Real-Time Microstructure Monitoring in Steel? Yes, It’s Now a Reality.

Just published: “Investigation of Dynamic Recrystallisation of Steel During Hot Compression Using Gleeble and Laser-Ultrasonics (GLUS)” in Metallurgical and Materials Transactions A! By Mikael Malmström, Linda Bäcke, Hans Magnusson, Johan Lönnqvist and Bevis Hutchinson.

The video shows a compression of a sample at 1050 °C, together with the real-time grain size for three of the samples in the article.

Why does this matter?

Because traditionally, observing how steel evolves under heat and pressure has meant stopping tests, cutting samples, and interpreting post-mortem snapshots. Now, a single GLUS test can yield as much information as dozens of conventional experiments – and all in real time.

What did we learn?

• During deformation, the steel undergoes dynamic recrystallisation (DRX) – a natural grain refinement process.
• If DRX finishes during compression, metadynamic recrystallisation (MDRX) follows, with little further change.
• If DRX is incomplete, static recrystallisation (SRX) takes over, leading to even finer grains.
• At high temperatures, we observe grain growth over time – but thanks to LUS, we can see when and how this happens.
• Texture? It strengthens with deformation, then softens on holding – all traceable via ultrasonic wave velocity.

The takeaway

GLUS gives us a detailed, dynamic view into steel’s internal transformation – something previously out of reach. As this technology is now also entering industrial hot strip mills, GLUS can be validated in the real industrial environment. The advantages of GLUS are especially great when studying structural steels where the microstructure is totally transformed during cooling and where the prior austenite grains are impossible to reproduce

A big thank you to our team at Swerim and collaborators SSAB for making this possible. This is a step forward not only for metallurgical science but for the future of process control in steel manufacturing.

Curious to know more? Feel free to reach out or check out the full paper ►