Martensitic transformation in Fe-Mn-(Si,Ge,Sn) alloys

Effect of Ge and Sn on the martensitic transformation and shape memory effect in Fe-Mn(22-26at.%)-Si alloys is investigated by the substitution of Si by Ge or Sn from 1.5% to 6at. %. It was found that addition of Ge causes the transformation to perform in several steps. Substitution of Sn makes this effect more superior. Resistometry, calorimetric and dilatometer measurements reveal that one of the transformation stages is c lose to second order. It is characterized by small values of the thermal hysteresis and heat effect. Shape memory effect measurements have shown that only one of the transformations has a distinct shear nature. At the same time the relief typical for martensitic transformation was observed by optical microscopy. The nature of both stages of transformation is discussed.