Study of microstructure evolution in the aluminum‒magnesium alloy AlMg6 after explosive welding and heat treatment

Aluminum‒magnesium alloys are widely used in the shipbuilding and railcar industries because of their high specific strength and corrosion resistance. However, the welding of aluminum–magnesium alloys to steel poses a number of significant issues, mainly due to the formation of brittle intermetallic compounds (IMCs) and adiabatic shear bands (ASBs). The effects of IMCs on the mechanical properties of joints have been well researched, but there is a limited understanding of how ASBs and magnesium affect these properties. In this work, the effects of ASBs and Mg₂Al₃ on the mechanical properties of explosive-welded bimetals are studied. Optical microscopy, electron microscopy, confocal laser scanning microscopy, and electron backscatter diffraction (EBSD) were performed. Additionally, Vickers hardness tests, tear strength tests, and bending tests were carried out to determine the mechanical properties of the specimens. The results of the study revealed that at the weld interface after explosive welding, a zone of fine dark-etching Mg₂Al₃ phase accumulation up to 10 µm thick and an ASB zone up to 400 µm thick formed. The thickness and included volume of both zones increase from 3 to 20 vol.% with increasing detonation velocity. The tear strength also increases (from 80 to 230 MPa). After heat treatment at 200 °C for 1 h, the specimens survived at twice the bending angle, indicating good plastic properties. Thus, the results help elucidate the influence of Mg₂Al₃ and ASBs on the properties of bimetals with AlMg6 alloys obtained via explosive welding.