Controlling ζ-Ta4C3-x laminate growth in TaC0.6 ceramic by addition of Cu and its effect on mechanical properties.

Abstract Tantalum carbide ceramics with an overall composition of TaC 0.6 were prepared by hot pressing at 1700 °C for 1 h under 30 MPa pressure with fcc TaC and bcc Ta powder as starting materials. Effects of adding 0–30 mol% Cu on densification, phase formation, microstructural evolution, mechanical properties and electrical conductivity of the obtained composite ceramics were investigated. Full density could be reached at 20 mol% Cu addition and above. Reactions between TaC and Ta resulted in the final phases of hexagonal Ta 2 C and rhombohedral ζ-Ta 4 C 3-x. Plate-shaped ζ laminate grew in both TaC and Ta 2 C and consequently had their sizes confined by the parental grains. Addition of 20–30 mol% Cu could significantly grow the intermediate Ta 2 C grains, hence controlling length of the ζ laminates precipitated in them to form bimodal microstructures consisting of large grains. The 20 mol% Cu composition had a better flexural strength (706 ± 46 MPa) and fracture toughness (9.2 ± 1.7 MPa m1/2). Electrical resistivity at room temperature of the composites decreased with Cu content from 1.03 μΩ m at 0 mol% addition to 0.12 μΩ m at 30 mol% Cu. Highlights • TaC 0.6 ceramics with 0–30 mol% Cu addition were hot pressed at 1700 °C for 1h. • The 10–30 mol% Cu Compositions reached relative densities >97%. • Microstructure consisting of large Ta 2 C and small TaC y grains was formed. • ξ-Ta 4 C 3-x precipitated in both TaC y and Ta 2 C grains. • The 20 mol% Cu composition had good flexural strength and fracture toughness. [ABSTRACT FROM AUTHOR]