Peculiarities of the rheological behavior and structure formation of aluminum under deformation at near-solidus temperatures

This paper deals with a peculiar rheological behavior of aluminum at near-solidus temperatures. It has been experimentally established that there is an inverse strain rate dependence of strain resistance at temperatures ranging between 560 and 640°С and strain rates ranging from 0.06 to 1.2 s^-1. Electron backscatter diffraction analysis has shown that at temperatures ranging between 540 and 640°С and strain rates ranging from 0.06 to 0.1 s^-1, the main process of softening is dynamic polygonization, resulting in in situ recrystallization. At higher strain rates, ranging between 0.8 and 1.2 s^-1, and temperatures ranging between 560 and 640°С, the recovery is dynamic. This unusual behavior of the mechanism of softening and the presence of the inverse strain rate dependence of strain resistance can be explained by blocking the motion of free dislocations by foreign atoms, which occurs at strain rates ranging between 0.06 and 0.1 s^-1. This process results in dislocation pile-up, thereby causing in situ recrystallization. At strain rates exceeding 0.16 s^-1, there is no intensive blocking of dislocations, leading to a direct strain rate dependence of strain resistance.