Design of Near α-Ti Alloys with Optimized Mechanical and Corrosion Properties and Their Characterizations

The designed alloy Ti-10.56%Al-2.08%Zr-0.80%Sn-0.88%Mo-0.51%Si (mol%), modified alloy Ti-10.81%Al-4.80%Zr-1.23%Sn-0.76%Cu-0.35%Si (mol%) and reference alloy Ti-10.52%Al-2.07%Zr-1.1%Sn-0.2%Mo-0.76%Si (mol%) with the same bond order (Bot) value of 3.49 and different d-orbital energy level (Mdt) values of 2.43, 2.42 and 2.42 were proposed and their mechanical and corrosion properties were compared in the present study. The ultimate tensile strength (σUTS) and fracture strain (ɛf) values of the three near α-Ti alloys at both as-cast and solution-treated conditions were 989 and 1118 MPa and 11.6% and 3.4% for the designed alloy, 993 and 1354 MPa with 13.5% and 2.3% for the modified alloy and 991 and 1238 MPa with 12.7% and 3.1% for the reference alloy, respectively. The thickness of corrosion layers of the solution-treated designed, modified and reference near α-Ti alloys after immersion in hot salts for 28.8 ks were measured at 3.06, 3.68 and 4.89 µm. The comparable mechanical properties and improved hot salt corrosion resistance ability of designed and modified alloys compared to those of the reference alloy were obtained by considering their Bot and Mdt values; this might lead to the development of alternative near α-Ti alloys to conventional materials.