Strength and Ductility Optimization of Laser Additive Manufactured Metastable Β Titanium Alloy by Tuning Α Phase by Post Heat Treatment

The metastable beta titanium alloy Ti-5Mo-5V-8Cr-3Al (TB2) was fabricated by laser melting deposition (LMD). alpha phase was tuned by post heat treatment (PHT) in order to obtain a good combination of strength and ductility of laser melting deposited (LMDed) TB2 alloy. This study demonstrated that TB2 alloy exhibited fully equiaxed beta phase after LMD, which possessed good ductility (approximate to 18.2%) with ultimate tensile strength (sigma(UTS)) of 811 MPa. The beta solution plus aging treatments resulted in higher strength (sigma(UTS) approximate to 1136-1312 MPa) in comparison with the (alpha+beta) solution plus aging treatments (sigma(UTS) approximate to 1037 MPa) because of higher-density acicular a phase with finer size (width similar to 200 nm). Two-step aging resulted in improved ductility (approximate to 9.8-12.9%) in comparison with the one-step aging (approximate to 2.0%) due to coarsening of alpha phase. Finally, beta solution plus two-step aging was proved to be appropriate for LMDed TB2 alloy to achieve a good combination of strength (sigma(UTS )approximate to 1136 MPa) and ductility (approximate to 9.8%).