Ductility Improvement of an AZ61 Magnesium Alloy through Two-Pass Submerged Friction Stir Processing

Xicai Luo; Genghua Cao; Wen Zhang; Cheng Qiu; Datong Zhang

doi:10.3390/ma10030253

Ductility Improvement of an AZ61 Magnesium Alloy through Two-Pass Submerged Friction Stir Processing

Materials (Basel). 2017 Mar 2;10(3):253. doi: 10.3390/ma10030253.

Authors

Xicai Luo¹, Genghua Cao², Wen Zhang³, Cheng Qiu⁴, Datong Zhang⁵

Affiliations

¹ National Engineering Research Center of Near-net shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, China. meluoxicai@mail.scut.edu.cn.
² Guangdong Key Laboratory for Advanced Metallic Materials Processing, South China University of Technology, Guangzhou 510640, China. cghcaogenghua@126.com.
³ National Engineering Research Center of Near-net shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, China. jack_eei@scut.edu.cn.
⁴ National Engineering Research Center of Near-net shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, China. cqiu@scut.edu.cn.
⁵ National Engineering Research Center of Near-net shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, China. dtzhang@scut.edu.cn.

Abstract

Friction stir processing (FSP) has been considered as a novel technique to refine the grain size and homogenize the microstructure of metallic materials. In this study, two-pass FSP was conducted under water to enhance the cooling rate during processing, and an AZ61 magnesium alloy with fine-grained and homogeneous microstructure was prepared through this method. Compared to the as-cast material, one-pass FSP resulted in grain refinement and the β-Mg₁₇Al₁₂ phase was broken into small particles. Using a smaller stirring tool and an overlapping ratio of 100%, a finer and more uniform microstructure with an average grain size of 4.6 μm was obtained through two-pass FSP. The two-pass FSP resulted in a significant improvement in elongation of 37.2% ± 4.3%, but a slight decrease in strength compared with one-pass FSP alloy. Besides the microstructure refinement, the texture evolution in the stir zone is also considered responsible for the ductility improvement.

Keywords: AZ61 magnesium alloys; friction stir processing; mechanical property; microstructure; texture.