Mechanical properties of fine grain 5083 aluminum alloy

Microstructure and mechanical properties of friction stir processed (FSP) 5083-H321 aluminum was studied and compared to that of the parent material. Grain size of the base material was about 20 mum compared to the grain size of 3 mum in the FSP area. Hardness measurements showed a reduction in strength in the FSP area. Tension and compression tests show a reduction of the yield stress in the FSP area. This is in contradiction to the Hall-Patch effect and emphasizes that using the grain size without considering its dislocation density can not accurately predict its yield strength. Shear strength of the FSP area is less than the base material and is in line with the lower hardness reading of that area. Elongation is improved in the FSP area with no degradation of the Ultimate tensile strength. Fatigue life of the FSP area is lower than the parent material due to the faster crack initiation.