Mechanical properties of phase-pure bulk Ta4AlC3 prepared by spark plasma sintering and subsequent heat treatment

Abstract

High-purity and bulk Ta4AlC3 ceramics were successfully fabricated by spark plasma sintering (SPS) and subsequent heat treatment, using the raw materials including TaC and Ta2AlC powders. These raw materials were first synthesized by self-propagation high temperature synthesis from elements tantalum, aluminium and carbon black powders, followed by pressure-less sintering. The as-fabricated bulk Ta4AlC3 was relatively stable when subjected to heat treatment at elevated temperature of 1500 °C. Moreover, prolonging the heat treatment time resulted in bigger grain sizes and higher densities of the Ta4AlC3. The flexural strength and the fracture toughness of the Ta4AlC3 fabricated by SPS were found to be 411 MPa and 7.11 MPa·m1/2, respectively. After the heat treatment at 1500 °C for 8 h, the flexural strength and the fracture toughness of the Ta4AlC3 could reach 709 MPa and 9.23 MPa·m1/2, respectively. The special structural characteristics of the ternary ceramics and the increase of density after the heat treatment are the main reasons for the variation in mechanical properties of ternary ceramics.