Influence of microstructure in the martensitic transformation and in the physical and magnetic properties in metamagnetic shape memory alloys

In this work we have focused in the study of the influence of the microstructure in metamagnetic shape memory alloys (Ni-Mn-In and Ni-Mn-Sn systems) together with the effect of Co-doping, in order to gain insight into these effects and to control and improve the properties of these materials. Starting with the ternary Ni-Mn-Sn system, we have stablished the correlation between microstructural parameters and magnetostructural properties in these alloys. We have characterized the different microstructural states induced by thermo-mechanical treatments and correlated them with the properties of the alloys. The cobalt-doped quaternary system, Ni-Co-Mn-Sn-Co has been the next subject of study. With the aim of obtaining further understanding of the effect of Cobalt doping the magnetic coupling, we have selected the Ni-Mn-In system as case study. Since in the systematic study of the effect of milling we have observed that long milling times lead to amorphous states, we have extended our study to the recrystallization processes in Ni-Co-Mn-Sn and Ni-Co-Mn-In alloys, with the analysis of the evolution of the different phases, the cell parameters and microstrutural parameters as grain size, micro and macrostrains.