Effects of icosahedral phase formation on the microstructure and mechanical improvement of Mg alloys: A review

Icosahedral phase (I-phase) is a relatively excellent strengthening phase in Mg alloys. Depending on their volume fraction, the yield strength of Mg-Zn-Y-Zr alloys can vary from 150 to 450 MPa at room temperature. Recently, the formation of I-phase has been considered as one of the most effective methods for developing high strength lightweight Mg alloys for automotive and aerospace applications. In this review article, a series of research work about I-phase containing Mg alloys have been systematically investigated including I-phase formation mechanism and their effects on mechanical properties of Mg alloys. Particular emphases have been given to: (1) Structure of I-phase and its orientation relationship with the alpha-Mg matrix. (2) Influence of alloying elements and solidification conditions on I-phase formation. (3) Effects of I-phase on microstructural evolution and mechanical improvement of Mg-Zn-Y-(Zr) alloys. Moreover, the applications of I-phase for the mechanical improvement of other Mg alloys such as AZ91 and super-lightweight Mg-Li alloys are also reviewed. (c) 2012 Chinese Materials Research Society. Production and hosting by Elsevier Ltd. All rights reserved.