Metal-slag separation strengthening through in situ slagging during CuW composite preparation by metallothermic reduction

Abstract

CuW is widely used in high-voltage electrical switch contacts, rocket nozzle throat linings, electronic packaging materials and other major high-end technologies. CuW is typically fabricated using infiltration and high-temperature sintering methods based on powder metallurgy. As CuW composites fabricated using these methods have the disadvantages of low density and uneven microstructural distribution, the preparation of CuW composites by aluminothermic reduction was proposed. However, some Al₂O₃ inclusions produced by aluminothermic reduction do not effectively combine with the slag-making agent CaO to form a liquid slag phase and remain in the CuW composite, resulting in a small number of Al₂O₃ inclusions in the CuW composites. To overcome this problem, a novel methodology for strengthening metal-slag separation through in situ slagging is proposed. In this study, CuW composites were prepared by metallothermic reduction using Al, AlCa and AlMg as reducing agents. The CuW composites and slag samples were systematically analyzed. The results indicate that the Al₂O₃ particles produced by aluminothermic reduction can be modified in situ into calcium aluminate and MgO·Al₂O₃ with lower melting points by using AlCa and AlMg alloys as reducing agents, which strengthens the metal-slag separation. Moreover, AlCa and AlMg exhibited refining effects on the tungsten particles of the CuW composite, where the effect of AlMg was greater than that of AlCa. The slag obtained using the AlCa alloy as a reducing agent was mainly composed of CaWO₄, CaAl₄O₇ and Ca₄Al₆O₁₂WO₄, whereas that obtained using the AlMg alloy was mainly composed of CaWO₄, MgAl₂O₄ and Ca₄Al₆O₁₂WO₄.

Graphical Abstract