Synthesis of high density ultrafine W/Cu composite alloy by mechano–thermochemical process

Abstract

It is difficult to obtain a high density W/Cu composite without the addition of a sintering activator as there is no mutual solubility but a great difference in melting temperature and specific gravity. Ultrafine starting powders are needed in order to achieve the desired full density W/Cu composite. Recently, the authors have developed a new manufacturing process to achieve the full density ultrafine W/Cu composite alloy by combining a thermochemical and a mechanical process (mechano–thermochemical process). W/Cu oxide and W/Cu metal composite powders, which are loosely agglomerated homogeneous clusters of nanoscale sized particles, can be synthesised by a thermochemical process and then these powders are treated again by a mechanical process to obtain ultrafine powders. In the case of the mechano–thermochemical process, a sintered W/Cu composite alloy, obtained from the W/Cu oxide composite powder passing through a multistep reduction process, shows a higher density than that produced from the W/Cu metal composite powder. A full density W + 20 wt-%Cu composite alloy with an average W particle size of 1 μm can be obtained without the addition of a sintering activator through a combination of the mechano–thermochemical process and liquid phase sintering.