Effect of gadolinium on aged hardening behavior, microstructure and mechanical properties of Mg-Nd-Zn-Zr alloy

Mg-3.4Nd-0.1Zn-0.40Zr alloy samples with and without containing gadolinium (0.6%, mass fraction) were prepared by sand casting. The aged hardening behavior, solidification microstructures and mechanical properties of the alloys were investigated by using the analysis methods of OM, XRD, TEM, hardness tests and mechanical property tests. The main research results are as follows. 1) Compared with the alloy without the addition of gadolinium, the alloys with the addition of gadolinium shows the more remarkable age-hardening response. 2) The as-cast microstructure of the alloy with and without containing gadolinium consists of α-Mg grains with Mg₁₂Nd phase on the grain boundary. After solution heat-treatment, Mg₁₂Nd phase of the alloy without containing gadolinium is dissolved in the matrix, however, there is still discontinued Mg₁₂Nd phase at grain boundary of the alloy with containing gadolinium. The more finely dispersed precipitates in Mg matrix are formed in the alloy with containing gadolinium during age-treatment. 3) The room temperature and high temperature mechanical properties of the alloy are satisfactory, with σ_b=280 MPa, σ_0.2=165 MPa at RT and σ_b=215 MPa, σ_0.2=155 MPa at 250°C. The high temperature mechanical properties decrease slightly with the increase of temperature.