Diffraction-line shifts and broadenings in continuously and discontinuously coarsening precipitate-matrix systems: coarsening of initially coherent nitride precipitates in a ferrite matrix

The initial precipitation of misfitting particles can be accompanied by elastic accommodation of the precipitate/matrix misfit leading to considerable matrix lattice dilatation/contraction and variable lattice microstrain. In this stage, the entire assembly of matrix and precipitate particles, as a whole, can diffract coherently. Upon aging of the system, relaxation of the accommodated misfit can occur by continuous and/or discontinuous coarsening of the precipitates. These processes are associated with distinctly different, characteristic diffraction phenomena, also involving a transition from coherent to incoherent diffraction of precipitates and matrix. For the case of, initially fully coherent, alloying element nitrides in a homogeneously nitrided ferrite matrix, these effects have been identified and analyzed, thus allowing tracing of misfit-relaxation processes.