Influence of quenching plus aging on microstructures and mechanical properties evolutions for Ti-Al-Sn-Zr-Mo-Si-Nb-Ta-Er-C near-α high temperature titanium alloys

Abstract

The microstructures and mechanical properties of β-forged and as-heat treated high temperature titanium alloys were carefully investigated. Heat treatments with solution processes varying from 940℃～1010℃ and aging at 650℃ after water quenching were adopted. After forging, prior β grains were squashed and elongated. The content of the primary α phase decreased with increasing solution temperatures, while the content of the transformed β structures increased. After water quenching plus aging processes, super-fine secondary α lamellas with widths of 80～400 nm precipitated in transformed β structure. Secondary nano-scale silicides with a size of ～82 nm re-precipitated. More α2 phase particles with a mean size of 8.00 nm were dispersively and uniformly precipitated. After heat treatment at 1000℃, the room temperature ultimate strength and yielding strength were enhanced by 241 MPa and 228 MPa, reaching 1256 MPa and 1151 MPa, respectively. The high temperature ultimate strength and yielding strength were enhanced by 119 MPa and 128 MPa, reaching 756 MPa and 669 MPa, respectively. The high temperature elongation increased to 13.6%. The excellent mechanical properties compared to the previously studied were ascribed to the precipitation of super-fine secondary α lamellas in βt, dispersed nano-scale silicides and α2 particles, and the superior mixing proportion of Pα and βt acquired after optimization of heat treatments.