Roles of Nd and Mn in a new creep-resistant magnesium alloy

• DOI: 10.1016/j.msea.2020.139152
• Publication Date: 2020-02-26T11:45:00Z
• Authors: Ning Mo; Ingrid McCarroll; Qiyang Tan; Anna Ceguerra; Julie Cairney; Hajo Dieringa; Yuanding Huang; Bin Jiang; Fusheng Pan; Michael Bermingham; Ming-Xing Zhang
• Keywords: Solid solution strengthening; Precipitation hardening; Atom probe; Hardening (computing)

Abstract Modification of the recently developed creep-resistant Mg-3Gd-2Ca (wt.%) magnesium alloy using Nd and Mn remarkably improved the creep resistance at both 180 °C and 210 °C . The modified Mg-2Gd-1Nd-2Ca-0.5Mn alloy after solid solution treatment exhibited outstanding creep resistance that is superior to the commercial creep-resistant Mg alloy, EV31, but contained less RE addition. The microstructural observations revealed that partial replacement of Gd with 1 wt% Nd did not enhance the effect of dynamic precipitates significantly. But further analysis by atom probe tomography verified the stronger co-segregation between Nd solute atoms and other solute atoms than that of Gd and Ca in the Mg solid solutions, leading to a higher solid solution strengthening effect on the creep resistance. The addition of 0.5 wt% Mn led to the formation of polygonal-shape α-Mn precipitates, which served as heterogeneous nucleants for dynamic precipitates, refining their size and increasing the number densities. As a result, the creep properties of newly developed Mg alloys were strengthened by a combination of improved solid solution strengthening by Nd and increased precipitation hardening by Mn addition.