Modelling the microstructural mechanisms of change in engineering alloys at sub-zero temperatures

In manufacturing, automotive and aerospace applications, cryogenic treatments are used to improve strength, fatigue and wear resistance of structural and hard wearing engineering alloys. The proposed research will produce experimentally validated computational models of microstructural changes in such alloys at sub-zero and cryogenic temperatures, using cryogenic treatments of selected steels as a case study. Models will be validated using advanced materials characterisation techniques, as well as through mechanical testing.

The kinetics for microstructural change are reduced at cryogenic temperatures and yet, phase transformations and precipitation of secondary phases occur. This must be due to displacive transformations and mechanically driven transport mechanisms. Deformation (by differential thermal contraction) drives the generation of dislocations but may also drive localised phase transformations. Thermodynamic solubility also changes with temperature. It is the coupling between deformation, transport and thermodynamic stability that is the focus of the study.