Enhancement of static and fatigue strength of 1050 Al processed by equal-channel angular pressing using two routes

In the present investigation, annealed billets of commercially pure Al (1050) with coarse-grained microstructure of 0.6 mm were equal channel angular pressing (ECAP) processed using two routes A and B-C up to four passes. The change in the processing route results in the change of the shear plane, and consequently the change in the formed microstructure and texture. The average grain size was in the order of 1 mu m with average misorientation angle of 15 degrees after four passes of route B-C. Texture study was conducted on the shear plane for two and four-pass processed samples. A study of mechanical behavior for the ECAP specimens, using tensile and compression specimens, showed the enhanced strength with asymmetry behavior between tension and compression. Fatigue strength under load control (HCF) was also performed and the S-N curves were established as a function of number of passes and processing route. Improved fatigue strength was noticed with increasing the number of ECAP passes in harmony with the increase in tensile strength. The fractography of fatigue tested specimens was also performed and showed the formation of cleavage planes and dimples suggesting (localized) micro-plasticity at the deformation bands at the plastic zone of the crack tip. The degree of micro-plasticity increases with the applied stress amplitude. (C) 2011 Elsevier B.V. All rights reserved.