日本金属学会誌

J. Japan Inst. Metals, Vol. 32, No. 10 (1968),
pp. 1019-1025

Metastable Miscibility Gap Island in Fe-Ni-Mn Ternary Martensitic Alloys

Tomoo Suzuki1

1Research Laboratory of Precision Machinery and Electronics, Tokyo Institute of Technology, Tokyo

Abstract:

On the age-hardening of the Fe-Ni-Mn martensitic alloys, the hardening mechanism of the zone formation coming from a miscibility gap was proposed, and its propriety was confirmed by thermodynamic considerations. The results obtained may be summarized as follows:
(1) The hardening rate formed C curves on the reciprocal temperature-time diagram, and its nose temperature was raised as the Ni and Mn contents were concurrently increased. This result showed the existence of a solubility limit surface in the bcc phase of ternary Fe-Ni-Mn system.
(2) Under the application of Meijering's treatment, possible combination of the energy parameters of Fe-Ni, Fe-Mn and Ni-Mn binary systems was deduced from the extent of the miscibility gap island which explained the result (1).
(3) From the equilibrium phase diagrams of Fe-Ni, Fe-Mn and Ni-Mn systems, the energy parameters for the interaction between different atoms in the bcc phase were estimated. The energy parameters of the Fe-Ni and Fe-Mn systems were nearly equal, and the Ni-Mn system showed was a larger value of negative number than them. This results satisfied the condition of (2).
(4) As the energy parameter of the Ni-Mn system had a large value of negative number, the zone rich in Ni and Mn should be ordered. It was pointed out that the ordered zone sheared by dislocations contributed to the hardening of this alloy, in addition to the hardening by the strain caused by the zone.
(5) The intense hardening response observed in the 10∼12%Ni, 5∼6%Mn alloy was interpreted in terms of the relation between the solubility line and the martensitic region.


(Received 1968/5/11)

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