Martensitic Transformation and Shape Memory Effect of NiCoMnSn High Temperature Shape Memory Alloy

Since a large magnetic-field-induced shape recovery strain is observed, NiCoMnSn alloy has become an important member of metamagnetic shape memory alloys (MMSMAs). Compared with other MMSMAs such as NiCoMnIn, NiCoMnSn has the advantage of low cost. Although some scientists have carried out the investigations on magnetic field induced reverse transformation, microstructure and magnetic property in NiCoMnSn alloys. The study of transformation behavior at high temperature is seldom reported.

In present paper, a series of NiCoMnSn alloys are prepared by arc melting. The phase transformation and microstructure are studied by DSC, optical microscope and XRD. Shape memory effect (SME) at high temperature is measured using compression test.

It is found that the composition has a remarkable effect on the phase transformation and microstructure of NiCoMnSn alloys. By changing the composition, some NiCoMnSn alloys exhibit thermal elastic martensitic transformation at high temperature. The maximum martensitic transformation starting temperature is higher than 280 °C. The largest shape recovery strain upon heating is about 3% and the recovery ratio decreases linearly with the increase of prestrain. The results suggest that NiCoMnSn alloy with a certain composition is a promising high temperature shape memory alloy.

Keywords:  shape memory alloy, martensitic transformation, shape memory effect, high temperature