INFLUENCE OF AL CONCENTRATION ON THE KINETICS OF SHORT-RANGE ORDERING IN ALPHA-CUAL

The formation of short-range order (SRO) in a concentration series of alpha-CuAl is investigated by measurement of the electrical resistivity during isochronal and isothermal annealing. An important part of the paper deals with the problem of heterogeneity versus homogeneity of SRO. It turns out that the SRO relaxation kinetics can be described as a sum of at least two independent processes, each obeying an exponential law. As an interesting fact, one of the processes reverses its sign at about 15 at% Al, so that for this concentration a single exponential behaviour results. Our interpretation is that the expansion coefficients of electrical resistivity with respect to SRO parameters of various coordination spheres change with concentration.