Characterisation and structure development of Ni64Cu9Fe8P19 glass forming alloy at elevated temperatures

Nickel-copper-iron-phosphorus Ni64Cu9Fe8P19 alloy was prepared using 99.95 wt.% Ni, 99.95 wt.% Cu, 99.95 wt.% Fe and the Ni-P master alloy. The precursors were melted in the arc furnace under argon gettered protective atmosphere. Then the alloy was induction melted in quartz tubes under vacuum (10−2 bar) and quenched in water to obtain ingot of 10 mm diameter. The primary microstructure of the ingot was investigated by the use of light microscope. The Ni64Cu9Fe8P19 alloy was cast using melt spinning. The ribbon in the as cast state was characterised with use of transmission electron microscope (TEM) and X-ray diffraction (XRD). Differential thermal analysis (DTA) of the melt-spun ribbon was made to determine the thermal stability and glass forming ability of the alloy. The pieces of ribbon were heated to different temperatures and annealed during 1 h then characterised with use of the Mössbauer spectroscopy and the X-ray diffraction to see the change of the microstructure after heating to elevated temperatures. It has been found that the devitrification sequence consists of progressive formation of the (Ni, Fe, Cu)3P phase and (Ni, Fe, Cu)-FCC phase. The temperature range of the sequence is determined under isochronal conditions.