Evaluation of microstructure and superplasticity in friction stir processed 5083 Al alloy

摘要

Friction stir processing (FSP) has been developed as a potential grain refinement technique. In the current study, a commercial 5083 Al alloy was friction stir processed with three combinations of FSP parameters. Fine-grained microstructures with average grain sizes of 3.5-8.5 mu m were obtained. Tensile tests revealed that the maximum utility of 590 percent was achieved at a strain rate of 3 X 10~(-3) s~(-1) and 530 deg C in the 6.5-mu m grain size FSP material, whereas for the material with 8.5-mu m grain size, maximum utility of 575 percent was achieved at a strain rate of 3 X 10~(-4) s~(-1)and 490 deg C. The deformation mechanisms for both the materials were grain boundary sliding (m approx 0.5). However, the 3.5- mu m grain size material showed maximum utility of 315 percent at 10~(-2) s~(-1) and 430 deg C. The flow mechanism was solute-drag dislocation glide (m approx 0.33). This study indicated that establishing a processing window is crucial for obtaining optimized micro structure for optimum superplasticity.