Two experimental techniques which were based upon load relaxation and creep were proposed in order to account for the dislocation structural changes which occurred during the transient experiments that were used for the measurement of activation volumes. Both techniques were modelled within the framework of thermal activation, while assuming that the variation in the internal stress was proportional to that in the plastic strain and that the density of mobile dislocations was an exponential function of the effective stress. The results which were obtained here for -Al47Al51Mn2 polycrystals entirely justified these assumptions. It was shown that each individual technique permitted the measurement of the effective activation volume, and of a correction factor which accounted for structural changes. Combination of the present results permitted independent estimation of the changes in internal stress and mobile dislocation density. A comparison of the activation volumes which were indicated by using the 2 techniques immediately revealed whether the mobile dislocation density varied during tests. The agreement which was found between the values of the strain-hardening coefficients suggested that the structural changes were identical during transient tests and constant strain-rate tests.

J.Bonneville, B.Viguier, P.Spätig: Scripta Materialia, 1997, 36[3], 275-81