Achieving superior high-temperature strength and ductility in near-α titanium alloys by in-situ silicide formation

Abstract

Near-α titanium (Ti) alloys are promising high-temperature (HT) structural materials for aerospace and automotive applications due to their superior specific HT strength and creep resistance. Nevertheless, improving the synergy between strength and ductility at HTs, and thereby expanding the operating temperature range, remains a key challenge in advancing the HT application potential of near-α Ti alloys. Herein, a novel in-situ silicide formation strategy is proposed to achieve superior high-temperature strength and ductility synergy in near-α Ti alloys. Specifically, this strategy is realized through fabricating hypoeutectoid and hypereutectoid TA15 alloys (Ti-6.5Al-2Zr-1Mo-1V, wt.%) containing 0.5 and 1.0 wt.% silicon (Si) via spark plasma sintering (SPS). Results indicate that Si alloying significantly enhances the HT strength of the TA15 alloy without compromising its HT ductility. At 500°C, TA15 alloy with 1.0 wt.% Si achieves a tensile strength of 937.8 MPa with a break elongation of 17.5%, showing superior strength-ductility synergy over most commercial near-α Ti alloys and Ti matrix composites. The superior HT strength-ductility synergy of the Si-containing alloys is attributed both to the silicides in-situ formed during SPS and to additional silicides in-situ formed during HT deformation. Additionally, adding 1.0 wt.% Si into TA15 alloy deteriorated the room-temperature ductility while having no adverse effect on the HT ductility, highlighting the temperature-dependent effects of intergranular silicides on mechanical properties. Furthermore, quantitative analysis of HT strengthening mechanisms is performed, providing insights for designing near-α Ti alloys for HT structural applications.