Magnetic and mechanical properties of polycrystalline galfenol

The Zone Melt Crystal Growth Method (FSZM) has been used to produce polycrystalline Galfenol specimens, Fe81.6Ga18.4, with preferred {100} orientation. This crystal growth technique has advantages over conventional Bridgman methods in that zone rates used were at least an order of magnitude greater; 350 mm/hr versus 2-4 mm/hr. This material had measured magnetostrictions ranging from 168 ppm to 220 ppm compared to 290 ppm for a single crystal with a similar composition. It was discovered that upon machining a large increase in magnetostriction occurred, similar to15%. Using Orientation Imaging Microscopy (OIM) techniques it was shown that the magnetostriction increase is due to the removal of off-axis gains located on the circumference of the FSZM samples. The room temperature mechanical properties were measured to be 72.4 GPa-86.3 GPa modulus of elasticity, 348 MPa-370 MPa ultimate strength, and elongation values of 0.81%-1.2% depending upon zoning conditions.