Face centered cubic substructure and improved tensile property in a novel β titanium alloy Ti–5Al–4Zr–10Mo–3Cr

A novel metastable β-Ti alloy based on Ti–Al–Zr–Mo–Cr system was successfully designed and fabricated. Superior combination of high strength (UTS = 1534-1198 MPa) and ductility (El = 7.0%–20.9%) is achieved in this alloy. After high reduction β transus forging and subsequent heat treatment, a multi-scale distribution of α phase is displayed which contains micro-scale elongated primary α (α_p), sub-micro α rod (α_r) and nano-sized α platelets (α_s). Detailed selected area electron diffraction (SAED) pattern and high resolution-TEM analysis show the production of FCC substructure inside α_p and α_r with an orientation relationship of <0001>_hcp//<001>_fcc, {112‾0}_hcp//{2‾20}_fcc, {101‾0}_hcp//{220}_fcc. Two variants of FCC lamella are discovered which is related by a 120° rotation around <001> axis. The effect of microstructure on the improved strength-ductility combination is briefly discussed. Both FCC lamella and multi-scale distribution of α phase could create an effective strain partition during plastic deformation and increase the ductility. High strength originates from the distribution of high fraction nano-scaled α_s which could effectively hinder dislocation slip in β matrix.