Enhancing high-temperature strength and ductility of γ-TiAl matrix composites with controllable dual alloy structure

Gamma-TiAl matrix composites can function as promising high-temperature structural materials. In this study, to improve the poor ductility and insufficient strength of composites at high temperatures, they were successfully prepared via powder metallurgy by adding the Ti-6Al-4V alloy. The experimental results indicate that the soft phases of Ti-6Al-4V were surrounded by the hard phase of Ti-48Al-2Cr-2Nb, and the special structure exhibited a unique strain hardening mechanism, which resulted in the high strength and ductility of the composites at high temperature. The 8 wt% Ti-6Al-4V composites were fractured with an elongation approximately 90.65% and tensile strength of 427.75 MPa at 800 degrees C and 5 x 10(-5) s(-1); the elongation and tensile strength were both higher than those of single unreinforced Ti-48Al-2Cr-2Nb alloy. Moreover, with an increase in the deformation strain, the deformation behavior started from the Ti-6Al-4V area, which had good ductility. The dislocation movement was hindered by the Ti-48Al-2Cr-2Nb area, and dislocation accumulation and grain deformation occurred, leading to strength increase. The stress concentration and high-density dislocations were stored in the soft phases, which delayed the initiation and propagation of pores and cracks. Moreover, besides grain sliding, evident dislocation activities occurred; therefore, the high ductility of the composites was obtained.