Effects of heat treatment and carbon nanotubes content on microstructure and mechanical properties of CNTs/Ti–Mo–Nb–Al–Si composites

In this paper, carbon nanotubes (CNTs) reinforced Ti–12.8Mo–2.1Nb–2.7Al–0.2Si (TB8) matrix composites were synthesized by low-energy ball milling and cold pressing sintering. Based on theoretical calculation and thermodynamic simulation method to obtain phase transition points, CNTs/TB8 composites were subjected to a solid-solution and aging treatment. The effect of heat treatment and CNTs content on microstructure and mechanical properties of the composites was investigated. The results indicated that 0.5 wt% CNTs/TB8 composite formed α + β phase structure after different heat treatment processes, α phase dispersed in the β phase, grain refinement was distinct, and the microhardness of composite was significantly improved. It had the effect of solution strengthening and dispersion strengthening. The composites’ microhardness was the highest, reaching 615.3HV after 850 °C/3 h/AC and 550 °C/6 h/AC heat treatment. Under these conditions, with the CNTs content increasing, the microhardness of composite increased initially and then decreased. The microhardness of the composite containing 1.0 wt% CNTs reached 635.1HV, which was an increase of 21.9% compared to without executing heat treatment. In addition, the compression property of the titanium matrix composite at room temperature was excellent; the compressive strength and the fracture strain were 1263 MPa and 18.5%, respectively.