Influence of focus offset on the microstructure of an intermetallic γ-TiAl based alloy produced by electron beam powder bed fusion

Christian Ghibaudo, Reinhold Wartbichler, G. Marchese, Helmut Clemens, Daniele Ugues, Sara Biamino

Research output: Contribution to journalArticleResearchpeer-review


It is well established in literature that, when processing intermetallic γ-TiAl components by electron beam powder bed fusion, a banded microstructure is frequently formed because of an inhomogeneous Al distribution since more pronounced evaporation of Al occurs at the top of the melt pool. This feature is particularly promoted when highly energetic process parameters (high beam currents, slow beam speeds, narrow line offsets) are used. Therefore, an approach already suggested in the literature to reduce the Al loss is to minimize the energy level of the process parameter during production. However, there is a limit to such kind of approach: minimizing the beam current or increasing the beam speed, or increasing the line offset will, at a certain point, results in not being able to achieve a completely dense material and thus some process-induced porosity, the so-called lack-of-fusion defects, starts to occur in the produced parts. In this study, the effect of an additional parameter of the electron beam powder bed fusion process is taken under consideration: the focus offset (FO), i.e. the distance between the focusing plane of the electron beam with respect to the powder bed. The effect of the FO on the residual porosity, microstructure, phase composition, hardness as well as chemical composition is investigated, thus having the possibility to demonstrate that also the FO can affect the Al loss and play a fundamental role in the generation of a homogenous microstructure, contributing to mitigate the appearance of a banded microstructure.

Original languageEnglish
Pages (from-to)132-141
Number of pages10
Journal Journal of manufacturing processes
Issue number3 March
Early online date2 Feb 2023
Publication statusPublished - 3 Mar 2023

Bibliographical note

Publisher Copyright: © 2023

Cite this