Structural features of tantalum carbide-copper composites obtained by liquid phase-assisted spark plasma sintering

Abstract

Nearly fully dense metal-ceramic composites were synthesized by high-energy ball milling of (2Ta–C)+Cu powder mixtures followed by liquid phase-assisted spark plasma sintering (SPS). The concentration of copper in the starting mixtures was 30 wt% and 50 wt%, while the molar ratio of Ta/C was 2/1. The products of milling consisted of dense composite agglomerates. The agglomerates formed from (2Ta–C)+30 wt% Cu contained ∼10 wt% of iron introduced as contamination during milling. In the sintered composite obtained from (2Ta–C)+30 wt% Cu, Fe5Ta3 was present along with TaC and Ta2C. The reinforcing phase in the composite obtained from (2Ta–C)+50 wt% Cu was Ta2C. During SPS, the formation of melt locally at the inter-particle contacts enabled consolidation of the agglomerates into compacts with a low residual porosity (2–5%). Composites obtained in this work possessed interesting structural features: a Cu-rich network penetrated the structure such that each composite particle was surrounded by a Cu-rich layer. The Vickers hardness of the sintered composites obtained from mixtures containing 50 wt% Cu and 30 wt% Cu was 490 ± 50 HV1 and 715 ± 55 HV1, respectively.