Efeito da adição de Fe nas propriedades microestruturais, magnéticas e térmicas de ligas CuAlMn

Abstract

Ferromagnetic Shape Memory Alloys (FSMAs) are intelligent materials that combine shape memory properties with ferromagnetic behavior, returning to a predetermined shape when subjected to thermal or magnetic stimuli. The chemical composition and thermal treatments are crucial for their magnetic and structural properties. This work analyzes the partial substitution of Cu by Fe in CuAlMn alloys, investigating its influence on magnetic, thermal, and mechanical properties. To this end, CuAlMn and CuAlMnFex (x=1.5 and 3.0 at.%) alloys were prepared and analyzed. The microstructural characterization was performed using EDS, XRD, and OM; the magnetic properties were evaluated using VSM, and the thermal characterization was carried out using DTA, with hardness measured by Vickers microhardness (MH). The results showed that all the alloys exhibited L21+DO3 phases at room temperature. The addition of Fe increased the lattice parameter in the homogenized and quenched alloys. Regarding magnetic properties, the homogenized samples exhibited more intense magnetic properties than the quenched samples, and the addition of Fe decreased remanence, coercivity, and saturation magnetization in the homogenized samples while increasing coercivity in the quenched ones. Comparative analysis between homogenized and quenched alloys revealed that the quench process did not eliminate any phase transformation in the samples. Both quenchig and the addition of Fe promoted a reduction in the enthalpy of the L21 + DO3 → L21(p) reaction. Alloys with higher Fe content exhibited higher fusion enthalpies. Additionally, the increase in Fe content in the alloys strongly correlated with a greater percentage reduction in hardness after quenching. In conclusion, the analyses conducted indicate that both the addition of Fe and the applied heat treatments have the potential to significantly alter the microstructural, magnetic, and thermal properties of CuAlMn alloys.