S. Mahendrakar, K. C. Chitrada, Mahatma Gandhi Institute of Technology, Hyderabad, India
Shape memory effect has fascinated the scientific community since its discovery in 1932 with their properties and scope for application. This effect basically involves the formation of thermo-elastic martensite, which can be deformed to a large extent by application of stress externally or in some cases just by cooling the sample. And the original shape can be recovered by just heating the sample. The recent years have seen the advent of a new class of shape memory alloys (SMA), which are the ferromagnetic shape memory alloys (FMSMA) and these alloys can be activated by application of magnetic field rather than varying specimen’s temperature. The FMSMA have already shown elongations of up to 10% as in Ni-Mn-Ga system compared to 8.5% shown by Ni-Ti system, they also show a fatigue limit of at least 50x 106 shape change cycles at high frequencies of working. Thus they have potential for application in Actuators involving low response time and high stroke. In this paper we have mainly focused on this particular application of FMSMA
Summary: Magnetic shape memory effect is the phenomenon by which alloys called Heusler alloys show deformation by forming martensite phase on application of magnetic field. Compared to the conventional thermally activated Shape Memory Actuators, Magnetic Shape Memory actuators have lower response time. Magnetic Shape Memory actuators have better fatigue properties of the order of 105 shape change cycles. These actuators can show a strain of 10% compared to the 8.5% in Ni-Ti shape memory alloys.
