Microstructural evolution during the annealing of an extruded AZ31 magnesium alloy

Microstructural evolution during the annealing of AZ31 extruded rod at 400 °C has been examined by employing neutron diffraction and electron backscatter diffraction (EBSD). In the as-extruded bar, equiaxed grains smaller than 5 μm and large elongated grains having significant degrees of internal misorientation are oriented mainly with <1 0 1¯ 0> parallel to the extrusion direction. Rapid grain growth occurs within the 180 s annealing period at 400 °C at the expense of the small grains with the internal orientation gradient as driving force. After short time annealing, small equiaxed grains are formed inside the large elongated grains, and grains having <1 1 2¯ 0> parallel to the extrusion direction show preferred growth. As a result, a transition of the main texture component to the <1 1 2¯ 0> component occurs after annealing for 1800 s at 400 °C.

Research highlightsThe manuscript presents an experimental investigation on the microstructure and texture development during a post-extrusion heat treatment of an AZ31 alloy, by using neutron as well as electron diffraction techniques. The results show clearly the texture changes from the <10.0> fibre to the <11.0> fibre component with grain growth and the role of internal misorientation as an important driving force for the grain growth. The preferred growth of the grains having the <11.0> fibre component leads to a transition of the main texture component to the corresponding global texture.