Precipitation microstructure and their strengthening effects of an Mg–2.8Nd–0.6Zn–0.4Zr alloy with a 0.2 wt.% Y addition

A micro-alloy addition of Y (0.2 wt.%) produced a significant improvement in the tensile yield strength of an Mg–2.8Nd–0.6Zn–0.4Zr (wt.%) alloy at 200 °C, with a 28% increase from 143 MPa to 183 MPa. APT characterisation confirmed that small solute clusters in a high number density were present in the as-quenched sample. TEM examinations revealed that β-type precipitates habiting on prism { 1   1   2 ¯   0 } planes were dominant in the sample after aged for 14 h at 200 °C, and they co-existed with γ-type precipitates on the basal plane of Mg matrix. The precipitation sequence of β-type precipitates is solute clusters → β″ → β′ → β1 before the peak hardness. There was significant clustering of solutes in the Y-containing alloy, but Y did not clearly partition into clusters or precipitates and remained in the Mg matrix. β″, β′ and β1 were measured with stoichiometric Mg9(Nd,Zn), Mg4(Nd,Zn) and Mg2(Nd,Zn), respectively.