Influence of annealing on the microstructure and Charpy impact toughness of wire arc additive manufactured Ti5111 alloy

The microstructure of wire arc additive manufactured (WAAMed) titanium alloy was characterized by brittle martensitic, which was significantly different from that of wrought alloy. It was generally believed that brittle martensitic was detrimental to the toughness of titanium alloys. In order to obtain WAAMed titanium alloy with excellent combination of strength and toughness, Ti5111 alloy, which is a newly developed deformation twin-ning induced plasticity(TWIP) alloy with an excellent combination of impact toughness and strength, was pre-pared by arc additive manufacturing(WAAM) technology and then annealed at 900 degrees C + air cooling(AC) and 950 degrees C+ air cooling. Microstructure, tensile properties and impact toughness of WAAMed Ti5111 alloy were investigated. Electron backscatter diffraction (EBSD) observation was adopted to identify the deformation twins activated in impact samples. Results showed that as-built WAAMed Ti5111 with excellent toughness was ob-tained, which was 42.8% higher than that of WAAMed Ti-6Al-4V alloy. After annealing, more deformation twins and secondary twins were activated during impact loading, which could effectively improve the toughness of WAAMed Ti5111.