Calorimetric effects during the α → γ transformation in Fe-Ni-Ti metastable alloys

A calorimetric study of the reverse α → γ transformation has been carried out in five metastable Fe-Ni-Ti alloys. The amount of the α phase in the initial samples is more than 50%. The exothermic processes of the decomposition of the α and γ phases exceed the endothermic reactions of formation of the reverted austenite upon heating to the midpoint of the temperature interval of the reverse α → γ transformation. In the middle part of the interval in which the maximum rate of the transformation is recorded by the magnetometric method, the calorimetric curve does not exhibit thermal effects. This disagreement indicates the complex character of the transformation. At the finishing stage of the α → γ transformation, there is clearly detected an endothermic reaction.