Preparation of Ultrafine Cu Base Intermetallic Compound Particles by Arc Plasma Method and Their Properties

Abstract

Ultrafine powders consisting only of an intermetallic compound were formed in the limited Cu–M (M=Al, Ga, Sn or Ge) systems by an evaporation method in which an arc plasma was used as a heat source to evaporate prealloyed Cu-based binary alloys. The limitation of the Cu–M systems is due to the criterion in which the ratio (R) of the vapor rate for molten M metal to that for molten Cu is in the range of 0.234 to 3.58. As R approaches 1.0, the resulting phase tends to coincide with the phases at high temperatures in the corresponding Cu–M equilibrium phase diagram. The compound particles obtained in the present study are Cu9Al4, Cu9Ga4, CuGa2, Cu6Sn5 and Cu3Ge. The particles have a spherical shape and the particle size is below 180 nm. The ultrafine Cu9Al4 particles have a high resistance against oxidation, which is much superior to that for ultrafine Cu particles, and remain unchanged by heating up to 773 K in air. The result that the high resistance against oxidation for the Cu-rich ultrafine particles is obtained in the compound phase is important in the development of ultrafine compound particles.