Effect of processing parameters on formability of Ti6Al4V at constant volumetric energy density by laser powder bed fusion

Volumetric energy density establishes connections among crucial process parameters, such as laser power, scanning speed, layer thickness, hatch spacing, etc., in laser powder bed fusion processing. The impact of laser power and scanning speed on the melt pool shape, surface morphology, porosity, and microstructure of the as-built samples was investigated while maintaining a constant volumetric energy density. At a constant VED, the depth of the melt pool progressively deepens with increasing laser power, while concurrently, the width of the melt pool tends to diminish. With a laser power of 170 W, the height of the melt pool approaches the layer thickness of 40.0 μm, providing adequate overlap between the two layers. Adequate melt pool height ensures the prevention of incomplete fusion holes and guarantees sample densification. The root width of the melt pool was 41.0 μm and 63.2 μm for laser powers of 100 W and 170 W, respectively. Insufficient overlap between melt pools leads to unfused holes, the primary cause of increased specimen porosity. Distinct processing parameters result in varying times and types of thermal cycles, significantly influencing the degree of refinement of α′-acicular martensite.