Anomalous temperature dependence of Young's modulus in Fe73Ga27 alloys

Elastic modulus of magnetic materials tends to increase with temperature rising, as the result of gradual loss of magnetic order with approaching Curie point. In this work, the similar behavior was also observed in the directional solidified Fe73Ga27 alloy along the <100> preferred orientation. However, unlike the previous theory, results of magnetic-temperature and thermal expansion measurements show the absence of magneto-volume effect. Such unusual behavior of Young's modulus could be attributed to the enrichment of diffusing atoms along the direction of lowest modulus during the phase transition of A2 → D03. According to the analysis of in situ heating XRD and TEM, the structure transitions of A2 → D03 → A1 → L12 were identified in the temperature range 20-500 °C, which correspond exactly to the changes of Young's modulus in both as-cast and directional solidified samples.