Amorphous (Al1-xMgx)82Ni8Y10 and (Al1-xMgx)81Ni12Ce7 alloys were formed in the entire x range of 0 to 1. With increasing Mg content, the exothermic peak temperature due to crystallization (Tp) and Vickers hardness number (Hv) of both alloys increase from 600 to 650 K and from 380 to 630 in the x range below about 0.5, decrease drastically to about 480 K and 220 in the vicinity of x=0.5 and remain constant in the x range of 0.5 to 1. Furthermore, the drastic decreases of Tp and Hv were found to bring about the change of brittle to ductile nature and the appearance of glass transition phenomenon. The main difference in the crystallization-induced phases between x=0.4 and 0.6 for the Al-Mg-Ni-Ce alloys is attributed to the change from Al3Mg2 + Al11Ce3 to Al12Mg17 + Mg12Ce. Accordingly, it is assumed that the drastic changes in Tp Hv glass transition behavior and ductility in the narrow x range of 0.4 to 0.6 reflect the disappearance of an icosahedral atomic configuration in the amorphous structure resulting from the Al3Mg2 compound with an icosahedral atomic configuration on a short-range scale.
(Received June 22, 1989)
Keywords: amorphous phase, alminum-magnesium-nickel-cerium alloy, alminum-magnesium-nickel-yttrium alloy, liquid quenching, thermal stability, mechanical strength, crystalliza-tion process
*Institute for Materials Research, Tohoku University, Sendai 980, Japan.
**On leave from Honda Research and Development Co., Ltd., Wako 351-01, Japan.