Microstructure characterization of LAE442 magnesium alloy processed by extrusion and ECAP

• Combined extrusion and equal channel angular pressing results in significant grain refinement by factor 1000 approximately.
• Al11RE3, Al2Ca and Al10RE2Mn7 secondary phases are present in the as-cast material while Li was dissolved in the Mg matrix.
• Extrusion and ECAP have no effect on the composition of the secondary phases but they influence strongly their distribution.
• Texture evolution is affected by decrease of c/a ratio due to the presence of Li and resulting activation of non-basal slip.

The magnesium alloy LAE442 was processed by extrusion and equal channel angular pressing (ECAP) to achieve ultrafine grained microstructure. Detailed characterization of the microstructure was performed by scanning electron microscope, electron back scattered diffraction (EBSD) and transmission electron microscope. The initial, as-cast, microstructure consisted of large grains of ~ 1 mm. The grain refinement due to the processing by severe plastic deformation led to a decrease of the average grain size to ~ 1.7 μm after the final step of ECAP. A detailed characterization of secondary phases showed the precipitation of Al11RE3, Al2Ca and Al10RE2Mn7 intermetallic phases. X-ray diffraction measurements proved that Li is dissolved within the magnesium matrix in the as-cast condition. Newly formed Al3Li phase was observed after ECAP. The texture formation due to the extrusion and ECAP was different from that in the other magnesium alloys due to the activation of non-basal slip systems as a result of the decrease of the c/a ratio.

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