An attempt at preparation of corrosion-resistant bulk amorphous Ni-Cr-Ta-Mo-P-B alloys

Preparation of cylindrical amorphous alloys with low contents of three corr osion-resistant elements, chromium, tantalum and molybdenum, were attempted by copper-mold casting. Ni-5Cr-5Ta-3Mo-16P-4B alloy of I mm diameter is id entified as a single amorphous phase alloy and spontaneously passive in 6 a nd 12 M I-ICI, similar to the melt-spun amorphous counterpart, although hig h resolution TEM observation reveals the presence of nanocrystalline precip itates of about 2 nm diameter. Ni-5Cr-5Ta-5Mo-16P-4B alloy is also amorphou s as shown by X-ray diffraction studies but contains nanocrystallites of ab out 5 nm diameter, the anodic current in 6 M HCl being more than one order of magnitude higher than that of the melt-spun amorphous counterpart. All o ther copper-mold cast Ni-16P-4B alloys with chromium, tantalum and molybden um are composed of crystalline precipitates in the amorphous matrix. (C) 20 00 Elsevier Science Ltd. All rights reserved.