Strengthening effects of icosahedral phase in magnesium alloys

Abstract

Microstructure and strength of two alloys Mg₉₅Zn_4.2Y_0.8 and Mg_92.5Zn_6.5Y containing icosahedral phase have been studied after extrusion at 250°C and 400°C. Due to its high symmetry and quasiperiodicity, the icosahedral phase can form strong interfaces with the matrix in various orientations. The icosahedral phase particles have a strong pinning effect on the grain boundaries that stabilizes grain size. They are resistant to coarsening, and remain hard at higher temperatures, imparting good strength with ductility at 200°C. Very few deformation structures such as high dislocation density and twins are observed after extrusion or tensile tests. c-type dislocations are commonly observed, which has important implications for greater ductility. Due to the stability of microstructure, various post-extrusion treatments are possible.

Acknowledgements

This work is partly supported by Japan Science and Technology Corporation.