Irreversible enthalpy relaxation of amorphous (Fe1−xNix)83P17(x=0–1) alloys

Abstract

This paper deals with the changes in exothermic enthalpy relaxation behaviour and Curie temperature of amorphous Fe33Ni50P17 alloy upon annealing, and the compositional effect (i.e. the change with Fe/Ni ratio) on the magnitude of exothermic reactions during continuous heating of (Fe1−xNix)83P17 (x=0–1) alloys, in order to clarify the thermal relaxation behaviour with irreversibility of metal-metalloid type amorphous alloys. For Fe33Ni50P17 alloy, the exothermic reaction showed two distinctive peaks at about 480 and 580 K and the low-temperature peak had a very strong correlation with the change in Curie temperature. Furthermore it was observed that for (Fe1−xNix)83P17 alloys the magnitude of the low-temperature peak was nearly proportional to the number of Fe-Ni atom pairs. However, the high-temperature one was almost independent of the changes in Curie temperature and the ratio of Fe to Ni. These results suggest that the exothermic enthalpy relaxation peak at temperatures far below Tg (or Tx) originates from the local rearrangement of metal-metal interactions of different species, while the high-temperature peak is due to the rearrangement of metal-metalloid bonding. This separation into two stages is interpreted as due to the difference of bonding forces between metal-metal and metal-metalloid pairs in amorphous Fe-Ni-P alloys.