Precipitate characteristics and precipitation-strengthening mechanism of Mg-13Gd-4Y–2Zn-0.6Zr alloy
Meng Mu, Genxing Lei, Honglei Zhang, Xuhui Zhang, Jianmin Yu
Abstract
In this study, the precipitate characteristics and precipitation-strengthening mechanism of solution-treated Mg-13Gd-4Y–2Zn-0.6Zr alloy after the upsetting and extrusion were investigated at different aging treatment temperatures. The prismatic plate-shaped nano-sized β′ precipitates and the prismatic rod-shaped micro-sized β precipitates were precipitated in low-temperature (e.g. 170 °C) and high-temperature (e.g. 330 °C) aging treatment, respectively. The critical nucleation resolved shear stresses (CRSSN) for the observed {10–12} and {11–21} extension twins and the twin number fractions of the two-type twins in the total twin number were unaffected by the precipitates. However, the greater total twin number in the alloy aged at 330 °C indicates that the strengthening effect of β precipitates on twinning was greater than that of β′ precipitates. The calculation results of Orowan equation showed that the strengthening effect of β′ precipitates on the pyramidal slip was greater than that of β precipitates. The greater hardness for the alloy aged at 170 °C was attributed to the greater strengthening effect of β′ precipitates on the pyramidal slip.