Diffusion And Bonding Strength Of AZ91/Al Composite Fabricated By Brazing

Magnesium and magnesium alloys have a lot of outstanding characteristics ontechnology and performance, which have been widely used in the electronics,communications, automotive and aviation industries. However the corrosion of magnesiumand magnesium alloy is one of the main problems and it has greatly limited magnesiumalloy widely used in the fields of engineering in a long time, making its performance notplay excellently. To the purpose of the anti-corrosion, a plate of AZ91magnesium alloyswas linked to a1mm thick plate of layer Al. After brazing and hot-rolling orhot-compressing, AZ91/Al composites can successfully be achieved.The study found that the method of brazing and hot-rolling at390℃can successfullyfabricate AZ91/Al composites. Then the AZ91/Al composites were annealed by4h/8h as adiffusion treatment. The mechanical properties the AZ91/Al composites fabricated bybrazing and hot-rolling without annealing treatment is biggest and can reach22.46MPa. Asthe annealing time increased, the diffusion region of the interface was continuously gettingwider, forming more and more MgZn₂and Mg₂Sn inter-metallic compounds. At last, all Znand Sn solder at the interface translated into compounds. At the same time, as timeincreased, the performance of shear fracture of AZ91/Al composites is brittle moreobviously. In this case, the diffusion annealing treatment can not significantly increase thebonding strength. The main reason of the fracture was the presence of MgZn₂and Mg₂Sncompounds.At350/370℃, brazing and hot-compressing method also can successfully fabricateAZ91/Al composites. AZ91/Al composites fabricated by brazing and hot-compressing at350℃,40MPa for30min can obtain the maximum mechanical performance,reaching35.64MPa. As time increased, the diffusion region of the interface was continuouslygetting wider. Then the amount of MgZn₂compounds that formed in the interface of thediffusion region was continuously more. Finally Mg₂Zn11inter-metallic compoundsgenerated at the interface. As time increased, it can be found that the shear fracture of AZ91/Al composites was brittle more obviously and the more the apparent cleavage stepscame out. In this case, the diffusion annealing treatment can not play the role in increasingbonding strength.