The influence of forging and extrusion on the microstructure and martensitic transformation in Ni-Mn-Ga alloys

The work presents the comparative analysis of the microstructure and character of martensitic transformation in Heusler Ni-Mn-Ga alloys subjected to plastic deformation by forging and complex treatment by forging with subsequent extrusion. It is shown that the treatment by forging leads to the formation of a bimodal structure with large grains of several micrometres surrounded by a fine-grained structure. After a complex treatment, a bimodal structure is also observed. But the volume fraction of the fine-grained structure is larger than in the previous case. Analysis of the martensite transformation temperature shows that thermomechanical treatment by both methods leads to a slight shift in the martensite transformation temperature to the low temperature region.