ALLOYS OF HIGH GLASS-FORMING ABILITY

A series of Zr-Ti-Al-Cu-Ni alloys, e.g., Zr57Tl5Al10Cu20Ni8, were foun d to have high glass-forming ability (GFA). Cylindrical bulk amorphous samples with diameters of 10 mm were produced by casting the melts in a copper mould. The Zr65Cu17.5Ni10Al7.5 alloy, which was reported to have the highest GFA heretofore, was found to be amorphous only in the surface with radius dimensions of less than 1 mm under the same cooli ng conditions. The alloys were also cast in a chevron-shaped copper mo uld to compare the GFA of the alloys. Ti and Al were found to be the c ritical components favorable to the GFA of the Zr-Ti-Al-Cu-Ni alloys, which could greatly reduce the crystal growth rate of the alloys. Cu a nd Ni appeared to be the less critical components. However, it was nec essary to modify the contents of all the components according to their effects in order to design an alloy of high GFA. The amorphous alloys displayed very high strength, thermal stability and superplasticity a t elevated temperature.