Showing papers in "Advanced Materials Research in 2021"

Cellular Automata Analysis of Effects of Substrate Conditions on Microstructure and Texture Evolution during Selected Laser Melting

Abstract: A Cellular Automata Finite Difference (CAFD) method was applied to analyze the effects of substrate grain size and texture on the microstructure and texture evolution during additive manufacturing. It was found that the grain size within the substrate is only effective at a short distance. Grains developed from the surrounding powders can lead to an almost similar microstructure away from the substrate. Texture evolution during build-up can be explained by the two main components of {001}<100> and {011}<100>. Development of the former and the latter components can be described by the competitive growth mechanism at the regions beneath and on the sides of the melt-pool, respectively. As a result, the former component is more pronounced at the higher ratios of the melt-pool width to the hatch distance. An almost similar fiber texture can develop from a substrate with the fiber texture of {001}||build-direction (BD). However, a substrate having the fiber {011}||BD evolves into the component {011}<100>, implying that other components of this fiber are not favored. In either case, due to the highly elongated melt-pool, the orientation {001}||hatch-direction (HD) is preferred and {011}||HD is not likely to happen.

Investigating the Reproducibility of the Wire Arc Additive Manufacturing Process

Abstract: Wire arc additive manufacturing (WAAM) of titanium parts shows promising potential for aerospace application due to its high deposition rates allowing a fast and economical production of large integral parts. However, due to the demands of aerospace industry an extensive qualification procedure is necessary to enable the parts as ready to fly. Nowadays, qualification for additive manufactured parts is a time-consuming process, so the advantages in additive manufacturing cannot be fully utilized. For this reason, a complete process qualification for WAAM would reduce the costs drastically in contrast to qualifying manufactured parts individually. As a first step the robustness and reproducibility of the energy reduced WAAM process was investigated. Thick-walled samples are manufactured layer by layer with an oscillating welding head motion. The mechanical properties of the samples are compared on an adequate statistical basis. Microstructural-and computer tomography analysis are conducted to comprehend shown interactions. The reproducibility is investigated in dependence of different heat treatment states, different directions of mechanical testing and two manufacturing systems of the same type.