Thermomechanical processing and heat treatment of Ti–6Al–2Sn–2Zr–2Cr–2Mo–Si for structural applications

Titanium alloy Ti–6Al–2Sn–2Zr–2Cr–2Mo–Si (Ti–6–22–22S) is an alpha–beta alloy that is being used as an advanced structural material in new and developing aerospace applications. The alloy has good hardenability in heavy sections and possesses a higher elastic modulus and tensile strength than Ti–6Al–4V and other alpha–beta Ti alloys. Ti–6–22–22S also has a good combination of strength, ductility, toughness and durability. Plate and sheet are the most commonly specified product forms, however, the alloy is readily producible as billet, forgings, bar and extrusions. For optimum strength and ductility, alpha–beta thermomechanical processing (TMP) and heat treatment (HT) is generally utilized, whereas a beta TMP or beta HT is used for optimum fracture toughness and fatigue crack growth resistance. A review of various TMP routes and heat treatments on Ti–6–22–22S and the resultant structure and properties is presented in this paper.