New trends in creep microstructural models for pure metals

Abstract

Various microstructural rate controlling models of creep are reviewed. They are compared to macroscopic and microscopic data for subgrain, subboundary structures and properties, and internal stress distributions. It is shown that the identification of realistic mechanisms not only requires the examination of activation parameters values, but also necessitates relevant metallographic observations. Recent data on cross slip show that this mechanism could control the creep rate of copper at intermediate temperatures while glide on prismatic planes is active in magnesium in a similar temperature range. For aluminium, subboundary migration plays an important role at intermediate temperatures, and is controlled by the glide of subboundary dislocations on (001). Glide on non compact planes inside subgrains controls the creep rate in this metal at the onset of the high temperature domain. The jog dragging screw model is particularly unrealistic. Additional data on cross slip and glide on non compact planes are needed to generalize the above models to other metals.