Die-cast copper matrix composite materials
Die-cast copper-based composites are novel materials made by die-casting a copper or copper alloy matrix with various reinforcements. Due to the excellent electrical and thermal conductivity of the copper matrix and the high strength and wear resistance provided by the reinforcements, they are highly sought after in high-end fields such as electricity, aviation, and machinery. Copper, with a conductivity of up to 58 MS/m and a thermal conductivity of 401 W/(m・K) , is an ideal matrix material for both electrical and thermal conductivity. The addition of reinforcements such as tungsten carbide, aluminum oxide, and carbon fiber significantly enhances the material’s mechanical properties. For example, in the manufacture of high-voltage switch contacts, copper-based composites reinforced with tungsten carbide particles achieve a hardness exceeding 200 HV , three times that of pure copper, while maintaining a conductivity exceeding 90% , effectively addressing the inherent strength limitations of pure copper.
From the perspective of material system design, it is crucial to match the matrix selection and reinforcement of die-cast copper-based composites. Commonly used copper matrices include red copper (pure copper), brass (Cu-Zn alloy), bronze (Cu-Sn alloy), etc. Among them, brass has become the first choice for die-casting process due to its good fluidity and moderate cost. The selection of reinforcing phase must take into account both interface compatibility and performance requirements. Tungsten carbide particles have good wettability with the copper matrix and a hardness of more than 2000HV. They are often used in situations requiring high wear resistance; carbon fiber reinforced copper-based composites have higher specific strength and are suitable for lightweight structural parts. Research data shows that when the volume fraction of tungsten carbide particles is 20%, the tensile strength of the composite material can reach 600MPa, which is much higher than the 300MPa of brass, and the wear resistance is increased by 4-6 times.
The unique nature of the die-casting process places stringent demands on the molding of copper-based composites. Copper has a melting point of 1083°C, far higher than that of metals like aluminum and zinc. This necessitates higher mold temperatures (typically 300-400°C) and injection pressures (100-150 MPa) to ensure melt fluidity. To address the issue of oxidation and agglomeration of the reinforcing phase at high temperatures, modern processes often utilize inert gas-protected melting. Mechanical stirring and ultrasonic vibration combined dispersion techniques are used to control the agglomerate size of the reinforcing phase to below 50 μm. Furthermore, copper-based composites exhibit significant shrinkage (approximately 1.5%-2.0%), requiring sufficient compensation in mold design to avoid cracks or shrinkage cavities in the casting.
Across various applications, die-cast copper-based composites are gradually replacing traditional copper alloys and other metal materials. In the power industry, motor commutators made of composite materials have a service life 2-3 times that of pure copper components and can withstand higher current densities. In aerospace, composite drive shafts offer 30% greater fatigue strength than steel while being 40% lighter, effectively reducing aircraft energy consumption. According to industry statistics, by 2024, the global market share of die-cast copper-based composites in power equipment will reach 60%, with a penetration rate exceeding 45% in ultra-high voltage transmission equipment.
Despite its significant advantages, the development of die-cast copper-based composites still faces challenges. High-temperature die-casting results in a mold loss rate 3-4 times that of aluminum alloy die-casting, resulting in high equipment maintenance costs. Interfacial reactions between the reinforcement phase and the copper matrix are difficult to completely avoid at high temperatures, easily forming brittle compounds (such as Cu3W), which affect material properties. In the future, with the application of new high-temperature resistant mold materials (such as ceramic-coated molds) and breakthroughs in low-temperature die-casting technology, production costs are expected to decrease. Furthermore, precise dispersion technology for nanoscale reinforcement phases will further enhance the overall performance of composite materials and promote their application in more high-end fields.
