Abstract
The effect of cold deformation on the precipitation process in Al-1.3%Mn alloy and Al-0.5%Cr alloys was investigated kinetically by hardness, electrical resistivity measurements and transmission electron microscopy. The acceleration of precipitation by cold deformation and the retardation of recrystallization by precipitation were observed. Precipitation in the low temperature region (>450°C for Al–Mn alloy and >400°C for Al–Cr alloy), where the recrystallization process progressed gradually, was inhomogeneous; the precipitates nucleated preferentially into lattice defects, such as sub-boundaries and dislocations, were globular. In the high temperature region, the forms of the precipitates were plate in the Al–Mn alloy and flat needle in the Al–Cr alloy. The acceleration of precipitation in high temperature aging by prior cold deformation was caused by the increase in preferential nucleation sites. In low temperature aging, however, not only the increase of nucleation sites but also the enhancement of diffusion of the solute atoms during recrystallization gave rise to the acceleration of precipitation.
The addition of a small amount of Si accelerated the precipitation and made the precipitates finely distributed in both non-deformed and cold-deformed specimens. This retarded the recrystallization process further. This retardation was considered to be related to the acceleration of precipitation.
