Formation and Thermal Stability of Amorphous Phase in Transition Metal-Phosphorus Binary Alloys

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This paper deals with the amorphous-forming ability of Mn-P, Fe-P, Co-P, Ni-P, Cu-P, Pd-P and Pt-P binary alloys quenched rapidly from the melt and the stability and structural change of the amorphous phases on heating. A melt-quenching technique yields the formation of an amorphous phase only for Fe_<82.5>P_<17.5>, Ni_<81>P_<19>, Pd_<81>P_<19> and Pt_<80>P_<20> alloys. The critical cooling rate for the formation of an amorphous phase is calculated to be of the order 10^5-10^6 K/s for these amorphous-forming alloys from the transformation theories of crystal nucleation and growth kinetics in the liquid. Therefore, it may be stated that the binary alloys with the critical cooling rates lower than about 10^7 K/s can be melt-quenched to the amorphous state by the centrifugal quenching apparatus used in the present work. Further, it has been demonstrated that the crystallization of these amorphous phases occurs through the two stages of Am.→Am.+Crys-I→Crys-I+Crys-II→Stable Phases near the temperatures of about 620 K for Fe_<82.5>P_<17.5>, 600 K for Ni_<81>P_<19>, 535 K for Pd_<81>P_<19> and 470 K for Pt_<80>P_<20> alloy.
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