Dependence of Thermal Stability of Ultra Fine Grained Metals on Grain Size

High pressure torsion (HPT) is a technique based on severe plastic deformation (see [1] for review). The initial coarse-grained sample is deformed by torsion and simultaneously by high pressure of several GPa is applied. Ultra fine grained (UFG) metals with grain size around 100 nm can be produced by HPT. The mean grain size of HPT prepared sample depends on material and parameters of the deformation. Different grain size can be obtained, e.g. by varying the applied hydrostatic pressure.