Magnetic and Mechanical Properties of Hybrid Magnetic Material Systems from Hipped Al with Ferromagnetic Particles

Abstract Ferromagnetic alloys exhibit the Villari effect, whereby applied stress changes their magnetization and permeability, making them intrinsically load-sensitive. These stress-dependent magnetic properties enable sensing via magnetic excitation and readout. Compared with strain gauges, ferromagnetic alloys can offer high sensitivity, a broad load range, robustness in harsh environments, low cost and low-maintenance structural health monitoring. In the present study, a hybrid material system consisting of an Al base material and ferromagnetic particles of Co, Ni, and pre-oxidized Fe is realized by high isostatic pressing. The magnetic properties are then characterized using harmonic analysis of the eddy current signals, both under no load and under load during tensile tests. Analysis of the third harmonic showed that the Al composite with pre-oxidized iron exhibited the most pronounced magnetic properties. Generally, the composites exhibit different signal amplitudes under tensile stress, depending on the added ferromagnetic material. The amplitude of the third harmonic of aluminum with pre-oxidized iron vs. elongation shows a clear inflection point. This demonstrates the potential of this composite material for use as a sensor material. Adding ferromagnetic particles to aluminum increases the yield strength. Analysis of the fracture surfaces shows that the fracture behavior is related to the intermetallic phases formed with Al. When using pre-oxidized iron, the detachment of particles from the matrix is the dominant mechanism of damage.