Grain refinement in as cast Al–Mg–Mn alloy during high temperature equal channel angular pressing

Author: Ning J. L.   Jiang D. M.   Fan J. Z.   Zuo T.   Zhang Q.   Xu J.  

Publisher: Maney Publishing

ISSN: 1743-2847

Source: Materials Science and Technology, Vol.25, Iss.7, 2009-07, pp. : 820-828

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

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Abstract

An as cast Al–Mg–Mn alloy with coarse equiaxed grain structure was processed by equal channel angular pressing (ECAP) at 350°C up to eight passes. Systematic studies were made on the microstructural evolution during ECAP by optical microscopy, electron backscattered diffraction and TEM. Equal channel angular pressing led to a considerable grain refinement, resulting in an average cell size of about 1 μm and a fraction of high angle boundaries of 75% after eight pressing passes. Deformation bands were not developed during the ECAP process, and a reasonably equiaxed substructure was obtained even after one pass. The main mechanism of grain refinement was attributed to the continuous dynamic recrystallisation based on the motion of deformation induced dislocations. Discontinuous recrystallisation at grain boundaries and triple junctions also contributed to the refinement, which played an important role especially at high strain of eight passes.