2010 Volume 51 Issue 7 Pages 1178-1182
In this study, effects of Al addition on the glass-forming ability, phase evolution, and structural variation of Zr50−xCu50Alx (x=0∼25) alloys are investigated by means of X-ray diffraction and scanning electron microscopy. The phase type and structure of the Zr-Cu-Al alloys strongly depend on the Al content. The main phases of the Zr45Cu50Al5 alloy are CuZr and icosahedral phase when the casting size is between 5 mm and 10 mm, but change to CuZr + glassy phase when the casting diameter is decreased to 3 mm. The intensity and number of Bragg peaks corresponding to the icosahedral phase in the Zr45Cu50Al5 alloy decrease quickly as the cooling rate increases, and finally, only a diffuse peak is seen. These results suggest that there is strong correlation between the icosahedral phase and the glassy phase in the Zr-Cu-Al alloys during rapid solidification. The structure of the glassy phase in the Zr-Cu-Al alloys shows icosahedral short-range ordering. The icosahedron with five-fold symmetry is incompatible with lattice periodicity, which presents a barrier to crystallization and improves the glassy formability.