Journal Article

Effect of Zn on microstructure evolution of Mg-Gd-Y-Nd-Zn-Zr alloy during heat treatment

Qu, J, Li, T, Chen, D J, Yuan, J W, Liu, W

2019

Overview

The effect of Zn on the microstructure evolution of Mg-7Gd-3Y-1Nd-xZn-0.5Zr (x=1.0, 2.0) (wt.%) alloys during homogenization and ageing heat treatment has been investigated systemically. The results indicate that as-cast 1 Zn alloy is composed mainly of α-Mg, Mg5(RE, Zn) eutectic phase, (Mg, Zn)3RE eutectic phase, stacking faults and block-like compounds rich in RE. Increasing of Zn content result in the disappearance of Mg5(RE, Zn) eutectic phase, but the volume fraction of 14H-typ LPSO phase is increasing, which has made it even more difficult to dissolve into the matrix during homogenization. After homogenization at 520 °C for 48 h, the 14H LPSO phase remains in the alloys with 2 wt.% Zn, but only compounds rich in RE can be seen in the alloy with 1 wt.%Zn. After ageing at 240°C for 18 h, the coherent β′ phase can be found both in 1Zn and 2Zn alloys, resulting in the increase of mechanical properties. The β′, β1 and stacking faults can be found in 1Zn and 2Zn alloys after ageing at 240°C for 100 h. However, it can be concluded that Zn can suppress the formation of LPSO phases but impede the precipitation of β′ and β1 during the aging process. The as-aged alloy with 1% Zn addition shows the optimal mechanical properties.

• Publisher: IOP Publishing
• Subject: Aging / Aging (metallurgy) / Alloys / Eutectics / Evolution / Gadolinium / Heat treatment / Homogenization / Magnesium / Mechanical properties / Microstructure / Stacking faults / Zinc base alloys / Zirconium base alloys