# Kinetic and geometric characteristics of martensitic transformation in iron-nickel-manganese alloy

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## Conclusions

- 1.
Methods were worked out and a study was made of the effect of temperature and degree of transformation on the nucleation rate and size of martensite crystals.

- 2.
It was demonstrated that the temperature dependence of the nucleation rate can be described by a curve with a maximum, while the absolute value of the nucleation raten declines continuously and progressively as the degree of transformation is increased, and becomes zero by the time the transformation is complete. A variation of this kind inn is evidently due to the dislocational nature of the martensite transformation (as shown indirectly byK=10

^{9}and by direct experiment on the formation of a relief among the dislocations brought to light by pre-etching). Equations are put forward for relatingn andK to the degree of transformation. - 3.
It was shown that the activation energy of martensite crystal nucleation is not a function of temperature or the degree of transformation, and is equal to about 930 cal/g. at. The work of nucleation for martensite crystalsA

_{n}is not a function of the degree of transformation, but is almost halved when the temperature of the isotherm drops from 4670 (at.−50°C) to 2360 cal/g.at. (at.−155°C). - 4.It is suggested that the nucleation rate of martensite crystals is a function of the temperature and degree (time) of transformation as follows$$\begin{gathered} n = K_0 \left[ {1 - \left( {\frac{V}{{V_{\max } }}} \right)^3 } \right] \cdot e^{ - \frac{U}{{RT}}} \times \hfill \\ \times e^{ - \frac{{A_3 }}{{RT}}} \hfill \\ \end{gathered} $$
- 5.
It has been shown that the thickness, length and volume of the martensite crystals are virtually unaffected by temperature, but are determined exclusively by the degree of transformation. By the end of the transformation, the reduction in the thickness and length of the martensite plates is 15–18%, which is due to variation in the state and reduction in the volume of unchanged austenite.

### Keywords

Activation Energy Austenite Martensite Martensite Transformation Geometric Characteristic## Preview

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### References

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