Magnetostrictive Alfenol Whisker Sensor Performance and Sensitivity to Whisker Thickness

In this paper, we investigate the influence of sheet thickness on abnormal grain growth and texture development in NbC-added Fe 80 Al 20 alloys (Alfenol) that are being used as sensors. Being able to reduce sensor thickness is found to be an important for parameter for avoiding work-hardening as the sensors deflect. The alloy is rolled to form sheets with a thickness of 0.2, 0.35, and 0.5 mm, and then annealed to develop a 〈100〉 preferred orientation along the longitudinal direction. Whisker-like ribbons of alloy are then cut from the textured sheet with widths of 2, 4 and 6 mm and the performance of cantilevered whiskers evaluated for future use as flow sensors. The net voltage changes in the Hall sensor that converts magnetization change to electrical signal output were proportional to the applied tip force when the 0.2 and 0.35 mm thick whiskers were bent, a trend that was not observed beyond a low tip deflection in the 0.5 mm thick whisker. Of particular interest is that the 0.2 mm thick whisker shows good flexibility to withstand severe bending, whereas plastic deformation occurred in the 0.35 mm thick whisker, resulting in fatigue induced fracture/failure due to work hardening of the material after frequent severe bending.