Effect of hatch space on morphology and tensile property of laser powder bed fusion of Ti6Al4V

Abstract

Additive manufacturing shows advantages in fabricating TC4 parts, and hatch space (HS) is one of the basic process parameters for optimization and quality improvement of the final products. In this work, the effect of HS on roughness of the single layer, and top and side surfaces, fracture morphology, tensile properties as well as structure refinement of the printed TC4 parts was studied by experiment systematically. The results show that the trend of the roughness change differs for the single layer and bulk pieces due to the scanning strategy and accumulation effect. Under the optimized process parameters, the total tensile extension can be further increased to more than 15% without decreasing the tensile strength by only increasing HS to 210 μm, whose overlapping rate is about –23%. Under the heat treatment at 800 °C for 2 h, its total extension is the highest among other HS due to lower texture and increased content of β phase, which is caused by low temperature gradient and the solid-state phase transformation, and they lead to less columnar grains, larger interplanar spacing and lattice parameters. Its fracture mechanism is based on the aggregation of micro-voids generated from the printing and tensile processing.