Effect of microstructure on fracture characteristics of Ti-6Al-2Sn-2Zr-2Mo-2Cr-Si

The effects of intermetallic compounds of Ti3Al (alpha (2)) and silicide se parately on fracture characteristics of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-62222S ) alloy were investigated in this study. The alloys with only Ti3Al and onl y silicide precipitated were established by aging treatments at temperature s of 913 K followed by air cooling and 1088 K followed by water quenching, respectively. X-ray diffraction analysis results showed that the volume fra ction of either Ti3Al or silicide increases with increasing aging time. Ten sile properties, namely, yield stress (0.2 pct proof stress), ultimate tens ile strength, and elongation of as-received alloy are much better than thos e of the aged alloys. The strength of the alloy with only Ti3Al is better t han that of the alloy with only silicide, while elongation of the alloy wit h only silicide is better than that of the alloy with only Ti3Al. Fracture toughness, J(IC), of the alloy with only silicide is better than that of th e alloy with only Ti3Al. The intergranular fracture appears in the alloy wi th only Ti3Al. Coarsening of Widmanstatten alpha structure and increasing d uctility of beta phase during aging are considered to be effective for incr easing fracture toughness.