Effect of Intra-Build Design Parameters on the Fracture Toughness
Properties of EBM Ti6Al4V
Abstract
Metal Additive Manufacturing technologies provide new opportunities for
manufacturing complex components. However, the limited and scattered
data on damage tolerance behavior is hindering adoption in safe-critical
applications. A design of experiments (DOE) is used in this study to
provide an understanding of the Electron Beam Melted (EBM) Ti6Al4V
fracture toughness properties. Three builds comprised of 150 compact
tension samples were printed representative of the EBM build chamber,
followed by surface machining, microstructural characterization, X-ray
microcomputed tomography (µCT), and fracture toughness testing per ASTM
E399. Analysis of Variance (ANOVA) statistics on the influence and
interaction of intra-build design parameters on the As-Built and
Machined samples showed orientation, build location, and geometry to
contribute to property variation. EBM fracture toughness reported an
average of 65 MPa√m, with an increase in build height and proximity to
the center of the build envelope. The location- and size-dependent
properties resulted from changes in microstructure and porosity
throughout the build space. While intra-build design variation was
present, the EBM Ti6Al4V fracture toughness properties reported a 10%
overall variation comparable to wrought and cast alloys. The extensive
experimental work in this study shows EBM Ti6Al4V to be a repeatable and
reliable alloy for use in load-bearing applications.