Mechanical behavior of a Mg/Al composite rod containing a soft Mg sleeve and an ultra hard Al core

Abstract

In the present study, microstructure and mechanical behavior of a Mg/Al composite rod with a soft Mg AZ31 sleeve and an ultra hard Al 7050 core were systematically studied, with the aim to disclose the influence of Al core on microstructure and texture of Mg sleeve and that of Al fraction on mechanical behavior. Our results show that, compared to extrusion of a monolithic Mg billet, co-extrusion of the Mg/Al bimetal billets does not change the typical extrusion texture of Mg sleeve, but can effectively refine the grains in Mg sleeve. The Mg/Al composite has much higher tensile or compressive yield strengths than the monolithic Mg rod, meanwhile a similar plasticity. With the Al fraction up to 33.8%, the tensile yield strength increases by about 61% and compressive yield strength by about 214%. The Mg/Al rod also possesses a much lower tension-compression yield asymmetry than the monolithic Mg rod. A higher Al fraction further reduces this yield asymmetry. Both the inclusion of a hard Al core and the grain refinement in Mg sleeve contribute to the quite high strength and the much lower yield asymmetry in Mg/Al rod. The Al fraction hardly affects {101¯2} twinning activity in Mg sleeve.