Effect of heat treatment on microstructure and properties of selective laser melting TA15 alloy

To improve the comprehensive mechanical properties of selective laser melting （SLM） TA15 alloy， the microstructure and mechanical properties of SLM TA15 alloy are studied under annealing conditions of 800 ℃+air cooling， 950 ℃+air cooling， and 1050 ℃+air cooling. The microstructure characteristics of TA15 alloy under annealing conditions are characterized by electron backscatter diffraction. The results show that the orientation and texture of the α phase are not changed after the heat treatment at 800 ℃ or 950 ℃， showing the characteristics of a net basket structure. After the heat treatment at 1050 ℃， the texture with the maximum strength of 9.18 appears along the direction ［0001］， showing the characteristic of the weistenite structure. With the increase of annealing temperature： the width of both α' and α phase increases gradually； the aspect ratio of both α' and α phase increases first and then decreases； the geometrically necessary dislocation density of both α' and α phase decreases gradually； the Vickers hardness of the sample decreases first and then increases， with the highest Vickers hardness of （397.2±10）HV for the unheat treated sample； the strength of TA15 sample decreases gradually； and the elongation increases first and then decreases. After tensile tests， the unheat treated samples show mixed fracture characteristics， the samples treated at 800 ℃ and 900 ℃ show plastic fracture characteristics， and the sample treated at 1050 ℃ show brittle fracture characteristics.