Mechanical property variation of as-built AlSi10Mg and Ti6Al4V manufactured by laser powder bed fusion

Additive Manufacture (AM) is a burgeoning industry on the cusp of being a disruptive alternative to traditional processes for the production of complex repeatable parts, both reliably and in economical volume. Laser powder bed fusion (L-PBF) offers the design freedom to produce complex, high performance and low mass components. The limits of cast and wrought alloys are well understood, but AM lacks this mature knowledge. Design for AM (DfAM) is rapidly developing and is of specific interest to the automotive and aerospace industries for next generation component manufacturer. The complex shapes and lattices feasible with AM can seamlessly introduce thin features and variable structural geometries throughout a design. It has been reported that both thickness and build geometry affect the mechanical properties of alloys used in L-PBF. The extent of this influence still requires further investigation. There is currently very limited open research on the mechanical behaviour of AM alloys with as-manufactured surfaces which cover the combined effect of build orientation and thickness below 5 mm. These variables being the most representative of the complex structures and lattices possible with L-PBF - and increasingly common features in light weighting solutions for component design. This research investigates thicknesses between 1 - 5 mm across three build geometries: 0°, 45° and 90°, with respect to the build plate. These variables capture the broad variation found in complex engineering designs. Two alloys are studied, each interesting in its own right and to enable comparison. These are AlSi10Mg and Ti6Al4V, both common, commercially available light alloys used in L-PBF component manufacture. The results from this study identified increasing mechanical property variability with reduced thickness, notably, Ti6Al4V exhibited a 9% reduction in UTS, something not quantified before in literature. The Weibull method was examined to interpret the property variability and showed high applicability for as-built L-PBF alloys. The findings in this research highlight the complexity of using thin features and the considerations for DfAM of complex geometries when manufacturing with either two commonly used alloys in L-PBF.