Effect of normalizing treatment on the microstructure and properties of laser coaxial powder feeding additive manufacturing of Ti6Al4V

To improve the integrated additive manufacturing of titanium alloy structural components in the field of projectiles and missiles, this paper carried out laser coaxial powder-feed additive manufacturing experiments on Ti6Al4V. The optimal forming process parameters were determined, including a laser power of 2.2 kW, a scanning speed of 800 mm/min, a powder feeding speed of 0.9 r/min, and an overlap rate of 50%. The formed specimens were subjected to normalizing treatment at different temperatures. The experimental results show that the microstructures after normalizing at 780°C, 810°C, and 840°C are basketweave structures. With the increase of normalizing temperature, the microstructures become significantly coarser, and the orderliness of the α phase decreases. As the normalizing temperature increases, the tensile strength and yield strength in both the XY and Z directions show a downward trend. The tensile strength in the XY direction is significantly higher than that in the Z direction, but the ductility in the Z direction is better than that in the XY direction. The micro-fracture morphologies in both the XY and Z directions are filled with dimples, which are typical characteristics of ductile fracture.