In situ X-ray imaging of hot cracking and porosity during LPBF of Al-2139 with TiB2 additions and varied process parameters

Laser powder bed fusion (LPBF) additive manufacturing of 2XXX series Al alloys could be used for low volume specialist aerospace components, however, such alloys exhibit hot cracking susceptibility that can lead to component failure. In this study, we show two approaches to suppress the formation of hot cracks by controlling solidification behaviour using: (1) TiB2 additions; and (2) optimisation of LPBF process parameters. Using high-speed synchrotron X-ray radiography, we monitored LPBF of Al-2139 in situ, with and without TiB2 under a range of process conditions. In situ X-ray radiography results captured the crack growth over 1.0 ms at a rate of ca. 110 mm s-1, as well as pore evolution, wetting behaviour and build height. High-resolution synchrotron X-ray computed tomography (sCT) was used to measure the volume fraction of defects, e.g. hydrogen pores and microcracks, in the as-built LPBF samples. Our results show adding TiB2 in Al-2139 reduces the volume of cracks by up to 79 % under a volume energy density of 1000 to 5000 J mm �3, as well as reducing the average length, breadth, and surface area of cracks. & COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In this study, two approaches, including TiB2 additions and optimization of LPBF process parameters, were used to suppress the formation of hot cracks in laser powder bed fusion (LPBF) additive manufacturing of 2XXX series Al alloys. High-speed synchrotron X-ray radiography and high-resolution synchrotron X-ray computed tomography (sCT) were used to monitor the LPBF process and measure the volume fraction of defects in the as-built samples. The results showed that adding TiB2 in Al-2139 reduced the volume of cracks by up to 79% and decreased the average length, breadth, and surface area of cracks.