Mechanical behaviour of AZ31 magnesium alloy with the laminate and gradient structure

ABSTRACT

A laminate and gradient structured (LGS) AZ31 magnesium alloy was produced via a combination of surface mechanical attrition treatment (SMAT) and accumulative roll-bonding (ARB) in an attempt to improve the AZ31 strength-ductility relationship. The effects of the rolling temperature and number of passes on the microstructure and mechanical properties were researched. The LGS AZ31 Mg alloy microstructure included periodic distributions of fine grain (FG) layers, coarse grain (CG) layers, and FG layers in which the grain size exhibited a gradient transition. A depth-dependent gradient microhardness was generated because of the corresponding gradient microstructure. The effect of the LGS AZ31 Mg alloy on grain size-dependent strengthening mechanisms was researched. The yield and ultimate tensile strengths of the alloy improved dramatically and there was a slight decrease in the fracture elongation. The tensile properties of the sample present good strength-ductility relationships. This is attributed to LGS. The microstructure could change the crack propagation path and enhance alloy strength without much harm to plasticity. The overall influences of SMAT and ARB on mechanical properties, which include dynamic recrystallisation, dislocation activity, and the influences of interfaces, were researched. To illuminate the differences in the deformation behaviours of FG and CG layer microstructures, tensile test samples were imaged via SEM.

KEYWORDS:

• Magnesium alloy
• laminate and gradient structure
• surface mechanical attrition treatment
• accumulative roll-bonding
• microstructure
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Basic Research Program of China [Nos. 2017YFB1103701, 2016YFB0701201, 2016YFB0701203], the Natural Science Foundation of China [Nos. 51671101, 51761037], Natural Science foundation of Jiangxi Province [Nos. 20172BCB22002, 20171BCD40003, 20161BAB206128], the Innovative Funding for Graduate Students in Nanchang University [No. CX2017062].