Superplastic characteristics and forming of LZ91 Mg-Li alloy sheet

Magnesium-lithium (Mg-Li) alloys, due to their high specific strength, have great potential in the modern aviation industry. The superplastic characteristics, microstructure evolution, mechanical properties, and forming process of LZ91 Mg-Li alloys at 200°C–300°C were studied in this paper. Tensile tests show that the optimal elongation of tensile specimens is 812.6% at 300°C under a strain rate of 5 × 10⁻⁴s⁻¹. The flow stress of the material increases with strain during the high-temperature tensile testing due to the grain coarsening. Meanwhile, low dislocation densities were observed during tension, which is not sufficient for dynamic recrystallisation to occur. The finite element method is used to investigate the forming schemes of a narrow-mouth box component. Finally, this component was manufactured by the powder pressure bulging process at 300°C experimentally.