Khokhlov M. Features of the formation of a bimetallic compounds of porous aluminum alloys and monolithic magnesium alloys.

The work is devoted to the determination of the optimal method for obtaining a bimetallic material from monolithic magnesium alloys of the Mg-Al-Zn system and porous aluminum of the Al-Mg-Zn system. The influence of gallium activation under various welding conditions on the microstructure, chemical and phase composition and mechanical properties of the diffusion zone of the compounds was studied. It was found that diffusion welding of porous aluminum with monolithic magnesium alloys, under vacuum conditions with a velocity V=5°C/min and without evacuation with a velocity V=100°C/min forms diffusion zones with a total width of ~300 μm and ~70 μm with the same chemical composition and properties. In magnesium alloy, diffusion zone width is 85...100 μm and 50...60 μm, respectively, in which the intermetallic compound Mg5Ga2 is formed. The diffusion of gallium into aluminum alloys leads to decrease in the microhardness of the contact zone from 1,3 GPa to 0,8 GPa and Young's modulus from 70 GPa to 36 GPa, and into magnesium alloys – leads to increase in the microhardness of the contact zone from 1,2 GPa to 3 GPa, Young’s modulus from 42 GPa to 73 GPa. The computer simulation method shows how the diffusion zone of magnesium alloy is strengthened by the formation of Mg5Ga2 intermetallic phase and by the boundaries between the hexagonal lattice of magnesium and the orthorhombic lattice of the Mg5Ga2 phase. The optimal welding mode was determined – temperature 300°C, pressure 5 MPa, duration 5 min, current density 0,8 A/mm2. The shear strength of the obtained bimetal material samples is 25,8...26,5 MPa, which is satisfactory for compounds of this type.