The recrystallization behavior of shear band in room temperature ECAPed Al-Mg-Mn-Sc-Zr alloy

The Al-6 Mg-0.4Mn-0.25Sc-0.1Zr extrusion rod was subjected to ECAP for 1 pass at room temperature to get the nonuniform structure. Then, the samples were annealed under 100 ?C, 150 ?C, 200 ?C, 250 ?C, 300 ?C, 350 ?C, 400 ?C, 450 ?C, 500 ?C and 550 ?C for 1 h. It is found that the 1P ECAP induces an extremely concentration of shearing strain. There are two areas in the 1P sample: shear band and non-sheared zone. In the shear band, the hardness is 147 HV and, in the non-sheared zone, the hardness is only 120 HV. Meanwhile, the hardness of the original rod (0P sample) without ECAP is 110 HV. After the annealing, the hardness decreases but the hardness of the 1P sample decreases much faster than that of the 0P sample, leading to the hardness ?upside down? phenomenon. Also, in the 1P sample, the hardness of the shear band decreases much faster than that of the nonsheared zone. The tensile test has proved this phenomenon too. After annealed at 500 ?C, the Al3(Sc, Zr) particles in the shear band is large and some are incoherent with the matrix, while in the non-sheared zone, the particles are still coherent and only a part of them have grown up. These phenomena are attributed to the drastic recrystallization induced by the high strain in the shear band.