Predicting part-level thermal history in metal additive manufacturing using graph theory: Experimental validation with directed energy deposition of titanium alloy parts

The objective of this paper is to experimentally validate thegraph-based approach that was advanced in our previous workfor predicting the heat flux in metal additive manufacturedparts. We realize this objective in the specific context of thedirected energy deposition (DED) additive manufacturingprocess. Accordingly, titanium alloy (Ti6Al4V) test parts(cubes) measuring 12.7 mm × 12.7 mm × 12.7 mm weredeposited using an Optomec hybrid DED system at theUniversity of Nebraska-Lincoln (UNL). A total of six test partswere manufactured under varying process settings of laserpower, material flow rate, layer thickness, scan velocity, anddwell time between layers. During the build, the temperatureprofiles for these test parts were acquired using a singlethermocouple affixed to the substrate (also Ti6Al4V). Thegraph-based approach was tailored to mimic the experimentalDED process conditions. The results indicate that thetemperature trends predicted from the graph theoretic approachclosely match the experimental data; the mean absolutepercentage error between the experimental and predictedtemperature trends were in the range of 6% ~ 15%. This workthus lays the foundation for predicting distortion and themicrostructure evolved in metal additive manufactured parts as a function of the heat flux. In our forthcoming research we willfocus on validating the model in the context of the laser powderbed fusion process.