Superplastic Forming/reaction Diffusion Bonding Process Of Honey Comb Structure For Mg-Gd-Y-Zn-Zr Rare Earth Magnesium Alloy

The superplastic forming/diffusion bonding combined process technology is a lightweight forming technology developed in the 1970 s.It has the characteristics of low cost,high efficiency,and almost no margin.The formed parts have good integrity,accurate size,There is no obvious weld seam and the material properties of the welded part are consistent with the performance of the base material.At present,SPF / DB components have gradually developed into complex multilayer components.The use of SPF / DB components can reduce weight compared with the use of traditional steel structures by 20% ? 40%,reduce manufacturing cost by 20% ? 50%.Among them,the most widely used materials are titanium alloys and aluminum alloys,but they are rarely used in magnesium alloys.Magnesium alloys are extremely lively and easily oxidized to form a dense oxide film when exposed to air,which greatly affects the diffusion of magnesium alloys‘ connection.In response to this problem,this topic adopts the method of introducing copper as the intermediate layer to improve the strength of the diffusion connection.During the diffusion connection,the intermediate layer and the magnesium alloy undergo a solid phase reaction to form a new phase to complete the solid phase bonding?reaction diffusion bonding,RDB?.This method not only perfectly solves the problem of oxide film,but also the reactive diffusion connection can be carried out under a small pressure?2 ? 4MPa?,reducing the need for forming equipment and damage to the mold,which greatly saves costs.In this paper,with the development of Mg-Gd-Y-Zn-Zr alloy multilayer structure as the background,the superplastic forming/reactive diffusion bonding?SPF/RDB?process test was studied.The unidirectional high temperature tensile test of Mg-Gd-Y-Zn-Zr alloy was carried out under different deformation temperature and strain rate conditions.The influence of each parameter on flow stress,strain and elongation rate of the alloy was analyzed.It was determined that the optimal deformation temperature of Mg-Gd-Y-Zn-Zr alloy was 475 ?,strain rate was 0.0005s^-1,and elongation rate was about 420%.According to the stress-strain curve of the alloy under different deformation parameters,the K value and value was obtained.According to the principle of orthogonal design,the diffusion bonding properties of Mg-Gd-Y-Zn-Zr alloy were studied.The effects of bonding temperature and interface roughness parameters on the quality of diffusion bonding joint were analyzed.The results show that the diffusion joint has the best quality under the condition of 460 ?,30 min of holding time and 2MPa of pressure,and the roughness of the interface has little effect on the quality of the joint.The shear strength of the joint under the condition of the best diffusion parameters is 152 MPa,which is 98.7% of the base metal.According to the material parameters obtained from high-temperature tensile test,msc.marc2018 is used to simulate the forming of hollow double-layer structure,three-layer structure and four layer curved honeycomb structure.According to the simulated air pressure loading curve,the air pressure loading of superplastic forming in SPF / RDB process is guided.According to the results of basic performance test and finite element simulation of sheet metal,the forming die and corresponding air pressure control system are designed,the technological process is formulated,the SPF / RDB test is carried out with the best forming technological parameters,the final formed part is obtained,and the wall thickness of the formed part is measured and analyzed.It is found that the error between the wall thickness of the formed part and the simulation result is small,and the structure of the diffusion joint of the formed part is observed.The connection interface disappears,and some fine Mg₂Cu phases are distributed at the boundary of diffusion transition zone,and the diffusion connection joint is well connected.