Diffraction methods for the characterisation of defects in intermetallic compounds

Different intermetallic compounds were ball-milled to introduce several defects and promote the order-disorder transition. The degree of disorder and the defects introduced were investigated on powder samples of NiAl, Ni3Al and FeAl by means of X-ray and neutron diffraction at room and higher temperatures. A total pattern fitting procedure based on the Rietveld method is proposed to analyse the data in order to characterise the crystal structure defects introduced by the ball-milling process. In particular, the theory of Warren [1] on antiphase domains, twin and stacking faults has been successfully applied. Point defect concentrations were correlated to the lattice parameter changes as measured by the fitting procedure. Reordering during annealing was also followed with the same approach.