Research progress of high strength and high conductivity copper alloy

Abstract: This article introduces the common applications, basic properties, strengthening methods and preparation methods of high-strength and high-conductivity copper alloys. At the same time, the development trend of high-strength and high-conductivity copper alloys is prospected.


1. Introduction

As one of the earliest metal materials used in human history and one of the most widely used metal materials to date, copper and copper alloys have been widely Is used in important industrial sectors such as electrical engineering, electric power, and machinery manufacturing . However, with the development of science and technology and modern industry, higher requirements have been placed on the comprehensive performance of copper and copper alloys. Large-scale integrated circuit lead frames, rotor wires for large high-speed turbine generators, contact materials, electrodes for various spot welding and roll welding machines, overhead wires for large electric locomotives, commutators for power tools, high-voltage switch reeds, Microwave tubes and components for aerospace vehicles require materials that have high strength and hardness while maintaining their own excellent electrical conductivity. Components in the heat exchange environment, such as injection ignition orifices in power plant boilers, gas torch nozzles, continuous casting machine crystallizer linings, and high thrust rocket engine combustion chamber linings, etc., not only require materials with very good electrical conductivity and Thermal conductivity, but also requires the material to have a sufficiently high thermal strength. Therefore, people are constantly exploring functional materials with excellent comprehensive physical and mechanical properties-high strength and high conductivity copper alloys.


Since the 1970s, foreign developed countries have conducted a lot of research and development work on high-strength and high-conductivity copper alloys. They have developed a number of series of products for different purposes and have produced them commercially, including the United States, Japan, Germany Is the main producer and exporter.

China's research in the field of high-strength and high-conductivity copper materials started late, and many research work is still in the experimental stage, most of which have not yet formed an industrial scale, making most of our high-performance copper materials dependent on imports. China is a country with large copper resources and has many copper processing enterprises. Therefore, it is of great strategic and practical significance to research and develop high-performance copper materials and gradually establish a material science system with independent intellectual property rights.


2.  Application of high strength and high conductivity copper alloy

Copper and copper alloys have many aspects and outstanding excellent performance. Such as: high electrical conductivity and high thermal conductivity; antimagnetic; high mechanical properties and plasticity; more corrosion resistance; good alloying ability, alloying can improve temperature, toughness, wear resistance, elastic , And can maintain high electrical conductivity, thermal conductivity; antibacterial performance, regeneration performance .

With the development of science and technology, higher requirements have been placed on the comprehensive performance of copper and copper alloys. How to increase the strength of copper as much as possible while maintaining some excellent properties of pure copper is an important direction of materials science research.


2.1  Lead frame material

The lead frame is an important component in the packaging of semiconductor components and integrated circuits. Its role is to support the chip, realize the electrical communication between the chip and the outside world, and dissipate heat during operation. In order to ensure the reliability and durability of the circuit, the lead frame material needs to have high tensile strength, good electrical conductivity, high thermal conductivity, and excellent ductility. At present, copper alloy frame materials account for more than 80% of integrated circuit lead frames. The globally developed copper alloy lead frame materials mainly include Cu-Fe-P, Cu-Cr-Zr, Cu-Ni-Si, Cu-Cr-Sn, Cu-Ni-Sn and other series .


2.2  Contact wire material

The contact line is a sliding feeder for electrified railways, industrial and mining electric locomotives, etc. Its function is to directly send electric current to the electric locomotive through sliding friction with the electric vehicle hand pantograph sliding plate, and at the same time it must withstand suspension tension, additional force, wear and consumption, etc., so Contact wire materials need to have excellent electrical conductivity, high tensile strength, good wear resistance and corrosion resistance. Because high strength and high conductivity copper alloys have excellent electrical and mechanical properties, copper alloys are widely used at home and abroad as contact wire materials. Wu Ting of Shanghai Dianke Industrial Materials Co., Ltd. prepared copper-based electrical contact material copper-tungsten-tungsten carbide / copper double-layer products by powder metallurgy. The copper layer is flat and the thickness requirement is 0.6mm. The point contact materials produced by it have been realized It was put into production and started to be used.


2.3 Resistance welding electrode material

Resistance welding is to press the upper and lower electrodes against the two sides of the two metal plates to be welded. In a short time, a strong current generates a high contact resistance heat between the two plates, so that the two metal plates are processed. High-temperature welding occupies a very important position in welding production such as automobiles, home appliances, and machinery manufacturing. With the extensive use of automatic welding machines and manipulators in modern industrial production, welding is completed at high speeds and high beats, so that the resistance welding electrode frequently contacts with the workpiece under high temperature and high pressure. Softening point and high conductivity electricity.


3.  Strengthening method of high strength and high conductivity copper alloy

High-strength and high-conductivity copper alloys are a class of functional materials with excellent physical and mechanical properties. Its tensile strength (600 ~ 800MPa) is 2 ~ 10 times that of pure copper, and its conductivity is 50% ~ 95% of pure copper, generally higher than 80% IACS. High copper alloy has excellent physical and chemical properties, high strength and good plasticity, and has the characteristics of anti-oxidation, anti-fatigue, anti-creep, no hydrogen embrittlement, anti-stress relaxation, anti-stress corrosion, etc. The main problem faced by the research and development of high-strength and high-conductivity copper alloys is the mutually opposed relationship between the strength and conductivity of copper alloys, making it difficult to balance each other. No matter which method is adopted to improve the strength of the copper alloy, its conductivity will inevitably decrease to a certain extent; similarly, when the conductivity of the copper alloy is increased, its alloy strength will inevitably decrease. Therefore, the basic idea of ​​strengthening copper alloys is to increase the strength of copper alloy materials as high as possible while maintaining the original high conductivity. Choose the appropriate strengthening method according to the requirements of different application environments to ensure that the electrical conductivity of the alloy is reduced to the smallest possible extent while the strength of the copper alloy material is maximized to solve the strength and conductivity of the copper alloy The contradiction between rates.


The strengthening methods of copper alloy can be divided into two categories: alloying method and composite material method, usually including deformation strengthening, solid solution strengthening, dispersion strengthening, aging strengthening, fine grain strengthening and fiber composite strengthening. The high-performance copper alloys that have been developed so far can be divided into two major categories of high-performance aging strengthened copper alloys and high-performance copper-based composite materials. High-performance copper-based composite materials mainly include particle dispersion-strengthened copper-based composite materials and fiber-reinforced copper-based composite materials. High-performance aging strengthened copper alloys include Cu-Zr-based, Cu-Cr-based, Cu-Cd-based, Cu-Ni-based, Cu-Fe-based, Cu-Mg-based Cu-Nb-based alloys.


3.1  Alloying method

The alloying method is to add an alloy element with low solid solubility to copper through high-temperature solution treatment, and solute atoms dissolve into the copper matrix to form a supersaturated solid solution, thereby reducing the conductivity and increasing the strength. Through mechanical processing and aging treatment in the subsequent steps, a large number of alloy elements precipitate precipitated phases and are dispersed in the copper matrix. The conductivity of the alloy increases rapidly, and the aging precipitates play a role in strengthening to increase the strength of the alloy.

The alloying method is a method for preparing traditional high-strength and high-conductivity copper alloys. It achieves the purpose of strengthening the copper matrix by means of solid solution strengthening, precipitation strengthening, fine grain strengthening, deformation strengthening and excess phase strengthening.