Effect of pulse current on microstructure of 6061T6 aluminum alloy in flow friction extrusion forming
The effects of pulse current on the formability of 6061T6 aluminum alloy in flow friction extrusion forming were studied by ap-plying pulse current in the flow friction extrusion process.Meanwhile,the effect laws of pulse current on the microstructure evolution in deformation zone were studied by means of EBSD and TEM.The results show that the pulse current reduces the deformation resistance and improves the fluidity of the material.Under the conditions of downward speed of 0.6 mm·min-1,rotational speed of 950 r·min-1 and re-duction of 3 mm,the flow friction extrusion forming height of 60614T6 aluminum alloy can be increased from 15 mm to 20 mm by applying 3800 A pulse current.The application of pulse current promotes the recrystallization during deformation process,refines the microstructure of different deformation zones,and increases the proportion of large angle grain boundaries in the deformation zone.After flow friction ex-trusion forming,there are a large number of linear dislocations,network dislocations and dislocation walls formed by dislocation climbing.After applying pulse current,large plastic deformation occurs,the grains are broken and nanocrystallines are formed in material under the composite effect of stirring force and extrusion force.
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