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Microstructure Evolution of Magnesium Alloy AZ31in Deformation Zone by Heavy Reduction Rolling

Author: SunKeMing
Tutor: HuXiaoDong
School: Liaoning University of Science and Technology
Course: Materials Processing Engineering
Keywords: AZ31magnesium alloy twin deformation zone annealing grain orientation
CLC: TG339
Type: Master's thesis
Year: 2013
Downloads: 54
Quote: 0
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Abstract


Magnesium is the least dense of all metals being used in practice for structuralApplications, which has much advantage, and are increasing applied progressively inautomobile industries，communication and consumer electronic. therefore it is widelyaccepted that magnesium alloy is" the green engineering metals of the21stcentury".But magnesium alloy has a hexagonal close-packed （hcp） crystal structure withlimited number of operative slip systems at room temperature. Magnesium alloy haslow plasticity at room temperature. Therefore most wrought magnesium Products aremanufactured by multi-pass small-reduction rolling at present. But the cost is high.And the application of magnesium alloys is limited. So how to increase the plasticityof magnesium becomes an important research direction.The material used in this research was made by directional solidification of AZ31magnesium alloy. The as-cast AZ31magnesium was rolled by one pass50%reductionrate at400℃. Microstructures and textures at different deformation and annealingconditions were investigated by optical microscopy （OM） and scan electronmicroscopy （SEM） as well as EBSD. Stresses and strains distribution in deformationzone were simulated by FEM. The results of the study are as follows:（1） Twinning and slipping are two deformation mechanisms for magnesium alloy.The role of twinning was increased with the increasing of deformation. Themorphology of twins gradually changed from parallel, bending, and intersection.Original coarse grains were cut and refined to small grains by different twinningsystems with high-angle grain boundary even after annealing.（2） Annealing temperature, holding time and deformation degree are importantfactors to recrystallization. At annealing temperature350℃, annealing time20minutes and rolling reduction about50%. The yield strength σ0.2 of plates is139.6MPa. The tensile strength σb is227.2MPa. The ductility property is19.9%.（3） The magnesium alloy plate is conducted by solid solution. There is strong （0001）cardinal annealing twins in non-deformation zone. Grains present obvious preferredorientation. Grain has not obvious preferred orientation with the increase ofdeformation in the rolling deformation zone.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal pressure processing > Rolling > Non-ferrous metal rolling
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