Crystallization Kinetics of Bulk Amorphous Metallic Alloys and Its Relation to the Forgoing Relaxation Processes

Abstract

The crystallization behavior of undercooled liquid Pd₄₀Cu₃₀Ni₁₀P₂₀ metallic alloy has been studied with the aid of differential scanning calorimetry, optical metallography, and electron microscopy methods. The crystallization occurs as a single-stage process starting preferably on the surface of casting voids in the sample volume and on the outer sample cutting planes. The linear crystal growth velocity of crystallizing cells was measured at several constant temperatures in the range of 590–620 K. It is constant at constant temperatures and its temperature dependence is in good agreement with the theoretical concepts of Uhlmann calculated using the temperature dependence of the experimentally determined viscosity temperature dependence of the alloy studied. Differential scanning calorimetry study of isothermal overall volume transformation kinetics of samples pre-annealed at 600 K for 600 s has been also carried out at several constant temperatures. The experimental data are interpreted on the basis of the equation of Kolmogorov–Avrami–Johnson–Mehl for the case of 3D growth of fixed number of preexisting nuclei. The possibility to re-vitrify the crystallized samples by their melting in differential scanning calorimeter, followed by quick cooling with cooling rate of 5 K s⁻¹ is shown. The volume transformation kinetics of re-vitrified samples has been also studied.