Activation Energies of Crystallization in Amorphous RMn_4.5Ge_4.5Fe_1.5Al_1.5(R = La, Y, Dy) Alloys

Abstract

The effective activation energies, characteristic crystallization temperatures and enthalpies of amorphous RMn4.5Ge4.5Fe1.5Al1.5 (R = Y, La, Dy) alloys produced using melt-spinning technique were investigated by differential scanning calorimetry. X-ray diffraction measurements were performed for as-quenched and annealed samples. The crystalline structure of annealed YMn4.5Ge4.5Fe1.5Al1.5 and DyMn4.5Ge4.5Fe1.5Al1.5 alloys was determined as orthorhombic TbFe6Sn6-type with Cmcm (63) space group. The alloy with Y appears as a more useful non-magnetic analogue for DyMn4.5Ge4.5Fe1.5Al1.5 than the La-based alloy. The differential scanning calorimetry curves for Dy-and Y-based alloys also exhibit similar thermal behavior. The effective activation energies E a were determined using the Kissinger approach and high values up to 778 ± 74 kJ/mol for La-based sample were established. The comparison of Y-, La-, and Dy-based alloys suggests improvement of thermal stability with the increase in rare-earth element atomic radius in the glassy RMn 4.5 Ge 4.5 Fe 1.5 Al 1.5 systems.

Influence of Ag and Co additions on glass-forming ability, thermal and mechanical properties of Cu–Zr–Al bulk metallic glasses

“…The GFA is also reported to be connected to the activation energies of crystallization (Ea) [44][45][46]. The lower the activation energies of crystallization (Ea) are, the less stable the glass is against crystallization and thus the GFA is expected to be lower as well [44][45][46].…”

“…Co generally seems to decrease the activation energy of crystallization as well. If one assumes that a lower Ea is associated with a lower GFA [44][45][46], the alloys should become worse glass formers with increasing Ag and Co content. This conclusion, however, contradicts the trends revealed for the γ-and Kparameter (Fig.…”

“…So, the GFA does not appear to be correlated with Ea in the present alloys. The "asymmetric" phase formation on heating and cooling might be the reason for these discrepancies and contradictions [44][45][46].…”