X-ray diffraction data informs metal additive manufacturing method

Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning of a high-powered laser over a thin bed of metallic powder to create a single layer, which may then be built upon to form larger structures. Most melting, resolidification, and subsequent cooling take place at higher rates and with higher thermal gradients than in traditional metallurgical processes, with much of this occurring below the surface.

A team of LLNL, SLAC National Accelerator Laboratory, and Ames Laboratory scientists recently demonstrated the use of in situ x-ray diffraction to monitor the subsurface structural evolution of the crystalline phases in a titanium alloy as it cools below the solidification temperature to the β-transus following laser melting. The resulting paper, published in Nature Scientific Reports, shows how such data can be used to extract instantaneous bulk cooling rates of the resolidified material for the regime between resolidification and solid-state transformation to the α-phase. According to the team, these insights are crucial for formulating a sound theoretical underpinning of the LPBF process in general and understanding how the properties of additively manufactured titanium components can be predicted.

Another paper from the same LLNL–SLAC research collaboration on mitigation of LPBF manufacturing defects entitled “Dynamics of pore formation during laser powder bed fusion additive manufacturing” was recently featured by the journal Nature Communications as part of a special showcase of 2019 material science and metallurgy article content.

[V. Thampy, A.Y. Fong, N.P. Calta, J. Wang, A.A. Martin, P.J. Depond, A.M. Kiss, G. Guss, Q. Xing, R.T. Ott, A. van Buuren, M.F. Toney, J.N. Weker, M.J. Kramer, M.J. Matthews, C.J. Tassone, and K.H. Stone, Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing, Scientific Reports 10, 1981 (2020), doi: 10.1038/s41598-020-58598-z.
A.A. Martin, N.P. Calta, S.A. Khairallah, J. Wang, P.J. Depond, A.Y. Fong, V. Thampy, G.M. Guss, A.M. Kiss, K.H. Stone, C.J. Tassone, J.N. Weker, M.F. Toney, T. van Buuren, and M.J. Matthews, Dynamics of pore formation during laser powder bed fusion additive manufacturing, Nature Communications 10, 1987 (2019); doi: 10.1038/s41467-019-10009-2.]