Magnetomechanical testing machine for ferromagnetic shape-memory alloys

Recently, a new class of active materials, known as ferromagnetic shape-memory alloys, has shown promise as actuator and sensor materials. These alloys, such as Ni2MnGa and Fe3Pd, are ferromagnetic and undergo a reversible diffusionless structural phase transformation giving rise to shape-memory behavior. In order to explore the behavior of these materials it is necessary to combine both mechanical materials testing, magnetic field application, and magnetization measurements. To accomplish this, an apparatus called a magnetomechanical testing machine (MMTM) has been constructed. The MMTM combines a screw driven mechanical load frame with a dual-dipole electromagnet to load specimens both mechanically and magnetically. The pair of magnets allows the magnetic field to point in any direction in the plane containing the uniaxial loading axis of the mechanical test frame. In addition, the specimen temperature is controlled and the surface is observed microscopically. This apparatus is described and some preliminary measurements are reported. Saturation magnetization measurements for Fe3Pd made with the MMTM are found to be within 2% of previously reported values.