Augmentation of Fatigue and Tensile Strength of AA-6061 Processed through Equal Channel Angular Pressing

Abstract

ECAP (Equal Channel Angular Pressing) is a technique used to enhance the strength of material by grain refinement. In this research, an aerospace grade aluminum alloy-6061 is investigated. The specimens were pressed through ECAP die channels, intersecting each other at an angle of 90oC where a shear plane of 45oC was developed, that results grains refinement. Fatigue strengths and CGR (Crack Growth Rate) for the stress ratio R 0.7 and 0.1 are found and compared with the as-received material.It was observed that the CGR is slower at stress ratio R=0.1, as compared to stress ration R=0.7. An electric furnace was embedded with ECAP die to regulate the material flow through this die. The temperature of the die was maintained at 450oC during ECAP pressing and the specimens were also preheated at this temperature using another furnace. The ECAP die consists of two channels intersecting at 90o provided with safe inner and outer corner radius to avoid scaling.The microstructural observations revealed that the deformation was perfectly plastic. The ECAPed and as-received materials were also characterized by tensile tests, micro-hardness tests, and 3-point bend fatigue tests.