This direction follows lattice strain, phase fraction and peak-shape changes in metals under loading, heating and ageing using neutron and high-energy synchrotron diffraction, in order to identify how deformation and phase transformation proceed.

Four parts are involved. On in-situ methods, wide-temperature (77 to 873 K) tension and loading rigs are built and the data-reduction and correction procedures for beamline conditions are established. On load partitioning, macroscopic stress is resolved to the phase and hkl grain-family level, with self-consistent models and Bayesian inversion providing phase stresses and their uncertainties. On transformation and metastable structures, diffraction criteria are established for martensitic transformation, hydride precipitation and ordering, expressed as peak-position and peak-shape evolution with temperature and composition. On linking to microstructure, lattice strain results are correlated with the deformation carriers observed by EBSD and TEM.

The approach obtains macroscopic mechanical response and phase-resolved lattice response from the same specimen, and compares how different phases and orientation families respond along one loading path.