Pure single-phase samples, with a low O concentration, were investigated as a function of the Al content. The structural state was characterized by performing residual electrical resistivity measurements. In the case of samples which contained 50 to 54.5at%Al, reversible resistivity variations were detected during heat treatment at increasing and decreasing temperatures between 820 and 1020K (for the stoichiometric alloy). These variations were suggested to be consistent with small changes in the degree of long-range order. Two main conclusions concerning atomic mobility in these alloys were deduced from the variations. One was that the atomic mobility was composition-dependent and increased significantly as the deviation from stoichiometry increased (at higher Al contents). The other was that, when compared with stoichiometric Ni3Al, the atomic mobility was lower in the present compound.

C.Dimitrov, N.Martin, H.Fekkar, O.Dimitrov: Scripta Materialia, 1996, 34[9], 1405-9