Prediction of good glass forming ability in amorphous soft magnetic alloys by thermocalc simulation with experimental validation

Abstract

Alloys in a (Fe70Ni30)80(B–Si–Nb)20 system, with good glass forming ability (GFA), were identified using Thermocalc software to simulate liquidus temperatures (T's) and solidification ranges (areas between the liquidus and solidus in a binary phase diagram,a line at fixed T). A region with excellent GFA was identified at 14–18% B and 0–7% Si with the balance Nb, showing minima in liquidus and solidification range. A region with a solidification range minimum, but no corresponding liquidus minimum was identified at 3–8% B and 5–10% Si but had lower GFA. A shallow liquidus minimum, with no minimum in solidification range, at 3–5% B and 1–3% Si had the lowest GFA and did not produce amorphous material. Measured GFA was ranked using parameters Trg, ΔTxg, and γm, defined herein. Only the reduced glass transition temperature, Trg, was predictive for the alloys. Differential Scanning Calorimetry (DSC) data showed liquidus T's to agree. Curie temperatures, Tc's were observed to increase with B/Nb ratio. Simulations of liquidus and solidification range for alloys with 18 and 15% glass formers do not show regions with minima in both, indicating good GFA is not expected.