Enhancing as-built microstructural integrity and tensile properties in laser powder bed fusion of AlSi10Mg alloy using a comprehensive parameter optimization procedure

The importance of a thorough and systematic approach to parameter optimization in the laser powder bed fusion (LPBF) of AlSi10Mg alloy is demonstrated, particularly in the event of varying the physical attributes of the input powder (i.e., upon changing from one powder source to another). The proposed approach involves the effective use of prevalent energy density/enthalpy models complimented by an in-depth microstructural and mechanical characterization. Using a formulation derived from the functioning characteristics of a pulsed-wave laser system, a reliable volumetric energy density (VED) model is developed, from which a trend in VED-porosity relationship is identified. Particularly, it is shown that a multi-stage optimization through porosity minimization, followed by a microstructural screening step, can successfully result in achieving excellent tensile properties; In the first and second screening steps, using a VED/enthalpy approach, the as-built porosity content is correlated with VED, and then a number of optimized parameter sets are identified; In the third screening step, the number of potentially optimized parameter sets is reduced via a microstructural screening for the least amount of lack of fusion and lowest density of melt pool boundaries; In the fourth screening step, through tensile testing, the final parameter set representing the "best optimized" condition is identified (i.e., exhibiting an excellent combination of ultimate tensile strength and elongation-to-fracture of ~461 MPa and ~11.5%, respectively). Furthermore, it is demonstrated that the optimized VED value is a strong function of the physical attributes of the powder source, e.g., the particle morphology and size distribution (the effect of which will be thoroughly investigated in a separate study). The novel parameter optimization methodology described here represents a standard practice that can be potentially adopted in the LPBF processing of many metallic alloys.