Role of Grain Boundary Movements on the Creep Rate Sensitivities in Aluminium

Tests to determine the effects of temperature and stress on the steady state creep rate in 99.5% Al showed that the applied stress sensitivity parameter increases at an acceleratng rate with increasing stress and less so with increasing temperature. The activation energy for creep is in the range of the activation enthalpy of lattice self-diffusion and decreases with increasing temperature. Recovery during creep is controlled by dislocation climb at barriers. Gliding of dislocation on slip planes is controlled by stress. These are responsible for subboundary formation. At high stresses, these effects almost disappear. The absorption of dislocations at grain boundaries increases grain boundary segregation and leads to increased grain boundary sliding with increasing stress. 18 ref.--AA(UK/US).