Effects of Li Addition on Microstructure and Mechanical Properties of Rapidly Solidified Mg96.5Gd2.5Zn1 Alloy

The effects of different amounts of Li addition on the microstructure and mechanical properties of rapidly solidified Mg96.5Gd2.5Zn1 alloy were investigated. The results indicate that the supersaturation of Gd and Zn solute atoms of the as-cast alloys decreases in the Mg matrix grains, and the (Mg, Zn) 3Gd precipitates located at the grain boundaries increase and the grain size of Mg matrix decreases with the Li addition. After solid-solution treatment, the formation of 14H type of long-period stacking phase in the alloys is inhibited and the nano- or submicron (Mg, Zn) 3Gd phase precipitates in large amounts with the increase of Li addition. And as the Li content is 7.6 at%, the volume fraction of LPSO phase in the alloy declines dramatically. After hot extrusion deformation, the block 14H phase in the alloys is kinked and delaminated, and the lamellar 14H dissolves to some extent in the matrix. (Mg,Zn)3Gd phase is fragmented and refined, and different degrees of recrystallization occur in the matrix. Mg96.5Gd2.5Zn1 alloy exhibits the best comprehensive mechanical properties with the Rm=325 MPa and the δ=9.5%, whereas the mechanical properties of the alloys with Li addition decline gradually with the increase of Li addition. The microstructure evolution mechanism and mechanical behavior response under various conditions were analyzed. © 2018, Science Press. All right reserved./Copyright © 2018, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.