Low temperature superplasticity of ultrafine grained Mg–9.25Zn–1.66Y alloy with an icosahedral quasicrystalline phase

• The UFG I-phase Mg-9.25Zn-1.66Y exhibited low temperature superplasticity.
• Thermal stability of the UFG microstructure was high below 473 K.
• Its thermal stability sharply decreased from 523 K.
• A criterion for achieving low temperature superplasticity was calculated.

The ultrafine grained Mg–9.25Zn–1.66Y alloy sheet with I-phase prepared by directly applying high-ratio differential speed rolling to the as-cast microstructure exhibited excellent low-temperature superplasticity (386–888% at 443–473 K) at a moderately high strain rate of 10−3 s−1. A criterion for achieving low temperature superplasticity was proposed.