Grain refinement of Al–Mg–Si alloy without any mechanical deformation and matrix phase transformation via cyclic electro-pulsing treatment

In general, the grains of an AA6061 alloy cannot be refined without mechanical and heat treatments. Interestingly, in this work, the grain refinement of AA6061 alloy is successfully realized by a cyclic electropulsing treatment without any plastic deformation or matrix transformation (NP&D). In addition, unlike the gradually decreased dislocation density and homogenized evolution of crystal orientations in cyclic conventional-treated samples, in the cyclic electropulse-treated samples, the dislocation motion in {111} slipping planes is activated so that the dislocation density, the intensity of the [101]//ED texture and the distribution of the{111} planes in the sample coordinate are enhanced with an increase in the number of treatment cycles. Moreover, the strength and ductility of the AA6061 alloy are both improved through cyclic electropulsing treatment. In contrast to the cyclic conventional-treated sample, the yield strength and elongation of the optimized cyclic electropulse-treated sample are enhanced by 72.1% and 2.1%, respectively. Consequently, the electropulsing treatment can be used as a promising approach for the grain refinement of NP&D materials. This discovery also provides a theoretical supplement to the evolution of the nonequilibrium microstructure of NP&D alloys.