Microstructure and martensitic transformation in Ni sub(48)Mn sub(39.5)Sn sub(12.5-x)Si sub(x) metamagnetic Heusler alloy ribbons

The paper describes the effect of Si for Sn substitution on microstructure and martensitic transformation in Ni sub(48)Mn sub(39.5)Sn sub(12.5-x)Si sub(x) (x = 0, 1, 2) Heusler alloy ribbons. The evolution of phase transformation, structure and microstructural features were examined by means of differential scanning calorimetry, analytical transmission electron microscopy and high resolution electron microscopy. The alloys were induction melted, homogenized and subsequently rapidly solidified on a rotating copper wheel. The ribbons featured a two phase structure composed of the L2 sub(1) parent phase and the martensite phase. Slight changes of the chemical composition in local areas of the studied samples were noticed. Such segregation was introduced by rapid quenching in response to different melting points of each element. This then had an effect on the local changes in the e/a ratio, effectively leading to nucleation of martensitic transformation in the affected areas.