600 ℃/856 MPa Ti-Al-Sn-Zr-Mo-Nb-Ta-W-Si as-cast high-temperature titanium alloy designed from cluster formula

Near-α high-temperature titanium alloys typically exhibit poor tensile strengths，falling below 1200 MPa at room temperature and 750 MPa at 600 ℃. On the basis of the cluster formula α-{[Al-Ti12]（AlTi2）}12+β-{[Al-Ti14]（Mo0.08Si0.4Nb0.1Ta0.32W0.14Sn0.96Zr1）}5 of Ti65 alloy，this work partly replaces the elements in the β-Ti structures unit and adds Zr instead of Ti to enhance high-temperature stability of β phase. Consequently，the composition formulas of α-{[Al-Ti12]（AlTi2）}x+β-{[Al-Ti13Zr1]（Mo0.125Si0.5Nb0.125Ta0.5W0.25Sn0.5Zr1）}（17–x）（x=11，12，13 and 14）series alloys are designed by changing the ratio of α and β cluster unit. The as-cast structure of series alloys is in the form of a basket-weave composed of α plates and residual β phase. As the number of β clusters increases，α plates become increasingly finer，and the tensile strength gradually increases. Among them，the room-temperature tensile strength of Ti-5.3Al-2.5Sn-7.6Zr-0.5Mo-0.5Nb-3.8Ta-0.6Si-1.9W（x=11）reaches 1334 MPa，28% and 21% more than the reported forged IMI834 and as-cast Ti65 alloys. However，the elongation of this alloy is only 1.3%，which is lower than that of forged IMI834 and as-cast Ti65 alloys. The tensile strength is 856 MPa at 600 ℃，26% and 37% more than forged IMI834 and as-cast Ti65 alloys with the identical elongation.