High-strength Ti-Al-V-Zr cast alloys designed using α and β cluster formulas

Ti-Al-V-Zr quaternary titanium alloys were designed following α-{[Al-Ti 12 ](AlTi 2 )} 17− n +β-{[Al-Ti 12 Zr 2 ](V 3 )} n , where n =1–7 (the number of β units), on the basis of the dual-cluster formula of popular Ti-6Al-4V alloy. Such an alloying strategy aims at strengthening the alloy via Zr and V co-alloying in the β-Ti unit, based on the original β formula [Al-Ti 14 ](V 2 Ti) of Ti-6Al-4V alloy. The microstructures of the as-cast alloys by copper-mold suction-casting change from pure α ( n =1) to α+α′ martensite ( n =7). When n is 6, Ti-5.6Al-6.8V-8.1Zr alloy reaches the highest ultimate tensile strength of 1,293 MPa and yield strength of 1,097 MPa, at the expense of a low elongation of 2%, mainly due to the presence of a large amount of acicular α′ martensite. Its specific strength far exceeds that of Ti-6Al-4V alloy by 35%.