Preparation And Study On Properties And Structure Of Cu-X/(Zr-X)(Sn、Ag、In、 Sb、Sn+In) Microalloy

Copper has excellent physical and chemical properties like noble metals. Especially its good plasticity and conductivity inferior slightly to silver make it used widely in electrical industry. A large number of copper is used to produce electrical equipments, such as generator, cable, transformer, switchgear, and so on. But thanks to the strength of the pure copper is low and work hardening copper is easy to soften, the application of copper is limited severely. By adding trace Sn、Ag、In、Sb and Zr elements making copper micro alloying, this paper would study the influence of the different elements and treatment process to the performance and microstructure of microalloys, through which we hoped to improve the strength and heat resistance of copper alloy.This paper used two kinds of copper with different purity(The purity of Cu I and Cu Ⅱ are 99.95% and 99.99% respectively), and prepared a variety of microalloys of Cu-X/(Zr-X)(Sn、Ag、In、Sb、Sn+In) by vacuum induction melting and electric arc melting. By metallographic microstructure observation、fracture morphology observation、electrical conductivity test、microhardness test and tensile performance test, the conductivity, mechanical properties and microstructure of microalloys cold-worked and heat-treated were tested and analyzed. The research shows that:(1)For the pure Cu I, The solid solution strengthening effect to microalloys after solid solution treatment and cold working of the trace Sn、Ag、In and Sb elements with the content of 600ppm is not obvious, while the mechanical properties of the annealed microalloys improve relative to pure Cu I.The tensile strength of Cu I-0.06Sn/(Ag、In、 Sb) microalloys and the pure Cu I were 430MPa/(410 MPa、435 MPa、415 MPa)and 330MPa respectively, and fell by only 6.5%/(10.9%、7.4%、1.7%))and 26.7%. For the pure Cu I, the trace Sn, Ag、In and Sb elements with the content of 600ppm improve effectively the heat resistance of microalloys, and the thermal stability temperature of each microalloy rises by about 50℃ relative to Cu I. The microhardness of Cu I-0.06Sn/(Ag、In、Sb) microalloys annealed at 250℃ for 20h were 126.25HV/(118.78HV、129.02HV、121.42HV), and fell by only 4.1%/(9.6%、5.5%、 8.0%). However, the microhardness of the pure Cu I annealed at 250℃ for 5h was 85.72HV, and fell by 34.6%. For the pure Cu I, the trace Sn、Ag、In and Sb elements with the content of 600ppm will not reduce significantly the conductivity of the microalloys. The conductivity of Cu I-0.06Sn/(Ag、In、Sb) microalloys and the pure Cu I annealed at 350℃ for 1h were 94.05%IACS/(99.55%IACS、96.35%IACS、 90.55% IACS)99.55%IACS respectively, which declared that every micoalloy can keep high conductivity. So the combination property in terms of heat resistance, annealing state mechanical properties and conductivity of Cu I-0.06Sn/In microalloy is the best. The difference of the heat resistance and annealing state mechanical properties of Cu I-Sn/In microalloy with the content between 600ppm and 300ppm is small, while the conductivities of them with the content of 300ppm have improved. The heat resistance, annealing state mechanical properties and conductivity of Cu I-0.015Sn-0.015In microalloy fall in between Cu I-0.03 Sn and Cu I-0.03In microalloy, and are close to Cu I-0.03In microalloy.(2)The heat resistance and annealing state mechanical properties between Cu I-0.02Zr-0.04Sn/In and Cu I-0.06Sn/In microalloy is very small, but the conductivity of Cu I-0.02Zr-0.04Sn/In microalloy have improved. The heat resistance, annealing state mechanical properties and conductivity of Cu I-0.02Zr-0.02Sn-0.02In microalloy fall in between Cu I-0.02Zr-0.04Sn and Cu I-0.02Zr-0.04In microalloy, and are close to Cu I-0.03In microalloy.(3)Because of the increase of the purity, the softening temperature of the pure Cu II (That is 250℃) fell by about 50℃ relative to the pure Cu I, and the conductivity of it annealed at 350℃ for 1h arrived at 100%IACS. The heat resistance and annealing state mechanical properties of Cu Ⅱ-0.015Sn-0.015In and Cu I-0.015Sn-0.015In microalloy are almost the same, which explains that the Sn and In elements can improve effectively the heat resistance and annealing state mechanical properties, while the conductivity of the former have improved. The thermal stability temperature of Cu Ⅱ-0.015Sn-0.015In microalloy rose by about 100℃ relative to the pure Cu Ⅱ. The tensile strength of Cu Ⅱ-0.015Sn-0.015In microalloy annealed at 250℃ for 1h arrived at 400MPa, fell by only 12.1%. At the same time, the conductivity of Cu Ⅱ-0.015Sn-0.015In microalloy annealed at 350℃ for 1h arrived at 97.72%. The heat resistance and annealing state mechanical properties of Cu Ⅱ-0.05Sn-0.05In microalloy improved slightly relative to Cu Ⅱ-0.015Sn-0.015 In microalloy, while its conductivity decreased heavily.In conclusion, the Sn and In elements can improve effectively the heat resistance and annealing state mechanical properties, and keep the microalloys high conductivity.