Preparation of ultra-fine molybdenum‒copper composite powders and fine-grained molybdenum‒copper alloys

Abstract

Ultra-fine Mo–Cu composite powders with the different Cu contents (5%, 20%, 40%, mass fraction) were prepared by the method of "carbothermic pre-reduction by insufficient carbon and deep deoxidation by hydrogen". MoO3 and CuO composite oxides were prepared by calcining a mixture of ammonium molybdate and copper nitrate at high temperature, and then most of the oxygen in the calcined products (CuMO4–MoO3) was removed by the carbothermic pre-reduction with carbon black to prepare the pre-reduced Mo–Cu composite powders containing a small amount of MoO2, the existence of which could greatly reduce the residual carbon in the pre-reduction products. Then, the remaining oxygen was removed by hydrogen reduction to prepare the ultra-fine Mo–Cu composite powders with a high purity. The particle size of the prepared ultra-fine Mo–Cu composite powders was about 200 nm. The fine-grained Mo–Cu alloys were directly prepared through the compaction and sintering by using the prepared ultra-fine Mo–Cu composite powders as the raw materials. In the results, the relative density of the fine-grained Mo–Cu alloys increases from 96.3% to 98.5% as the Cu mass fraction increases from 5% to 20% at the sintering temperature of 1200 ℃, and the Mo and Cu phases are homogeneously distributed. The hardness of the Mo–Cu alloys after sintering at 1200 ℃ first increases and then decreases with the increase of the Cu content, since the relative density and copper content have the different influences on the hardness of alloys. Furthermore, with the increase of copper mass fraction from 5% to 40%, the thermal conductivity and electrical conductivity of alloys increase from 48.5 W·m−1·K−1 to 187.2 W·m−1·K−1, and from 18.79% IACS to 49.48% IACS, respectively.

Keywords

• mo–cu alloys
• ultra-fine powders
• relative density
• hardness
• thermal conductivity
• electrical conductivity