Grain boundary sliding and rotational mechanisms of intragranular deformation at different creep stages of high-purity aluminum polycrystals at various temperatures and stresses

In the paper we show that grain boundary sliding dominates in the creep of A999 aluminum polycrystals and is accommodated by rotation modes of intragranular deformation. Accommodation mechanisms strongly depend on the applied stress a and creep temperature T. At low sigma and T, accommodation occurs by dislocation glide and mesoscale fragmentation. At high sigma and T, there appears lattice curvature, which causes the development of shear bands, multiscale fragmentation, and formation of a quasi-neck with nanosized subgrains and plastic microrotations. Noncrystallographic shears in their subboundaries propagate in local lattice curvature zones under tau(max) by the plastic distortion mechanism.