On the role of selective nucleation and growth to recrystallization texture development in a Mg-Gd-Zn alloy

TL;DR

This study investigates how selective nucleation and growth during recrystallization influence texture development in a Mg-Gd-Zn alloy, revealing off-basal nuclei's dominance in texture evolution.

Contribution

It provides new insights into the nucleation sites and growth mechanisms that determine recrystallization texture in magnesium alloys with rare earth additions.

Findings

Off-basal nuclei grow and dominate the microstructure.

Basal nuclei diminish and eventually vanish during annealing.

Double-twin band recrystallization significantly influences texture.

Abstract

One of the main material properties altered by rare earth additions in magnesium alloys is texture, which can be specifically adjusted to enhance ductility and formability. The current study aims at illuminating the texture selection process in a Mg-0.073at%Gd-0.165at%Zn alloy by investigating recrystallization nucleation and early nucleus growth during static recrystallization. An as-cast sample of the investigated alloy was deformed in uniaxial compression at 200{\deg}C till 40% strain and was then cut into two halves for subsequent microstructure characterization via ex-situ and quasi in-situ EBSD investigations. In order to gain insights into the evolution of texture during recrystallization, the contributions from dynamic and static recrystallization were initially separated and the origin of the non-basal orientation of recrystallization nuclei was traced back to several potential nucleation sites within the deformed matrix. Considering the significant role of double-twin band recrystallization in determining the recrystallization texture, this type of recrystallization nucleation was further investigated via quasi-in-situ EBSD on a deformed sample, annealed at 400{\deg} for different annealing times. With progressive annealing a noticeable trend was observed, in which the basal nuclei gradually diminished and eventually vanished from the annealed microstructure. In contrast, the off-basal nuclei exhibited continuous growth, ultimately becoming the dominant contributors to the recrystallization texture. The study therefore emphasizes the importance of particular nucleation sites that generate favorably oriented off-basal nuclei, which over the course of recrystallization outcompete the neighboring basal-oriented nuclei in terms of growth, and thereby dominate the recrystallization texture.