Research On The Microstructure And Properties Of High-Strength And High-Conductivity Copper Silver Alloy Prepared By Horizontal Ohno Continuous Casting

China is a most country of copper production and consumer in the world.In 2019,the domestic output of copper processing products reached 18.16 million tons,ranking first in the world for 16 consecutive years.Among them,there were 8.16 million tons of copper wire.It is widely used in power equipment,electronic information and other fields.With the arrival of 5th-Generation times,the high performance copper silver alloy wire diameter and better structural stability.Therefore,higher requirements are put forward for continuous ultra-fine forming ability,high strength and high conductivity of wire rod.At present,the copper alloy wire used in the high-end field is mainly imported from Japan and other countries.So,how to improve the existing technology to obtain the continuous preparation technology of copper silver alloy wire with good as cast structure.And,based on the contradictory relationship between the electrical conductivity and mechanical properties of copper alloy,how to control the comprehensive properties of Cu-Ag alloy through the combination and cooperation of various processes.They are of great significance to the development of high-end copper alloy materials in the key national field of "bottlenecks".In this paper,the as cast Cu-3.5Ag alloy was prepared by horizontal Ohno continuous casting process.The influence of continuous casting speed(20,30,40,50,60 mm/min)on the as cast structure and properties of the alloy was studied.Through the heat treatment of single solution(950 ?×1 h)+ aging(450 ?,holding for 2,4,6,8 h),the effect of aging time on the electrical conductivity,hardness and precipitation characteristics of nano strengthening phase was studied.On this basis,the effects of solution + aging + drawing,solution + drawing + aging on the electrical conductivity and strength of Cu-3.5Ag alloy were studied by means of solution,cold deformation(drawing)and aging.The evolution law of the characteristic parameters of precipitates in different processes was studied by means of transmission electron microscopy(TEM).The results show that:1.In the test range,when the continuous casting speed is 50 mm/min,the strength and electrical conductivity of Cu-3.5Ag alloy are 206.5 MPa and 85.6 %IACS,respectively.The comprehensive properties are better than other continuous casting speeds.The continuous casting speed has a significant effect on the microstructure,strength and electrical conductivity of Cu-3.5Ag alloy.The microstructure perpendicular to the direction of continuous casting is dominated by interlaced "wovenfabric" dendric morphology,And,the number and size of "wovenfabric" dendrites are related to the change of strength.The microstructure parallel to the continuous casting direction is dominated by regular arrangement of "fishbone" dendrites.And,the change of electrical conductivity is mainly related to the number and distribution of "fishbone" dendric morphology.In addition,the non-equilibrium eutectic phase is mainly distributed in the dendrite arm spacing.2.After solution 950 ?×1 h + aging 450 ? for 4 h,the hardness and electrical conductivity of Cu-3.5Ag alloy are 122.62 HV and 86.20 %IACS,respectively.With the increase of aging time,the hardness was increased sharply at first,then was decreased slowly and finally became flat.The electrical conductivity was increased rapidly at first,and then became stable,which was not sensitive to aging time(the fluctuation range was1 %IACS).The aging time has a significant effect on the morphology,size,quantity of precipitates,the interface relationship and the orientation relationship between rich-Ag phase and matrix.When the aging for 4 h,a large number of rich-Ag phases are chain precipitated with the average diameter of 17-19 nm,and there are crystal defects and a large number of dislocations around.Most of the rich-Ag phases are spheroidal,and a small number of short rods are formed by close arrangement of spheroids.3.Cold deformation is introduced on the basis of solution and aging,and it has different effects on the conductivity and mechanical properties of Cu-3.5Ag alloy before and after aging.After solution,aging and drawing,the average diameter of rich-Ag phase in Cu-3.5Ag alloy is 12-14 nm.After drawing,the size of rich-Ag phases is decreased,and drawing was beneficial to dislocation entanglement and dislocation accumulation,forming dislocation substructure.The mechanical properties of Cu-3.5Ag alloy is significantly improved(the strength and electrical conductivity of Cu-3.5Ag alloy are 417.2 MPa and 84.7 %IACS,respectively).And,the strengthening mechanism of this process is to give full play to the synergistic strengthening effect of aging precipitation strengthening and deformation strengthening.After solution,drawing and aging,the conductivity of Cu-3.5Ag alloy reached 95.5 %IACS,while the strength of Cu-3.5Ag alloy increased slightly(247.5 MPa).The precipitates are a short rod rich-Ag phase with an average width of 32-35 nm,and it tends to nucleate at the dislocation.This process,the precipitation efficiency and precipitation rate are promoted by applying cold deformation before aging(thermomechanical treatment),the lattice distortion caused by solid solution is greatly reduced,and the conductivity is improved.4.On the basis of the above research,the influence of solution(950 ?×1 h)+ multi pass continuous drawing process(? 16 ?? 12.5 ?? 11 ?? 10 ?? 9 ?? 7.9 ?? 6.8?? 6 ?? 4 ?? 2 ?? 1.5 mm,without intermediate annealing)on the strength and conductivity of Cu-3.5Ag alloy was studied.It is found that the tensile strength of the alloy is 530.5 MPa and the conductivity is 82.29 %IACS,when it is continuously drawn to ? 2 mm.The comprehensive performance index of the alloy is higher than that of the same kind of imported Cu-(3-4)Ag alloy from Japan,and the micro mechanism of the improvement of the comprehensive performance needs to be further studied.