Influence of α+β solution treatments on Ti65 ultrathin sheets: Silicide precipitation, mechanical behaviour and novel {101¯1} twinning system

To cope with the urgent demands of the aerospace industry for lightweight and excellent high-temperature performance titanium alloy components, the microstructure evolution, silicide precipitation and mechanical behaviour of a novel high-temperature Ti65 titanium alloy ultrathin sheet with different heat treatments were systematically investigated. Submicron (Ti,Zr)6Si3 silicides are observed after solution treatments followed by air cooling, leading to a decline and significant fluctuations in tensile properties. For furnace cooling samples, (Ti,Zr)5Si3 silicide crossing grain boundaries and (Ti,Zr)6Si3 silicide near grain boundaries are observed after solution treatment at 950 °C. When the solution temperature increases to 1010 °C, the third silicide (Ti,Zr)3Si appears near dislocations. The combined effect of the strong size effect of the alloy ultrathin sheet and silicide precipitation results in great performance fluctuation, sharp drop of ductility and even brittle fracture. In addition, silicide precipitation differs little with various holding time during low-temperature solution treatment. Moreover, novel {101¯1} twins appear after the rolling process at 990 °C and are only inside coarse basal texture α grains, with an axis—angle pair of 65° 〈844¯3〉.