Structure development in Co38Ni33Al29 ferromagnetic shape memory alloy

In the present study, a set of the directionally solidified samples from ferromagnetic shape memory alloy with the nominal composition Co38Ni33Al29 was prepared using the Bridgman method. It is shown that various growth rates result in various solidification structures of the crystals, mainly in different ratios of the disordered phase gamma - cobalt solid solution and the ordered phase beta -B2 (Co,Ni)Al. This ratio has the fundamental effect on the temperature of the martensitic phase transition. The results are compared with the structure of samples prepared by the floating zone method. The structures of samples prepared with the different growth rate were studied by metallography, SEM, EDX, and EBSD methods. The samples without high-angle grain boundaries were cut from the prepared crystals for the mechanical testing.