Decomposition of La- and Dy-rich amorphous alloys

An Al25La50Ni25 and newly discovered Al38Dy50Ni12, Al38Dy50Co12 and Al41Dy47Ni6Co6 glasses prepared by melt-spinning were studied by means of electrical resistance (ER) and calorimetric measurements at constant and at linearly increasing temperatures as well as by X-ray diffraction (XRD) and microhardness studies after different heat treatments. Changes in short-range order during relaxation lead to prepeaks in XRD spectra, ER and hardness increases. The glass transitions are accompanied by endothermal heat effects and ER drops. In Al25La50Ni25, crystallisation sets in above 240 °C via the formation of metastable LaNi and AlLa3 phases which may transform into La(Ni, Al). The Al38Dy50Ni12 glass crystallises only above 400 °C; fine precipitates of Dy3Ni and probably DyAl appear before a Dy(Ni, Al) phase forms. The Co-containing materials possess still increased stability but are very brittle.