Composition-induced microcrack defect formation in the twin-wire plasma arc additive manufacturing of binary TiAl alloy: An X-ray computed tomography-based investigation

In recent years, an innovative twin-wire plasma arc additive manufacturing (TW-PAAM) process is conducted to the in situ alloying of TiAl alloys. As a newly invented method of TiAl alloy fabrication, the microcrack defect is a great concern. In the present research, two binary TiAl alloys containing different microcrack tendencies, Ti-45Al and Ti-48Al, are fabricated using the TW-PAAM method. To locate possible defects in the as-fabricated alloys, the non-destructive testing X-ray computed tomography is performed. According to the results, under the same TW-PAAM parameter set, microcracks are initiated throughout Ti-45Al while Ti-48Al stays integrated. Also, more α2-Ti3Al are generated in grain boundaries of Ti-45Al than Ti-48Al, thus lead to higher local misorientations and the intergranular microcracks. The clarification of the Al content-induced microcrack generation provides clear improvement direction of the innovative additive manufacturing technique.