Properties of copper based composite materials reinforced with alumina particles and fibers

摘要

In order to manufacture the copper based composite materials reinforced with alumina particles or fibres the squeeze casting method was developed. Porous preforms prepared by wet forming process were infiltrated in special device applying the pressure of 90MPa. At elaborated process parameters composite materials exhibited dense microstructure and proper matrix-reinforcement interface. Copper oxide Cu_2O existing in molten copper, which can improve poor wetting, reacted with alumina forming the CuAl_2O_4 spinels. Composite materials designed for brake disk application were subjected to strength, wear and thermal conductivity examinations. Particle reinforcing significantly improve offset yield strength R_(0.2), which was almost constant in entire temperature range of 20-300 ℃. Increase of bending strength was obtained by reinforcing with fibres whereas particles improve strength only at higher temperature. During dry sliding tests performed under pressures of 0.2 and 1.0 MPa, wear rate of unreinforced Cu was significantly larger than correspondingly composite materials reinforced with 20% of fibres and 50-60% of particles. During friction wear products from counterpart were embedded into the copper based composite subsurface resulting in decreasing of friction coefficient from 0.72 for unreinforced copper to about 0.6 for reinforced composite material. Particles significantly reduced thermal conductivity of Cu though it was still acceptable what provided large heat dissipation from the friction area.