Role of refractory elements in near-alpha titanium alloys on high temperature mechanical properties

Zhao Huvelin ,N Horézana,C Gouroglian,S Naka

doi:10.1051/matecconf/202032104018

Abstract

The effect of Tungsten (W), Tantalum (Ta) and simultaneous addition of Germanium (Ge) and Silicon (Si) on the microstructure evolution, tensile and creep properties of the near-alpha alloy Ti-5.7Al-3.9Sn-3.7Zr-0.7Nb-0.5Mo-0.35Si-0.05C have been investigated at high temperatures up to 650°C. Microstructural characterizations following solution treatment at 1050°C for 2 hours with oil quenching and aging treatment at 700°C for 2 hours followed by air cooling, highlighted that the additions of refractory elements such as W and Ta led to a decrease of both the volume fraction of the primary alpha phase (ap) and its average size. Tensile tests performed up to 650°C revealed a significant improvement in tensile strength with additions of W and Ta, even though a decrease of ductility has been also detected. Creep tests carried out at 600°C under a constant stress of 200 MPa pointed out that, refractory elements, Ge and Si have a beneficial effect on both primary and steady-state creep strain rates.

Highlights

Near-alpha titanium alloys are promising candidates for aerospace applications owing to their high specific strength, good corrosion resistance and high temperature resistance [1]
These studies demonstrated that the solid solution strengthening and the formation of a2 phase are effective in improving high temperature strength, but degrade the ductility of the material [10,11] probably due to the lower symmetry of its DO19 crystal structure
The volume fraction of primary alpha phase was estimated at 34% and 29% in 834M and 834 alloys, respectively

Summary

Introduction

Near-alpha titanium alloys are promising candidates for aerospace applications owing to their high specific strength, good corrosion resistance and high temperature resistance [1]. Numerous works were focused on the influence of alpha stabilizing alloying elements such as Ga, Sn, Hf and Zr on the high temperature mechanical properties of the near-alphaa titanium alloys [9,10, 12]. These studies demonstrated that the solid solution strengthening and the formation of a2 phase are effective in improving high temperature strength, but degrade the ductility of the material [10,11] probably due to the lower symmetry of its DO19 crystal structure.

Results

Conclusion