Study On Diffusion Bonding Of AZ31 Magnesium Alloy

With the fast development of industrial technology, people will be higher property requirements for automobile and aeroplane. Reduing strcture weight is the most important method to improve its performance. Magnesium alloy is the lighest one of metal structural materials. Its density is small, its dimension is stable. And magnesium alloy have a good characterized in electromagnetic shielding, thermal conductivity and recoverability. it is widely used in the fields of aerospace, automobile, telecommunications and electronic industry. Due to diffusion bonding has many special characteristics campared with fusion welding and brazing. Consequently, it causes people's attention and becomes hot topic in research field recently.Diffusion bonding of AZ31 magnesium alloy was approved by experiment in this paper. Optimal craft parameter was confirmed:temperature-450 degree, bonding time-60min, bonding stress-15MPa. Micrograph in bonding field were analysed depending on metallurgical microscope and microhardness testing machine and so on. The result showed that crystall is refined and structrue is compacted. The microhardness was increased for workhardening and recrystallization in welding process. And Equivalent compressive strain was anaslysed in diffusion bonding, the result showed that stress increases with the temperature increasing. This is mainly due to lineal inflated coefficient increased with temperature increasing.Grain size was refined by ecrystallization, according to theory of ecrystallization anneal, the result shows that grain size was changed from 34μm to 13μm for 60 minutes in 200 degrees. Compared with original sample, refined sample can decrease bonding time, because effective diffusion coefficient annealed is larger than effective diffusion coefficient of original sample in the same situation.The most microhardness was tested in bonding surface by microhardness tester. With variety of distance, microhardness decreases and microhardness is constant.The grain is finer by recrystallization reorganization, and the micro-plastic deformation is produced in regional welding organizations. Shear strength increased with temperature increasing by shear experiment in universal tester, meanwhile, it was apprived that original grain size is smaller, the time is shorter to obtain the same shear strength in diffusion bonding. This experiment supplies reference for research of superplastic diffusion bonding.