Influences of Post-processing, Location, Orientation, and Induced Porosity on the Dynamic Compression Behavior of Ti–6Al–4V Alloy Built Through Additive Manufacturing
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This paper investigates the dynamic compression behavior of Ti–6Al–4V alloy built through powder bed fusion (PBF) additive manufacturing. Samples of 45 different conditions were examined: Builds of three different orientations (vertical, horizontal, and 45° tilt), built in five different locations around the build plate (four corners and center), in as-built, stress-relieved and hot isostatically pressed conditions. High strain rate behavior was evaluated using a Split-Hopkinson Pressure Bar testing system. The as-built builds showed significant scatter with respect to both orientation and location owing to high internal stresses. Stress relief treatment resulted in a locationally uniform response but the retained columnar structure gave rise to higher strength in 45° tilt builds, along with a higher propensity for failure by shear localization. Hot isostatic pressing was found to be a necessary treatment for a truly homogeneous response that was independent of orientation and location on the build plate. A second series of samples were built in porous sandwich form with modification of processing parameters in the core to produce varying amounts of porosity. Porous samples exhibited greater energy absorption per unit volume than fully dense samples. Largest energy absorption capacity was observed in the samples with minimal porosity due to delayed failure without a significant loss in strength.
KeywordsAdditive Ti64 Dynamic properties Post-processing treatments Orientation and location Porosity effect
The work was performed under a cooperative agreement between the Army Research Laboratory and the University of North Texas (W911NF-16-2-0189). We also acknowledge the Materials Research Facility at UNT for microscopy facilities.
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