Investigation of Martensitic Phase Transformation and Magnetic Properties of Fe-30%Ni-2.6wt%Mo-X%Co Alloys

Abstract

In this study, the microstructure of thermal effective martensitic phase transformation observed in the Fe-30wt.%Ni-2.6wt.%Mo-Xwt.%Co (X = 0.8, 1.8) alloy was investigated morphologically and crystallographically by using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). In SEM studies, it was observed that the morphology of the martensite phase changed from lath and lenticular structure to massive structure with the addition of Co to the alloy. In addition to this, nano martensite formation was also observed as another effect of Co addition (figure 2c, d). Properties of lenticular martensite, electron diffraction pattern of austenite and martensite structures were given by TEM studies. According to the Differential Scanning Calorimetry (DSC) analysis, it was determined that the martensitic transformation temperature (Ms) significantly increased with the increase of the Co amount in the alloys. Also, by using Mössbauer spectroscopy, it was shown that the amount of martensite increased with the increase of Co amount and the magnetic order of the alloy changed accordingly.