Continuous Extrusion Process Simulation And Stress Relaxation Optimization Of Cu-0.23Cr-0.08Ag Alloy

In order to solve the contradictory technical problem of high alloy strength and low die life in the continuous extrusion process of high performance copper alloy,it is necessary to conduct in-depth study on the continuous extrusion process of copper alloy,and determine appropriate process parameters and die materials according to its deformation law and microstructure evolution characteristics.High temperature stress relaxation is one of the most important mechanical properties of Cu-Cr-Ag alloy,but there are few reports about this property and the mechanism is not clear.Therefore,in this paper,based on the hot compression experiment,the deformation law and microstructure evolution of Cu-0.23Cr-0.08Ag alloy during continuous extrusion were studied by Deform-3D software.The samples were cold rolling after continuous extrusion,and the influences of different cold rolling deformations on the microstructure,grain boundary characteristics and mechanical properties of Cu-0.23Cr-0.08Ag alloy were studied.The relationship between the low ?CSL grain boundary and stress relaxation resistance of Cu-0.23Cr-0.08Ag alloy were also studied.The results show that:(1)The more accurate constitutive model of Cu-0.23Cr-0.08Ag alloy after friction correction is as follows:?=3.96 × 1015[sinh(0.01815?)]6.82135exp(-342536.12/RT)The numerical simulation results of Cu-0.23Cr-0.08Ag alloy under different deformation conditions show that 750? and 7r/min are the best continuous extrusion process parameters.In this process,the difference between the microstructure simulation results and the actual microstructure of the alloy is very small,which shows that the numerical simulation model of continuous extrusion is accurate and reliable.In addition,the continuous extrusion process can greatly refine the grains and improve the mechanical properties of Cu-0.23Cr-0.08Ag alloy.(2)With the increase of cold rolling reduction,the grain size of Cu-0.23Cr-0.08Ag alloy first increases and then decreases,and then increases again when the deformation is 60%.The influence of cold rolling deformation on grain boundary characteristics is particularly obvious,only the appropriate deformation(10%)and annealing treatment can greatly increase the percentage of low ?CSL grain boundaries,reaching 60%.With the increase of deformation reduction,the hardness and tensile strength of the alloy increase,however,the conductivity of the alloy decreases.When the deformation reduction is 60%,the conductivity of the alloy increases.(3)The stress relaxation results of Cu-0.23Cr-0.08Ag alloy show that the alloy with the deformation of 10%and the highest the percentage of low ?CSL grain boundary has the best property of stress relaxation.After stress relaxation,the grain size and the percentage of low?CSL grain boundary of the alloy with the deformation of 10%did not change significantly,while the grain size and the percentage of low ?CSL grain boundary of the other alloys with different deformations decreased,however,the hardness and conductivity of the later increased.There are two main factors affecting the stress relaxation properties of the alloy:one is the pinning of Cr relative movable dislocation,the other is the obstruction of twins to the movement of movable dislocation.High percentage of low ?CSL grain boundary is helpful to improve the stress relaxation resistance of the alloy when the other conditions are certain.