Effects of broken β-Mg17Al12 and non-uniform Mg2Pb particles introduced by EX-ECAP on microstructure and mechanical properties of Mg–Pb-9.2Al-0.8B alloys

Abstract

Mg–Pb-9.2Al-0.8B alloy faces a significant strength-toughness balance problem in applications. To address this challenge, severe plastic deformation was applied to the alloy by combining traditional extrusion with multi-pass equal channel angular pressing (EX-ECAP). The research delves into the microstructural evolution (including broken β-Mg17Al12 and non-uniform Mg2Pb particles) and its effects on the strengthening mechanisms. The synergistic effects of grain boundary strengthening due to grain refinement, Orowan strengthening, geometrically necessary dislocation strengthening, and coefficient of thermal expansion strengthening collectively enhance the tensile strength and ductility, balancing the strength and toughness. The results showed an impressive ultimate tensile strength of 386.1 MPa, which is 2.33 times that of the as-cast alloy. The altered fracture morphology clearly indicated a transformation from brittle to brittle-ductile fracture mode. During the deformation process, the activation of dislocations, atomic-scale ripples, minor lattice distortions, and kink bands enhance the macroscopic flexibility. The introduction of EX-ECAP presents new opportunities for manufacturing high-performance Mg–Pb-9.2Al-0.8B alloy through integrated deformation techniques.

Keywords

• Magnesium alloy
• Mechanical properties
• EX-ECAP
• Microstructure