Influence of strain, temperature, and strain rate on interfacial structure and strength of AZ31BMg/6063Al formed by plastic deformation bonding

Abstract

Strain, and temperature, and strain rate, are critical parameters in many joining and forming processes of Al/Mg alloys hybrid structures/components, but the relation between those parameters and interfacial bonding strength remains to be quantified. In the present study, influences of true strain (0.29−0.92), strain rate (10−3-10 s-1), and temperature (325–443 ℃) on microstructure and interfacial bonding strength of AZ31BMg/6063Al formed via plastic deformation were studied, and mechanism-based constitutive equations describing the relation between those parameters and interfacial bonding strength were first developed. Mg and Al alloys cannot be bonded at true strains 0.29 and 0.51 lower than theoretical threshold true strains; while metallurgical bonding appears at Al/Mg interfaces as the true strain is increased to 0.92. When the bonding interface is not fully bonded, a decreased strain rate or an increased temperature helps to improve the metallurgical bonding area, resulting in the enhancement of bonding strength. However, once the bonding interface has been fully bonded, a decrease in strain rate or an increase in temperature leads to an increase in intermetallic compounds (IMCs) thickness, thus almost linearly reducing bonding strength. The IMCs thickness has an exponential relation with time and an Arrhenius relation with temperature. The interfacial bonding strength is governed by both the bonding degree and IMCs thickness. The combination of a large strain rate and a high temperature (below constitutional liquation) helps to form a fully bonded interface with a small IMCs thickness, thus obtaining the maximum bonding strength. The present research findings and developed models provide guidance for parameters optimization in joining or forming processes of Al/Mg alloys hybrid components via plastic deformation.