Mg₃Cd合金における規則化

抄録

The formation of Mg₃Cd superlattice has been studied on a Mg-25.2at% Cd alloy by means of X-ray diffraction and transmission electron microscopy. Specimens were initially quenched from the disordered state, 180°C or quenched from the two phase region and then isothermally annealed at 50, 70 and 80°C.
The results obtained are as follows.
(1) The change in degree of order with the quenching temperature was measured. The critical temperature for ordering in this alloy was 155°C.
(2) The change of degree of order and domain size in specimens quenched from the disordered state were determined. The domain size determined from the X-ray diffraction method well corresponded to that from the transmission electron microscope method. The activation energy for ordering determined from the relaxation time was found to be0.87eV.
(3) When quenched from a temperature between 155°C and 140°C, broadening in the fundamental line (0002) occurred, which would result from the coexistence of the ordered and disordered phases. While, a very broadened line from the disordered phase overlapped on the superlattice line (1011) when annealed. The separation of (0002) and (1011) lines into two isolated ones arising from the ordered and disordered phases was made using the Gauss equation. The degree of order in the ordered phase was close to unity in the quenched state and little change was observed by annealing. While the degree of order in the disordered phase changed as in the case when annealed after quenching from the disordered state.
(4) When annealed after quenching from the two phase region, growth of ordered phase particles in the disordered phase was observed by means of the transmission electron microscope.