Research On Preparation Of Cu-Cr-Zr Alloy Based On Vacuum Horizontal Continuous Casting And The Microstructure Evolution And Property Regulation Of Its Wire

With the increasing performance requirements of aerospace and high-end electronic information equipment for electronic components,wire and cable for the transmission of power and signals for electronic components are also developing in the direction of higher strength,higher conductivity,lighter weight and higher reliability.Its extreme use environment determines the strict requirements for various properties index of high-strength and high-conductivity cables and their conductors.Cu-Cr-Zr alloys have the potential to be developed into high performance copper alloy conductor materials for the aerospace and high-end electronic information industries due to their excellent strength,electrical conductivity and resistance to softening.However,there are still more problems with the preparation of Cu-Cr-Zr alloy ingots and the processing of their wire in China,including the fact that continuous billet production technology with stable composition and good surface quality has not yet been achieved.And how to get balance the relationship between strength and conductivity through thermomechanical treatment process to achieve the goal of developing"double 70"high-performance copper alloy（tensile strength≥700 MPa,conductivity≥70%IACS）.In order to solve the above problems,the following research was carried out in this topic:1.A method of vacuum horizontal continuous casting was proposed to prepare Cu-Cr-Zr alloy casting billet.The innovative use of a combined boron nitride and beryllium copper crystalliser has resulted in a significant improvement in the surface quality of vacuum horizontal continuous casting of Cu-Cr-Zr alloys by redesigning and improving the structure of the crystalliser.At the same time,the simulation of the temperature field,solid-liquid interface shape and solidification microstructures of vacuum horizontal continuous casting using Pro CAST software,optimised the casting parameters of vacuum horizontal continuous casting,and clarified the factors affecting the quality of vacuum horizontal continuous casting Cu-Cr-Zr alloy billets.The optimum vacuum horizontal continuous casting process was obtained by a combination of solidification simulation and experimentation,where the casting temperature was 1100°C and the traction speed was 5 mm/s.2.Vacuum horizontal continuous casting was carried out using optimised casting parameters to continuously obtain Cu-0.8Cr-0.1Zr alloys with uniform composition and excellent surface quality.The multi-stage thermomechanical treatment process was applied to the vacuum horizontal continuous casting Cu-0.8Cr-0.1Zr alloy,and through the regulation of the microstructure and properties,a combination of properties with a tensile strength of 803MPa and an electrical conductivity of 76%IACS was achieved.The excellent strength and electrical conductivity was mainly attributed to the genetic properties of the Cr-rich phase and its interaction with nanostructures（nano-layered structure and substructures）with high temperature stability.3.The microstructure evolution and deformation mechanism during the preparation of vacuum horizontal continuous casting Cu-0.8Cr-0.1Zr alloy wire was systematically analysed.In particular,an innovative in depth analysis of the differences in grain boundaries,recrystallization organization,fiber structure,local strain and dislocation density in the deformation zone of drawn and solid solution samples with different deformations（ε=23.4%～34.0%andε=34.0%～43.8%）has been carried out.The growth mechanism of twins and the deformation mechanism of Cr-rich phases of different morphologies were also discussed.It showed that Cu-0.8Cr-0.1Zr alloy wire has finer grains in the surface layer of the reducer zone,more dense distribution of small-angle grain boundaries,larger local stress changes,higher dislocation density,and more prone to recrystallization,which was mainly twinning.The large deformation and the large stress around the Cr-rich phase promoted the（111）_Cu twin plane to move and form a 70°mirror symmetry withΣ3 twin.And the texture was rearranged after solution treatment,the proportion was in accordance with<100>∶<110>∶<111>≈2∶2∶1.The fusiform Cr-rich phase was produced when the deformation of the as-cast spherical Cr-rich phase was just started.If the deformation was increased,it will be drawn into a long strip.4.The practical application properties of Cu-0.8Cr-0.1Zr alloy wire（1 mm）in terms of tensile,torsional,softening resistance and nickel plating were comprehensively analysed for the use scenarios of Cu-Cr-Zr alloy wire and evaluated according to national standards.The reduction of area of Cu-0.8Cr-0.1Zr alloy wire was up to 70%,which can provide a good blank for the preparation of alloy ultra-fine wire.Its torsional properties meet the requirements of the current national standards.The softening temperature characteristic curve of wire rod conforms to the Logistic regression model,and the softening temperature was about 547℃.The nickel content of the electrodeposited coating of wire rod can reached grade 7,and electroless nickel plating can form a co-deposited coating of Zr and Ni,which may have a beneficial impact on the subsequent processing performance of wire rod.