Spatially dependent properties in a laser additive manufactured Ti-6Al-4V component

Automotive and aerospace sectors have provided a strong product pull for advancing powder bed fusion technologies. However, as these technologies mature towards large-scale production, issues of build consistency and surface finish are of concern. In order to study these issues, a Ti-6Al-4V mini impeller was fabricated using laser additive manufacturing. The primary objective of this work was to quantify and correlate the variation in mechanical properties and microstructure across and along different locations in the component. Hardness measured at various build locations revealed a stronger hub (highest value: 428 HV) with lower spatial variations in comparison to the blade (highest value: 415 HV). Additional examinations to assess anisotropy showed an average hardness of 397 +/- 11 and 385 +/- 8 HV along the blade build (Z) and longitudinal (X) directions respectively. Region and direction specific uniaxial tensile testing of the samples indicated a strong hub bottom with yield strength (YS) of 1193 MPa, ultimate tensile strength (UTS) of 1310 MPa, and a total elongation of 5.5% in the longitudinal direction. Although the low elongation value correlates well with previous studies, strength is significantly higher and is attributed to having a complete martensitic structure induced by the high cooling rates experienced at the build-substrate interface. On the other hand, YS, UTS and total elongation in the blade were recorded as 978 MPa, 1096 MPa and 9.12%, respectively, along the build direction. Microstructure in the blade region consisted of alpha' and alpha+beta. When compared to the polished specimen in the blade, its unpolished counterpart yielded at 896 MPa, had UTS of 1018 MPa, and elongation of 6.24%. An understanding of the reduction in performance of the unfinished blade would help in deciding the need for surface finishing operations after fabrication. (C) 2015 Elsevier B.V. All rights reserved.