Microstructure, Texture and Mechanical Properties of Mg-6Sn Alloy Processed by Differential Speed Rolling.

Kamil Majchrowicz,Bogusława Adamczyk-Cieślak,Witold Chromiński,Paweł Jóźwik,Zbigniew Pakieła

doi:10.3390/ma14010083

Abstract

The effect of shear deformation introduced by differential speed rolling (DSR) on the microstructure, texture and mechanical properties of Mg-6Sn alloy was investigated. Mg-6Sn sheets were obtained by DSR at speed ratio between upper and lower rolls of R = 1, 1.25, 2 and 3 (R = 1 refers to symmetric rolling). The microstructural and textural changes were investigated by electron backscattered diffraction (EBSD) and XRD, while the mechanical performance was evaluated based on tensile tests and calculated Lankford parameters. DSR resulted in the pronounced grain refinement of Mg-6Sn sheets and spreading of basal texture as compared to conventionally rolled one. The average grain size and basal texture intensity gradually decreased with increasing speed ratio. The basal poles splitting to transverse direction (TD) or rolling direction (RD) was observed for all Mg-6Sn sheets. For the as-rolled sheets, YS and UTS increased with increasing speed ratio, but a significant anisotropy of strength and ductility between RD and TD has been observed. After annealing at 300 °C, Mg-6Sn sheets became more homogeneous, and the elongation to failure was increased with higher speed ratios. Moreover, the annealed Mg-6Sn sheets were characterized by a very low normal anisotropy (0.91–1.16), which is normally not achieved for the most common Mg-Al-Zn alloys.

Highlights

The main reason of the limited usage of wrought magnesium alloys in structural applications is their low ductility and poor formability that produce higher costs and difficulties in their forming processes [1,2]
The aim of the present work was to investigate the effect of the shear deformation introduced by differential speed rolling (DSR) processing on the microstructure, texture and mechanical properties of
The level of introduced shear stresses during DSR was controlled by adjusting different speed ratio (R) between upper and lower rolls, i.e., R = 1, 1.25, 2 and 3

Summary

Introduction

The main reason of the limited usage of wrought magnesium alloys in structural applications is their low ductility and poor formability that produce higher costs and difficulties in their forming processes [1,2]. Mg alloys with the low symmetry hexagonal close-packed structure show limited formability due to unsatisfactory number of independent slip systems. At room temperature dislocation slip in Mg occurs mainly on the densely packed basal (0001) planes along the directions. One of the approaches to increase formability of Mg is the use of alloying elements, which decrease stacking fault energy (SFE) of Mg [5,6,7]. Muzyk et al [8] has proven by the density functional theory (DFT) that the so-called generalized stacking fault energy (GSFE)

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Conclusion