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

Abstract Preparation of cylindrical amorphous alloys with low contents of three corrosion-resistant elements, chromium, tantalum and molybdenum, were attempted by copper-mold casting. Ni–5Cr–5Ta–3Mo–16P–4B alloy of 1 mm diameter is identified as a single amorphous phase alloy and spontaneously passive in 6 and 12 M HCl, similar to the melt-spun amorphous counterpart, although high resolution TEM observation reveals the presence of nanocrystalline precipitates of about 2 nm diameter. Ni–5Cr–5Ta–5Mo–16P–4B alloy is also amorphous as shown by X-ray diffraction studies but contains nanocrystallites of about 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 other copper-mold cast Ni–16P–4B alloys with chromium, tantalum and molybdenum are composed of crystalline precipitates in the amorphous matrix.