Correlation between microstructure and thermal dilation behavior of amorphous Fe-Co-Zr-Mo-W-B alloys

The microstructures and thermal properties of Fe61Co9−xZr8Mo5WxB17 (x = 0 and 2) formed under different vacuum conditions were investigated by scanning electron microscopy(SEM), X-ray diffractometry(XRD), transmission electron microscopy(TEM), and conventional dilatometry(DIL). The variation of the non-monotonic effects of tungsten content and vacuum conditions on the glass forming ability(GFA) of Fe-based alloys can be drawn in a schematic diagram. The higher the GFA of alloys, the higher the difference between the thermal expansion coefficients of glassy state and crystalline state(Δα), which can be described by the free volume model during dilatometric measurements. Under low and high vacuum conditions, the viscosity and microhardness are improved and the fragility of the Fe-based alloys are decreased by adding tungsten.