Mechanical Properties of Magnesium Alloy AZ31 after Severe Plastic Deformation

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Abstract
Grain refinement of magnesium alloy AZ31 was studied in multidirectional forging (MDF) under decreasing temperature conditions. MDF was carried out up to large cumulative strains of 5.6 with changing the loading direction during decrease in temperature from pass to pass. MDF can accelerate the uniform development of very fine- grained structures and an increase of the plastic workability at low temperatures. New grain structures with the minimal grain size of 0.23 μm can be developed by continuous dynamic recrystallization at a final processing temperature of 403 K. As a result, the multidirectional- forged alloy showed excellent higher strength as well as moderate ductility at room temperature, and also a superplastic elongation of over 300% at 423 K. The mechanisms of strain-induced and fine-grained structure development and of the excellent plastic deformation are discussed in detail.