System Of Zr-al-tm (co, Ni) Bulk Amorphous Alloy Composition Design And Optimization,

Amorphous alloys have attracted increasing interest due to their unique and excellent properties. However, their formation mechanism has remained unresolved. The bulk metallic glasses (BMGs) have been found only through trial-and-error methods according to some empirical rulesand quantitative criteria have been practically absent. Recently, the quasicrystal research group at Dalian University of Technology has developed composition criteria based on the correlation between quasicrystals and amorphous alloys. These rules have been proved to be validity in many alloy systems. This paper will apply the rules to the Zr-Al-TM (Co, Ni) alloy systems to find the compositions with the largest thermal stability and glass forming ability (GFA).The e/a-variant and e/a-constant lines are introduced in the Zr-Al-TM (Co, Ni) alloy system to design compositions. Samples are prepared by suction cast method. XRD, OM, SEM and TEM are used to identify the structure of these samples. BMGs with 3mm in diameter are found on the 1.5 e/a-constant line (Zr=53~61.2at%), (Zr9Co4)-Al e/a-variant line (e/a=1.25~1.5) and (Zr70.5Al29.5)-Co e/a-variant line (e/a=1.45~1.55) in the Zr-Al-Co alloy system; BMGs with the same diameter are found on the 1.5 e/a-constant line (Zr=53~63at%), (Zr9Ni4)-Al e/a-variant line (e/a=1.34~1.5) and (Zr76Ni24)-Al e/a-variant line (e/a=l.37-1.53) in the Zr-Al-Ni system.The BMGs have large thermal stabilities and GFAs after DSC and DTA experiments. On the (ZrgTM4)-Al e/a-variant line, the thermal stabilities and glass forming abilities increase with increasing e/a ratios. The Zr53Al23.5TM23.5 BMG, with the largest thermal stability and GFA, is located at the intersecting point of the (Zr9TM4)-Al e/a-variant line and 1.5 e/a-constant line. The Tg values are sensitive to the composition variations; the thermal stability and GFA have no correlation with the eutectic points.