The local configurations of point defects were detected, with atomic-scale resolution, in mechanically-milled samples. This was done, via the nuclear quadrupole interactions which they induced at neighboring sites of 111In probe atoms, by using the perturbed angular correlation of -rays technique. In the case of PdIn, signals were detected which could be attributed to Pd vacancies, Pd antisite atoms and In vacancies. In addition, a new signal was observed which was attributed to high-energy In antisite atom defects which were next to In probes. The concentrations of Pd vacancies and In antisite atoms were deduced from the measured site fractions, and were monitored as a function of the milling time. Milling in WC under Ar led to a Pd vacancy concentration that increased from zero, and saturated at a value of 3.5at% after 0.5h. These large vacancy concentrations made a contribution, to the stored excess enthalpy, of about 4.4kJ/mol. The In antisite atom concentration reached a value of about 4at% after 2h of milling. This provided evidence for a gradual disordering of the B2 structure. The spectra for NiAl exhibited higher vacancy-site fractions that were attributed to binding with the impurity In probes.

G.S.Collins, P.Sinha: Materials Science Forum, 1996, 225-227, 275-80