Using photothermal radiometry to enable real-time sintering density measurements

Electronic Field Assisted Sintering (EFAS) is an advanced manufacturing technique that uses high electrical currents to transform a metallic or ceramic powder into a solid piece. This process rapidly induces high temperatures throughout the sample, resulting in a faster and more efficient sintering process.

One of the biggest challenges when implementing this method is determining when the correct density has been reached. Currently, density information cannot be acquired in situ, so manufacturers must test many samples in a trial-and-error approach. Hua et al. developed a method to measure sample density using photothermal radiometry, potentially enabling in situ measurements.

“It is a very big deal since this technology is supposed to be fast and efficient,” said author Zilong Hua. “But if you have to keep performing trial-and-error measurements, then you cannot consider it an efficient technology anymore.”

The team leveraged a well-known relationship between microstructure features and thermal diffusivity. Photothermal radiometry can measure localized diffusivity in real time without any surface treatment, providing a means of obtaining in situ density information. In tests, their technique produced accurate density data and identified local anomalies resulting from improper mixing or tooling imperfections.

The team’s goal in this preliminary work was to demonstrate their method’s efficacy. In subsequent studies, they plan to fully realize the potential of photothermal radiometry.

“We want to develop an instrument which can be inserted into the EFAS system,” said Hua. “From there, we can do real-time measurements. We are planning to finish it within the next 12 to 15 months.”

Source: “Microstructure characterization of electric field assisted sintering (EFAS) sintered metallic and ceramic materials using local thermal diffusivity measurement,” by Zilong Hua, Patrick Adam Merighe, Jorgen Rufner, Arin Preston, Robert S. Schley, Yuzhou Wang, Spencer Doran, and David Howard Hurley, AIP Advances (2023). The article can be accessed at https://doi.org/10.1063/5.0160625 .