The Influence of Friction on the Processing of Ultrafine-Grained/Nanostructured Materials by Equal-Channel Angular Pressing

The influence of friction on the mechanical properties, physical properties, and microstructure of the processed billets by equal-channel angular pressing (ECAP) was investigated in this work. Selecting the lubricants from different available lubricants which were the agents to change the friction in the process was based on the ring compression test. Simple tensile tests showed that ductility was improved more than 16%, which was accompanied with almost constant yield strength and ultimate strength by increasing the friction coefficient. In addition, about 4.6% more impact energy was absorbed in the impact test. Microhardness values were recorded on the longitudinal and cross-sectional planes of each billet to evaluate the degree of the homogeneity of the mechanical properties. The results obtained from microhardness measurement confirmed that there was a little enhancement in the homogeneity of the work-piece on its longitudinal plane by increasing the friction. However, the homogeneity of the work-piece on its cross-sectional plane decreased by increasing the friction coefficient. Assessment of the microstructure of different samples showed considerable influence of the ECAP process on the elimination of pores and cavities in the billets. In addition, density measurements indicated that the size of the pores within the bulk material was decreased as the friction was increased.