Thermal Stability and Microstructural Evolution in Ultrafine-Grained Nickel after Equal-Channel Angular Pressing (ECAP)

摘要

Processing through the application of severe plastic deformation (SPD) is an attractive procedure for refining the microstructure of a metal to the submicrometer or nanometer level without the introduction of any contamination or porosity. The two primary techniques of SPD processing are high-pressure torsion (HPT) and equal-channel angular pressing (ECAP).~[1,2] Recent reports have described the microstructural evolution occurring in materials subjected to ECAP~[3-6] and HPT~[7] and they reveal that the mean grain size introduced by processing and the presence of microstructural homogeneity are dependant upon the material and the precise processing parameters. In practice, any successful application of these two procedures for commercial purposes will depend critically upon the subsequent thermal stability of the ultrafine-grained microstructures after SPD processing. Earlier reports have described microstructural evolution and thermal stability in Cu~[8] and Ni~[8,9] processed by HPT, and the present investigation was initiated to provide similar information for Ni processed by ECAP.