Formation, Time-Temperature-Transformation curves and magnetic properties of FeCoNbSiBP metallic glasses

Starting from the Fe52Co23Nb4Si5B16 alloy having good soft magnetic properties and tendency to amorphization, the addition of P, a glass former in Fe-based alloys, is explored up to 4 at.%. The alloys were rapidly solidified by means of planar flow casting and have been characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and high temperature differential thermal analysis (HT DSC). The crystallization mechanism has been studied as a function of temperature: it involves primary formation of a bcc phase at low P content and becomes eutectic at 4% P. A remarkable achievement are Time–Temperature–Transformation (TTT) diagrams for primary crystallization obtained by DSC. Magnetisation measurements as a function of temperature in parallel with thermal analysis revealed details of the crystallization sequence. The magnetic softness of alloys has been shown with hysteresis cycles. The use of P appears favourable to amorphization, thermal and magnetic properties up to 2 at.%.