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The slow transition from an out-of-equilibrium glass towards a supercooled liquid is a complex relaxation phenomenon. In this Letter, we study the correlation between mechanical relaxation and equilibration kinetics in a Pd20Pt20Cu20Ni20P20 high-entropy metallic glass. The evolution of stress relaxation with aging time was obtained with an unprecedented detail, allowing us to pinpoint new interesting features. The long structural relaxation towards equilibrium contains a wide distribution of activation energies, instead of being just associated to the ß relaxation as commonly accepted. The stress relaxation time can be correlated with the equilibration rate and we observe a decrease of microstructural heterogeneity which contrasts with an increase of dynamic heterogeneity. These results significantly enhance our insight of the interplay between relaxation dynamics and thermodynamics in metallic glasses., Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnolo­gies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminant, Postprint (author's final draft)

Due to the disordered structure of amorphous alloys, the complex structural dynamics involves the particle rearrangements with a large span in time and size scales. The characterization and mechanism of structural dynamics of amorphous alloys are crucial and fundamental for the further research of relaxation behavior and physical aging kinetics of glasses. Abundant researches show that the relaxation spectra of rare-earth-based amorphous alloys, which are represented by lanthanum- and cerium-based alloys, show obvious secondary relaxation process, and the system becomes an ideal carrier to investigate the relationship between structural dynamics and mechanical properties of amorphous alloys. In this review, the anelasticity of metallic glasses was discussed. The anelastic deformation, as the main component of deformation, can totally recovery after unloading in creep experiments, and its mechanism is important to form deep understanding about the structural dynamics of metallic glasses. Additionally, the main characteristics of anelastic deformation during creep and creep recovery were summarized, and some theoretical models for quantitative and qualitative description were introduced., Postprint (author's final draft)

Structural study of compounds containing aluminum, cobalt, and varying amounts of cerium and lanthanum. Use of differential scanning calorimetry (DSC) and non-crystalline diffraction (NCD)., Estudio de la estructura de compuestos que contienen aluminio, cobalto y diferentes cantidades de cerio y lantano. Uso de calorimetría de barrido diferencial (DSC) y difracción no cristalina (NCD)., Estudi de l'estructura de compostos que contenen alumini, cobalt i diferents quantitats de ceri i lantani. Ús de calorimetria d'escombrat diferencial (DSC) i difracció no cristal·lina (NCD).

Lacking the structural information of crystalline solids, the origin of the relaxation dynamics of metallic glasses is unclear. Here, we report the evolution of stress relaxation of high-entropy metallic glasses with distinct ß relaxation behavior. The fraction of liquidlike zones, determined at each temperature by the intensity of stress decay, is shown to be directly related to both the aging process and the spectrum of relaxation modes obtained by mechanical spectroscopy. The results shed light on the intrinsic correlation between the static and dynamic mechanical response in high-entropy and conventional metallic glasses, pointing toward a sluggish diffusion high-entropy effect in the liquid dynamics., Postprint (author's final draft)

The power-law relationship between creep rate decay and time is one of the intrinsic characteristics of metallic glasses. In the current work, a La30Ce30Ni10Al20Co10 high-entropy metallic glass was selected as the model alloy to test the influences of physical aging and cyclic loading on the power-law creep mechanism, which was probed by the dynamic mechanical analysis in terms of the stochastic activation, and contiguous interplay and permeation of shear transformation zones. It is demonstrated that a notable discrepancy appears between thermal treatment and mechanical treatment on the power-law creep mechanism of this high-entropy metallic glass. On the one hand, physical aging below the glass transition temperature introduces the annihilation of potential shear transformation zones which contribute to creep. On the other hand, cyclic loading can tailor the “forward” jump operations competing with the “backward” ones of shear transformation zones by controlling the interval time (recovery time). The current research offers a new pathway towards understanding the creep mechanism of high-entropy metallic glasses., Postprint (author's final draft)

High temperature deformation was probed in a La-based high entropy metallic glass with an evident slow ß relaxation. The correlation between high configurational entropy and high temperature deformation mechanism was analyzed. On the one hand, by increasing the strain rate, the degree of deviation from Newtonian behavior in high entropy metallic glasses is lower than that of conventional metallic glasses, which is ascribed to the high configurational entropy. On the other hand, high configurational entropy leads to a decrease in activation volume in high temperature deformation of metallic glasses. Identifying the influence of high configurational entropy on the deformation mechanism paves the way for further understanding of the mechanical behavior of metallic glasses., Postprint (author's final draft)

The viscoelastic properties of Pd20Pt20Cu20Ni20P20 high-entropy metallic glass were probed by dynamic mechanical spectroscopy and stress relaxation. The experimental evolution of stress can be characterized by the empirical Kohlrausch-Williams-Watts function during the tensile stress relaxation measurement. We develop a linear relaxation model able to describe the whole process of stress relaxation in a wide range of temperatures. The linear relaxation model takes into account the microstructural heterogeneity of the glass, and thus its dynamical heterogeneity, so that the thermal effect and stress-driven process are physically decoupled. The activation energy spectra at various temperatures reveal the changes of the deformation units during stress relaxation, which is the result of the interplay between stress and temperature. This study decomposes the widespread hierarchical dynamics due to structural heterogeneity which accommodates the viscoelastic deformation of the high-entropy metallic glasses., Postprint (author's final draft)

Dynamic mechanical relaxation is a fundamental tool to understand the mechanical and physical properties of viscoelastic materials like glasses. Mechanical spectroscopy shows that the high-entropy bulk metallic glass (La30Ce30Ni10Al20Co10) exhibits a distinct ß-relaxation feature. In the present research, dynamic mechanical analysis and thermal creep were performed using this bulk metallic glass material at a temperature domain around the ß relaxation. The components of total strain, including ideal elastic strain, anelastic strain, and viscous-plastic strain, were analyzed based on the model of shear transformation zones (STZs). The stochastic activation of STZ contributes to the anelastic strain. When the temperature or external stress is high enough or the timescale is long enough, the interaction between STZs induces viscous-plastic strain. When all the spectrum of STZs is activated, the quasi-steady-state creep is achieved., Postprint (author's final draft)