✍ Scribed by K.P. Singh; J.G. Park
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M,. These observations are in conflict with the contention that P:' = Pa' at n/r,?, and that the mnrtensitic reaction occurs at a temperature where AF)'"" = 0.
(4) In iron-nickel alloys containing 29-33 per cent, nickel, it has been demonstrat,ed(ll) t-hat, the y -+ CC' reaction can be induced by deformat,ion at t,emperat;\mes up to 200°C (corresponding to an energy difference of about 250 cal/mole) above M,T. Inasmuch as the Singh-Parr hypothesis suggests that y is more stable than CC' at temperat'ures above M,?, one would not expect, the conversion of stable y into w&able Q'.
(5) Finally it should be emphasized t,hat, the thermodyna,mic calculations of free-energy and enthalpy difFerences discussed in connection with t,he t,hermodynamics of martensnic transformat,ions have been confirmed by direct calorimetric measurements for the case of iron-nickel martensitjes. (13,14) In view of this evidence. we must conclude tha't the hypothesis that, M, represents the temperature at, which the austenitic and mart,ensitic phases have equal free energies cannot, be sustained. S. V. BA~CI,IFFE~ ~Munlabs, In,c:
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