Frank-Kasper phase in Al-Mg-Zn icosahedral quasicrystal alloys

Frank-Kasper phase, with an icosahedral close-packed structure, Mg₃₂(Al, Zn)₁₉, is considered as the 1/1 approximant phase analogous to its icosahedral quasicrystal. The morphologies of Frank-Kasper phase in Al_xMg₄₀Zn_60-x (x = 20-45, mole fraction) alloys subjected to normal solidification were studied by using optical microscope, X-ray diffraction and scanning electronic microscope. The microstructure and composition of Frank-Kasper phase were determined. It is found that, single Frank-Kasper phase can be obtained in Al_xMg₄₀Zn_60-x (x = 20-45) alloys, independent of the exact Al content; whereas the morphology of Frank-Kasper phase transforms from petal-like to the cross with increasing Al content.