Microstructure and High-Temperature Properties of TC31 Alloy Manufactured by Laser Melting Deposition

Abstract

This paper presents a comprehensive study conducted to optimize the mechanical properties for a laser-melting-deposition fabricated TC31 (Ti-Al-Sn-Zr-Mo-Nb-W-Si) alloy, which is a newly developed high-temperature alloy used in the aerospace industry. The results showed that the laser melting deposition (LMD)-built sample exhibited columnar structures with very fine α-laths inside. Annealing and solution treatment resulted in an α+β lamellar structure consisting of α-laths and β-films, of which thicknesses depended on the temperature. Solution treatment and subsequent aging did not significantly change the lamellar structure. However, aging at 650 °C led to the formation of nanoscale α precipitates within the remaining β, while aging at 750 °C resulted in coarse α precipitates. The solution-treated samples exhibited the best combination of strength and ductility at room temperature, ultimate tensile strength of 1047 MPa, and elongation of 13.0%, which is superior to the wrought TC31 counterparts. The sample after solution treatment at 980 °C and subsequent aging at 650 °C obtained an attractive combination of strength and ductility both at room temperature and high temperature due to the synergistic effect of the soft α + β lamellar structure and hard fine α precipitates. These findings provide valuable information on developments of LMD-built TC31 alloy for aerospace applications and shed light on AM of other titanium alloys with desirable high-temperature properties.

Keywords

• laser melting deposition
• TC31 alloy
• alpha phase
• post-heat treatments
• high-temperature properties
• microstructure–tensile properties relationship