperature strength phenomena are caused by the β’ phase. This work reveals the temperature dependence of the strengthening and wear mechanism of WA-DED GW42K alloy, which can provide a reference for the high-temperature application of Mg alloys.