Influence Of Solution Treatment Time On Precipitation Behavior And Mechanical Properties Of Mg-2.0nd-2.0sm-0.4zn-0.4zr Alloy

The effect of solution treatment time on the microstructure and mechanical properties of aged the Mg-2.0Nd-2.0Sm-0.4Zn-0.4Zr (wt.%) alloy were investigated to give full play to the performance of the alloy. As the solution treatment time increased from 2 h to 12 h at 788 K, the grain size of the solution-treated alloy significantly increased, and the network-like beta-Mg-12(Nd, Sm, Zn) phase gradually dissolved into the alpha-Mg matrix. It should be noted that no obvious residual beta phase can be observed when the solution treatment time was more than 8 h. After the solution-treated alloy was further aged at 473 K for 18 h, a large number of nanoscale precipitates were observed in the alpha-Mg matrix. The solution treatment time was 2 h, the alpha-Mg matrix mainly consisted of spherical-shaped and basal plate-shaped precipitates. Upon the increase of solution treatment time to 8 h, the key strengthening phases transformed from spherical-shaped precipitates and basal plate-shaped precipitates to prismatic plate-shaped beta ' precipitates. The orientation relationship between beta ' precipitates and alpha-Mg matrix was ((1) over bar 10)(beta ') // (1 (1) over bar 00)(alpha) and [112](beta ') // the [22 (4) over bar3](alpha). Further increasing of solution treatment time from 8 h to 12 h, the key strengthening phases mainly were still beta ' precipitates. The solution treatment of aged alloy was carried out at 788 K for 8 h, which achieved optimal ultimate tensile strength (UTS) of 261 +/- 4.1 MPa, yield strength (YS) of 154 +/- 1.5 MPa, and elongation of 5.8 +/- 0.1%, respectively.