1 School of Materials Science and Engineering, Central South University, Changsha 410083, China 2 Key Laboratory of Nonferrous Metal Materials Science and Engineering(Ministry of Education), Central South University, Changsha 410083, China 3 Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China
The contribution of grain boundary sliding(GBS) and intragranular dislocation slip(IDS) in the 5A90 Al-Li alloy during superplastic deformation at 480℃ and an initial strain rate of 1×10-3s-1 was quantitatively investigated by analyzing the deformation-induced changes in the sample surface having micron grids etched by focused ion beam. As supporting evidence, scanning electron microscope and electron back scattering diffraction were used to analyze the microstructure evolution during superplastic deformation. The results show that superplasticity is the result primarily contributed by intragranular dislocation slip(about 60%-80%)in the first stage(ε < 0.65) and grain rotation is coordination mechanism, with the banded grains refined and equiaxed and the average grain size decreased(about 40%). With the increase of strain, obvious dynamic recrystallization occurs, which gives rise to the increasing grain size, and decreased effect of intragranular dislocation slip, grain boundary sliding gradually becomes the main mechanism.
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