Structures and Hardness of Materials Formed by Melting and Liquid Diffusion of Mg Alloy Substrate with Pure Al Surface

Abstract

In this study, pure Al powder was compression molded on the surface of flame-retardant Mg alloy plate, and integration of pure Al and Mg alloy was attempted by melting and solidification in air. In order to integrate different materials by liquid diffusion of metal elements, the structure, composition phase and hardness of the formed integrated materials were investigated.

It was found that heating the specimens for 180 s results in melting and liquid diffusion between Al and Mg. When heated and melted with pure Al down and Mg alloy up (Type B), shrinkage cavity was formed on the former Mg alloy side of the former Al/former Mg alloy interface. When heated at 450 s, the specimen was composed of Al–Mg system stable phases of Al₃Mg₂ and Al₁₂Mg₁₇, and Al–Mg system metastable phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9. In Type A with pure Al up and Mg alloy down and Type B, stable phases of Al₃Mg₂ and Al₁₂Mg₁₇ were formed on the former Al side. The constituent phase of the former Mg alloy side was composed of metastable phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9, but the structure morphologies of Type A and B differed near the surface of the former Mg alloy side, and the primary phase was Al_0.37Mg_0.63 and Al_0.1Mg_0.9 respectively. The final solidification phase consisted of eutectic phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9. The hardness on the former Al side was about 250 HV, and the hardness on the former Mg alloy side had decreased. Type B was evaluated to be lower than Type A.

 

This Paper was Originally Published in Japanese in J. JFS 92 (2020) 69–74.