Microstructure and properties of C70250 copper alloy during continuous extrusion-cold rolling-aging process
In this paper,C70250 alloy rod with diameter of 25 mm was used as raw material,and the 320 mm× 14 mm large-width U-shaped continuous extrusion slab and the subsequent cold rolling and aging process of the alloy were studied,aiming to explore a new short-process preparation technology for high-strength and high-conductivity copper alloy. Firstly,the finite element simulation method was used to analyze the key field quantities of C70250 alloy in the continuous extrusion process,and then the experimental study was carried out. The optical microscopy (OM),scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to analyze the microstructure of the alloy samples,and the performance tests were carried out by the microhardness tester,universal testing machine and conductivity measuring instrument. The results show that the grain is significantly refined and homogenized after continuous extrusion,a small amount of Ni2Si phase is precipitated in the matrix,the conductivity decreases from 37.47％IACS to 30.27％IACS,and the hardness increases from 88.0HV to 108.9 HV. The grain size of the slab gradually decreases from the edge to the core in the transverse direction,the hardness gradually increases,the microstructure and hardness are evenly distributed along the extrusion direction,and the grain size gradually increases from the surface to the core in the thickness direction,and its hardness core is low at the center and high at the position and near the upper and lower surface. The fiber structure of strip after cold-rolled is formed and accompanied by grain fragmentation,and the comprehensive performance of the alloy strip is greatly improved after aging treatment. The alloy strip prepared by the U-shaped continuous extruded slab is treated by cold rolling with deformation 87.5％-(450 ℃,1 h) pre-aging+cold rolling with deformation 66.7％-(350 ℃,2 h) aging,the hardness reaches 233.8HV,the conductivity reaches 47.82％IACS,the tensile strength is 688.0 MPa,and the elongation is 10.2％.
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