Study On The Microstructures And Properties Of Pure Aluminum L2 Processed By ECAP

In order to reveal the relationships between microstructures/properties and Equal Channel Angular Pressing (ECAP) process, our efforts have focused on (a) the microstructure evolution of pure aluminum L2 with the processing of ECAP, (b) the property changing of pure aluminum L2 with the processing of ECAP. During study, optical microscope (OM) and transmission electron microscope (TEM) were used to reveal the microstructures. The tensile strength and hardness were tested at room temperature, and the damping capacity was tested by using cantilever beam technique. The main results were as follows:(1) The ultimate tensile strength of pure aluminum L2 increases with pressing times of ECAP and reaches the highest value which is increased by 95% after pressing 8 times in compare with the non-processed pure aluminum L2. The elongation percentage decreases severely from 40% to 15% after the first pressing, but it increases a little after 4 or 5 times pressing. The hardness also increases with pressing times and reaches the highest value after pressing 4 or 5times.(2) The damping capacity of pure aluminum L2 can be improved by using the procedure of ECAP. It is found that the damping capacity amounted to the maximum that is 3.7×10^-3 after pressing 4 times, and it improves about 50% compared to before pressing.(3) After ECAP and accompanying with the pressing times increasing, the initial grains of pure aluminum L2 that are equiaxed in shape and about 1mm in size transform into small equiaxed grains. The size of grains becomes about lum after pressing 10 times. It is revealed that there exists a critical grain size. It is about 1μm for pure aluminum L2 which can be reached after pressing 4 times. The grains refinement mechanism transforms from simple shear deformation resulting into grains refinement to strain accumulation resulting into grains refinement, when pressing times are more than 4 or the grains are refined to about lμm.(4) After annealing for 2 hours at 150℃, the ultimate tensile strength, yielding strength and elongation percentage of specimens of pure aluminum L2 pressed 4 times improves 9.8%,5.7% and 18.2% respectively, and at the same time the microstructures are in stable state.