Study On Extrusion Shear Preparation Technology And Microstructure Properties Of AZ31B/AA6063 Composite Rod

Based on the DEFORM-3D finite element numerical simulation software,the forming process of AA6063/AZ31B bimetallic composite rod by way of extrusion and shearing was simulated.To begin with,several factors were analyzed,including the mesh change,temperature field distribution,stress and strain,the technical parameters on load,as well as the temperature field distribution during the forming process.And the optimum technological parameters based on the theory were eventually determined by virtue of orthogonal Test Method.Finally,the composite bar made by physical extrusion experiment,combined with the advanced Characterization of material structure and properties,were tested and analyzed in terms of the interfacial bonding layer morphology,microstructure texture and mechanical properties(microhardness,bonding strength).The final conclusion are as follows.Under relevant numerical simulation,it was found that there are some factors,namely,the grid change,temperature field distribution,stress-strain distribution of the semifinished billet,are mainly affected by the die structure.In addition,the deformation of the outer material lags relatively behind that of the inner magnesium alloy.According to the Orthogonal Test Method,the effects of different extrusion temperature,extrusion speed and friction-factors on forming load were analyzed to determine the optimum technological parameters.The final order of their impacts is as follows:extrusion temperature>friction-factors>extrusion speed.Hence the theoretically optimal extrusion process parameters is:extrusion temperature 390?,extrusion speed 1 mm/s,friction factor 0.1;By analyzing the parts of the preparation of physical experiment found that the front-end parts of sample appear obvious stratification phenomenon,namely the inner magnesium alloy extrusion process will be part of extrusion parts based on section observation found that common extrusion parts combining layer exists obvious gap,and parts of the preparation of extrusion shear section has no obvious gap and uneven distribution of stamping outer cladding material thickness.By analyzing SEM and EDS,the results show that the temperature has a promoting effect on the composite of the two materials during the same forming process;while the extrusion shear process is better than the common extrusion process for the manufacture of bimetal composite bar.In this research,the optimal interface bonding layer is the micro zone of composite bar interface bonding layer made by extrusion-shear process at 390?,whose thickness and the stable layer is about 32?m and 15?m respectively.Besides,the micro zone thickness of each part increases with the temperature.Meanwhile,the stable layer is not found in the composite bar produced by common extrusion,and the thickness of the micro zone is irregular.Under the two different techniques,the figure near the magnesium side is Al₁₂Mg₁₇while that near the aluminum side is Al₃Mg₂.This paper also studied the organizational evolution of products in different regions at the basis of extrusion-shear process.It shows that the billet posses better stress condition along the extrusion direction during the forming process.And it is difficult for aluminum alloy to recrystallize during extrusion.Therefore,the recrystallization region of the formed parts is lower than that of magnesium alloy.Moreover,the characteristic texture of aluminum alloy changes before and after forming and extrusion shear forming can improve the plasticity and toughness of magnesium alloy.Through the analysis and measurement of the composite rod microhardness during the extrusion and shearing process,it is found that the microhardness near the magnesium side is about 65 HV and the hardness of combination area is about 221 HV while the hardness at aluminum side is 92 HV or so.Through the push out test,the study has found that the bonding strength of composite bars and its characteristics in different areas are distinct,of which the maximum shear strength is 36.32MPa and the minimum is 11.01MPa.