Influence of Microstructure Instability on Creep Behaviour of UFG Pure Materials

Experiments were conducted to determine an effect of creep temperature on creep behaviour of pure Cu. The ECAP pressing was performed at room temperature by route Bc. Constant load creep tests in tension were conducted at 373-573 K under different stresses. The values of the stress exponent n of the minimum creep rate for ultrafine-grained (UFG) and coarse-grained material were determined. Microstructure of samples was characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with the electron backscatter unit (EBSD). The microstructure analyses showed that microstructure of pure Cu processed by 8 ECAP passes and subsequent creep exposure contained large fraction of boundaries with coincidence sites lattice (CSL). The results showed that creep in UFG materials is influenced by additional creep mechanisms up to 0.5 Tm when the UFG microstructure in more or less stable