Microstructure And Properties Of Cu - Cr - In Alloy With High Strength And High Conductivity

Copper and copper-based alloys are being widely used because of their properties, such as excellent electrical and thermal conductivity, outstanding resistance to corrosion, and acceptable strength and fatigue resistance, is one of the basic materials of national economic development. With the development of the national economy, an increasing number of industrial and civil applications put forward higher requirements for copper and copper-based alloys, especially with both high strength and high conductivity copper-based alloys received wide attention. In areas such as lead frame materials, high speed railway contact wires, connector, bonding wire have a wide range of needs for high strength and high conductivity copper-based alloys, as well as the increased performance requirements. Research and development of new high strength, high conductivity and high heat resistance copper-based alloys and develop and optimize their process of deformation and heat treatment, have a important significance for the varieties rich of copper alloys and applications requirements such as power electronics and traffic.Micro alloying method was adopted to the new type high strength and high conductivity Cu-Cr-In alloys melting in the non-vacuum conditions with Cr and In as the alloying elements. Mechanical and electrical propertied test were carried out and Optical Microscope and Scan Electron Microscope were used to study the theromechanical process on the effect of microstructures and properties.Main research works and results are as follows:(1) Four Cu-Cr-In alloy with different Indium content(XIn=0.0,0.05,0.10,0.15) were casted in iron mould in non-vacuum conditions. The alloys are in good quality and composition. The residual rate of Cr is above 85%, of In is above 92%. The preparation costs of these alloys are lower.(2) The microstructures of Cu-Cr-In alloys were observed and the Cr rich phase distribution and morphology were described. Cr rich phase formed as the(α+Cr)co-crystal at the phase boundaries in the as-cast microstructures. After homogenization treatment and solution hardening, Cr rich phase homogeneously distributed in the Cu matrix and then uniformly dispersed in the matrix with granular morphology after aging treatment, the Cr rich phase size between 100-200 nm.(3)The cast billets were mechanical processed by extrudingâ†'solid solution hardeningâ†'cold drawingâ†'agingâ†'cold drawing. The products are in excellent overall performance. The tensile strength of Cu-0.70Cr-0.05 In alloy reaches 529 MPa, electrical conductivity reaches 82.72% IACS, softening temperature reaches 500℃,elongation reaches 11% after aged at 450 ℃×180 min; The tensile strength of Cu-0.70Cr-0.10 In alloy reaches 531 MPa, electrical conductivity reaches 82.79% IACS, softening temperature reaches 500℃, elongation reaches 12% after aged at 450 ℃×60 min; The tensile strength of Cu-0.70Cr-0.15 In alloy reaches 544 MPa, electrical conductivity reaches 81.41% IACS, softening temperature reaches 525℃, elongation reaches 12% after aged at 450 ℃×60 min;(4)The mechanical and high temperature softening resistance properties of Cu-Cr-In alloys were improved than Cu-Cr alloy by adding In element. It can be considered that In provides solid solution strengthening and its precipitates at the grain boundaries impede dislocation motion and the deformation process of grain boundary migration.(5)The aging characteristics of alloys were analyses, and obtained the Avrami equation of phase transformation kinetics and the unary, binary conductace equation on aging process. The precipitates mechanism was analyzed, either.