Peculiarities of the Rheological Behavior for the Al-Mg-Sc-Zr Alloy Under High-Temperature Deformation

The paper deals with a peculiar rheological behavior of the Al-Mg-Sc-Zr alloy at deformation temperatures of 330 and 360 A degrees C and a strain rate of 0.05 s(-1). It has been found that the strain resistance curve for this material consists of several portions. First there is material hardening, then softening, and again hardening. The application of the electron backscatter diffraction technique and transmission electron microscopy has elucidated that in-situ recrystallization is the main process of softening at the temperatures studied. The appearance of the second portion of hardening on the strain resistance curve results from inhibited in-situ recrystallization. At the deformation temperature of 330 A degrees C, as distinct from the temperature of 360 A degrees C, a small number of grains are formed on the boundaries of original grains because of insufficiently active dynamic polygonization. The presence of abounding intermetallics in the microstructure causes the development of the barrier effect of blocking free dislocations, grain and subgrain boundaries by intermetallics, thus enhancing material hardening.