The Hall–Petch relation in aluminium and its dependence on the grain boundary structure

Abstract

Mechanical properties of aluminium polycrystals exhibiting differences in grain boundary (GB) properties have been studied by means of the Hall-Petch analysis. The results obtained indicate that the value of the stress intensity coefficient k depends on the distribution of GB diffusivity. High values of the diffusion coefficients favour relaxation processes on GBs, which means lower boundary rigidity and a decrease in the value of the parameter k. Within the range of room temperatures the rigidity of GBs in aluminium is strongly dependent on temperature. On the other hand, friction stress [sgrave]_o depends on the value of the orientation factor m. It is concluded that considerable scatter of experimental results obtained by different authors studying the Hall–Petch relation in Al at room temperatures is most probably caused by the fact that the tested groups of polycrystals differed both in texture ([sgrave]_o) and in distribution of GB diffusivity (k).