Abstract:The electromagnetic melting and cyclic superheating method was applied to undercool the Al₇₂Ni₁₂Co₁₆ alloy melt, and a maximum undercooling, 180K was obtained. Growth morphologies were characterized by using optical microscopy, scanning electron microscope(SEM) and transmission microscopy(TEM). The microstructural morphologies indicate that a continuous growth mode of D-phase along the periodic orientation of ten-fold axis is preferred at large undercoolings. According to the Toner’s step growth mode of quasicrystal, the preferred continuous growth along the periodic orientation of ten-fold axis is caused by the loss of potential barrier for nucleating steps along this direction.

Key words:   Al₇₂Ni₁₂Co₁₆; high undercooling; decagonal quasicrystal; growth morphology