Correlation between dynamic recrystallization and formation of rare earth texture in a Mg-Zn-Gd magnesium alloy during extrusion

S H Lu,C Xu,R S Chen,E H Han,H Yan,T Nakata,S Kamado,M G Jiang,C S Lao

doi:10.1038/s41598-018-35170-4

Abstract

The trace addition of rare earth (RE) elements in Mg alloys can modify the extrusion texture, leading to the formation of RE texture and thus improved formability. The interrupted extrusion experiment as well as electron back-scatter diffraction (EBSD) characterization was conducted in Mg-1.5Zn-0.5Gd (wt.%) alloy to unveil the dominant dynamic recrystallization (DRX) mechanism and its correlation with the formation of RE texture during extrusion. The results indicate that continuous DRX (CDRX) dominated the microstructural development. Fresh DRXed grains with 30° [0001] grain boundaries preferentially nucleated in unDRXed grains with [10bar{{bf{1}}}0] basal fiber orientation via CDRX, showing preferred selection of [2bar{{bf{1}}}bar{{bf{1}}}0] basal fiber orientation rather than RE texture orientation. Consequently, CDRX contributed to the weakening of [10bar{{bf{1}}}0] basal fiber texture and had a more significant effect on the formation of [2bar{{bf{1}}}bar{{bf{1}}}0] basal fiber component than that of RE texture component. Besides, the preferred growth of recrystallized grains with RE texture orientation was confirmed to occur during static annealing after extrusion, which is inferred as the key reason for the formation of RE texture in dilute Mg-RE alloys.

Highlights

Commercial Mg alloys usually develop a strong basal fiber texture during hot extrusion process, which accounts for the unsatisfactory formability and ductility at room temperature
The continuous DRX (CDRX) is featured by the development of low angle grain boundaries (LAGBs) and their progressive rotation into high angle grain boundaries (HAGBs), and new grains, which is different from the discontinuous DRX (DDRX) involving classic nucleation and subsequent growth of new DRXed grains
Imandoust et al.[16] studied the effect of rare earth (RE) element on the recrystallization textures in Mg-Ce and Mg-Gd binary alloys and reported that CDRX facilitated the transformation of a sharp basal fiber texture into a randomized texture. Their following study[17] in the extruded Mg-Zn-Al-Y-MM (MM: Mischmetal) alloys revealed that CDRX sharpened the basal fiber texture and DDRX was shown to be the predominant mechanism for texture modification

Summary

Introduction

Commercial Mg alloys usually develop a strong basal fiber texture during hot extrusion process, which accounts for the unsatisfactory formability and ductility at room temperature. Imandoust et al.[16] studied the effect of RE element on the recrystallization textures in Mg-Ce and Mg-Gd binary alloys and reported that CDRX facilitated the transformation of a sharp basal fiber texture into a randomized texture Their following study[17] in the extruded Mg-Zn-Al-Y-MM (MM: Mischmetal) alloys revealed that CDRX sharpened the basal fiber texture and DDRX was shown to be the predominant mechanism for texture modification. Despite these efforts, there are still some differences of views on the DRX behavior in dilute Mg-RE alloys during extrusion and its corresponding contribution to the texture development. In this study interrupted extrusion experiment was designed for this Mg-Zn-Gd alloy, and electron back-scatter diffraction (EBSD) characterization was conducted to disclose the dominant DRX mechanism during extrusion and achieve a comprehensive understanding of the correlation between the DRX and the formation of RE texture for providing insightful knowledge into tailoring the texture formation and better designing new wrought Mg-RE alloys with high performance

Methods

Results

Conclusion