Effect of Mo–Fe substitution on glass forming ability and thermal stability of Fe–C–B–Mo–Cr–W bulk amorphous alloys

Amorphous Fe67−xC10B9Mo7+xCr4W3 (x = 1–7 at.%) plates with 0.64 mm thickness were prepared by copper mold casting. The thermal properties and microstructural development during heat treatments were investigated by a combination of differential scanning calorimetry, differential thermal analysis, and X-ray diffraction. The glass forming ability (GFA) and activation energy for crystallization have a distinct dependence on Mo content. Fe62C10B9Mo12Cr4W3 was the best glass former in this study, demonstrating a supercooled liquid region, ΔTx = 51 K, and an activation energy for crystallization, Q = 453 kJ/mol. The GFA of alloys in this system was governed by elastic strain optimization resulting directly from the variation in Mo content. Heat treatments were performed to demonstrate resistance to crystallization under typical processing conditions. Alloys in this system exhibited a three phased evolution during crystallization. A second set of heat treatments was performed to identify each phase. An analysis of phase evolution revealed a distinct dependence of phase evolution with stepwise substitution of Mo for Fe in this system.