Magnesium alloys for high performance structural components in automotive industry

Magnesium as the lightest structural metal has a great potential for major use in the automotive industry. However, unfavorable properties such as corrosion, flammability, poor cold workability and cost restrict applications to low volume or “niche” automotive production. High pressure die castings of specialty Mg alloys such as Mg-Al-RE or Mg-RE-Zn alloys (RE – rare earth elements) provide excellent combination of elevated temperature strength at low-weight with potential to substitute common Al-Si casting grades. Twin roll casting in combination with superplastic forming is on the other hand raising potential of sheet material with sufficient hot formability and low cost of manufacturing. It has been observed that if hot deformation is applied on as-twin-roll-cast material (AZ91, WE43) continuous dynamic recrystallization of initial coarse dendritic as-cast microstructure is taking place. Strain rate sensitivity of AZ91alloy increased with increasing level of strain from 0.20 to 0.33 allowing more uniform deformation without necking