Use of quantitative metallography in the evaluation of hydrogen action during martensitic transformations

Experiments based on image analysis method and electrochemical potentiostatic tests were performed with particular attention to the influence of hydrogen on the stabilisation of austenite of Fe–32 wt.%Ni alloy. This alloy exhibits great hydrogen absorption capacity (25 wt. ppm) and this presence modifies the martensitic transformation essentially at temperatures near MS (−40°C). In the whole range of the quenching temperatures, the difference between the volume fraction of martensite, measured on specimens with hydrogen or without hydrogen, is constant. It was found that the value of the interfacial area of the martensite plate groups SV is the best parameter describing the interfacial area between martensite and austenite. It was also found that there is a general relationship, expressed by a linear function, between this morphological parameter and an anodic current I.