Scientists at the University of Birmingham have discovered a new materials+processing approach with the potential to help engineers develop stronger, more reliable materials for two different technologies: future fusion reactors and next-generation aerospace components
The researchers have identified a mechanism called Precipitation Induced Recrystallisation (PIX), in partnership with the UK Atomic Energy Authority (UKAEA), TU Bergakademie Freiberg in Germany, and City University of Hong Kong.
This process enables metals to self-refine their internal structure through heat treatment alone, without conventional mechanical processing.
The discovery is described in two studies published in Nature Communications Materials and Scripta Materialia. The studies demonstrate PIX in a titanium-iron-molybdenum alloy relevant to aerospace applications and a tungsten-chromium alloy relevant to fusion energy systems.
In both materials, researchers discovered that tiny regions with different atomic structures form during heat treatment, but are symmetrically related. The mismatch that evolves between these regions generates internal strain strong enough to create new, smaller grains in the metal, without first rolling, forging, or mechanically deforming it.
Project leader Sandy Knowles, professor in Nuclear Materials at the University of Birmingham, said, “Our discovery challenges conventional understanding that grain refinement typically requires extensive thermomechanical processing. We show that the PIX mechanism can be used to refine grain structure in varied materials systems.
“We can design alloys where strain is generated internally during heat treatment, opening exciting possibilities for materials that are difficult to process using conventional methods, including refractory metals such as tungsten and advanced alloys for aerospace applications, particularly for net-shape manufacturing.”
Grain size is critical to material performance. Large grains provide easier paths for cracks to spread, while smaller grains create more barriers that can improve mechanical reliability and damage resistance.
Tungsten is a leading candidate material for future fusion reactors because of its heat resistance and high melting point of 3,422°C. However, it can be brittle, and radiation exposure can worsen this brittleness. PIX offers an alternative way to improve grain size in tungsten-based alloys in extreme environments.
Ageing the tungsten-chromium alloy at 1,250°C generated enough internal stress to drive recrystallisation, reducing average grain size by around 60%.
Researchers also demonstrated the same underlying principle in a titanium-iron-molybdenum ‘bcc-superalloy’, a class of material being explored for high-performance aerospace applications such as jet-engine compressor blades. Ageing the alloy at 750°C reduced the average grain size by around 90% while increasing hardness by 60 HV.
PIX may represent a wider materials-design principle that could be applied across different alloy systems, providing a new way to control grain structure and material properties through heat treatment alone. It could also be useful for materials that are brittle, difficult to shape, or produced using additive manufacturing techniques where traditional rolling and deformation processes may not be practical.
