Creep Properties of α+α₂ High Temperature Titanium Alloys Designed by the Aid of Thermodynamics

Abstract

Effects of the microstructural and compositional factors on creep properties of α+α₂ titanium alloys were examined using ten Ti-Al-Sn-Zr alloys designed by the thermodynamic calculations based on the sublattice model. From creep tests for these alloys, it was made clear that the α₂ precipitates would be very effective for improving high temperature strength of the α phase titanium alloys. Regression equations to predict creep properties were obtained by multiple regression analysis.
In the furnace cooled (FC) condition, a remarkable decrease in the elongation was observed at around the calculated V_α2 of 0.1 (at 873 K) in room temperature tensile tests. On the other hand, the 0.2% proof stress and the tensile strength increased with increasing V_α2 and good ductility was observed in the solution treated (ST) condition showing applicability of this type of alloys in the ST condition. From these results, the V_α2 of about 0.1 (at 873 K) was proposed as the best design condition for α+α₂ high temperature titanium alloys.