Deformation Indeuced Phase Seperation of Ni_(45)Co_5 Mn_(36.7)In_(13.3) Alloy at High Temperature

摘要

NiMnCoIn alloys are new-type magnetic shape memory alloys (MSMAs) in which a reversible magnetic-field-induced phase transformation was observed. They are ideal candidates of materials used in actuators and sensors. The polycrystalline NiMnCoIn alloys are generally brittle so that they cannot be easily deformed into the shape applicable to actuators and sensors until now. In the present paper, the influence of hot deformation on the microstructure of Ni_(45)Co_5 Mn_(36.7)In_(13.3) alloy was studied. The experimental results showed that second phase was observed after deformation at high temperature between 800-900 ℃ and at strain rate lower than 4×10~(-3)s~(-1). The content of Co of second phase was higher than the matrix alloy, while the content of In was lower than the matrix alloy. It was determined by TEM measurements as y phase with fcc structure which was popular in NiFeGa and NiMnGaCo alloys. It is possible to improve the ductility of Ni_(45)Co_5 Mn_(36.7)In_(13.3) alloy by control of amount and distribution of γ phase by hot deformation.