Materials Science Forum Vol. 1197

Abstract: In this paper, the effect of grain size of metastable D0₃ and D0₁₉ phases in rapidly cooled Fe-27at.%Ga alloy on their transition to equilibrium L1₂ phase at instant heating is studied using temperature dependent internal friction with additional support of neutron diffraction and SEM-EBSD methods. Using two alloys with a similar chemical composition, we demonstrated for the first time that a decrease in the grain size of metastable D0₃ phase, which was achieved by annealing at different temperatures followed by subsequent water quenching, leads to a faster transition to equilibrium state, i.e. that the D0₃ to L1₂ transition takes place at a lower temperature. The D0₁₉ to L1₂ transition takes place at a significantly higher temperature exhibiting better stability of overcooled D0₁₉ with respect to the D0₃ phase.

Abstract: The development of structural-functional integrated materials with high damping capacity and thermal stability is essential for aerospace and precision engineering applications. This study investigates NiTiHf/Nb shape memory alloys with nanowire-like and spherical Nb phases through heat treatments at various temperatures to assess the impact of Nb phase morphology on damping behavior. Compared to the alloy with nanowire Nb phase, the alloy with spherical Nb phase demonstrates higher transformation temperatures, a narrower thermal hysteresis with △T decreasing from 78 K to 66 K, and an internal friction value ~125% higher in the martensitic state, while maintaining a wide operating temperature range of up to 400 K. These results indicate that the alloy with spherical Nb phases exhibits improved transformation reversibility and a promoted damping response. The frequency-dependent internal friction response and transmission electron microscopy observations further suggest that the enhanced damping capacity is attributed to the combined effects of interface-related dislocation activity and martensitic twin-boundary motion. These findings underscore the significance of controlling Nb phase morphology as an effective interface-engineering strategy for the design of advanced high-damping shape memory alloys.

Abstract: In this paper, transient effects due to different diffusion-controlled phase (in Fe-Ga alloys) and structural (in Al and Cu alloys) transitions are collected and analyzed. In contrast with well-known transient anelasticity due to diffusionless (martensitic) transitions, transient anelasticity for diffusion-controlled transformations has got much less attention in the literature, most probably due to its weaker effects compared with the sharp transient peaks found in martensitic transitions. In this paper, we consider two types of materials and two types of transient anelasticity. The first group of anelastic effects (transient internal friction peaks) that are analyzed in this paper is associated with reversible and irreversible phase transitions in polymorphic Fe-Ga alloys (bcc-, fcc-and hcp-derived structures: D0₃ → L1₂ → D0₁₉ → B2/A2), and the second one – by recrystallization (internal friction ‘pseudo’ peaks) in several mainly non-ferrous Al-and Cu-based alloys without polymorphic transitions. It is demonstrated that the main features of existing approaches for transient anelasticity due to martensitic transitions can also be applied to anelastic effects in diffusion-controlled transitions, while quantitative values in these models are significantly different from those for shear transition as they are dependent on diffusion processes.

Abstract: Internal friction and Young’s modulus were measured for pure iron and a high carbon steel. Temperature dependent measurements in pure iron show a strain dependent component to internal friction below the Curie temperature. It can be attributed to the magneto-mechanical damping as confirmed by amplitude dependent measurements at room temperature with and without magnetic field. The bcc to fcc phase transition on further heating is clearly marked by internal friction peaks in both iron and steel. The effects of cementite dissolution and precipitation in steel are visible on thermal cycling at even higher temperatures.

Abstract: Mechanical spectroscopy tests of high-purity nickel single crystal with different lattice orientations (100), (110) and (111), were performed in a forced oscillation pendulum, under high vacuum (10⁻⁶ – 10⁻⁵ mbar), at different frequencies. The temperature was varied from room temperature up to 500 °C. The present study focuses on the understanding of the dislocation dynamics responsible for deformation, and their kinetics. The effect of the different crystal lattice orientation is also studied. A general overview of the internal friction (IF) spectrum reveals three mechanical loss peaks, for all the three orientations, namely P0 (transient peak), P1 and P2. P1 an P2 might be related to a motion of dislocations controlled by the migration of jogs of screw and edge type. Activation energies of around 1.5 – 2 eV were found for both the P1 and P2 peaks. These activation energies are comparable to pipe diffusion (1.94 eV) and grain boundary diffusion (1.3 – 2 eV) in nickel. Dislocation pinned in jogs might act as grain boundaries, enhancing the diffusion of vacancy (lower activation energy compared to Ni self-diffusion (2.88 eV)). TEM analyses were performed in parallel and confirmed the presence of dislocation jogs and the absence of sub-grain boundaries and twins. The experiments have demonstrated that mechanical spectroscopy is a powerful tool to better understand the basic dynamics of dislocations in nickel single crystals.

Abstract: Closed-cell aluminum foam is the type of foam where its pores, or "cells," are closed, forming a pocket of air or a bubble. Closed-cell aluminum foam is used in different fields, such as aerospace, structural, railway, shipbuilding, and many others. This is due to its lightweight, sound and vibration absorption properties, excellent heat insulation, non-combustibility, environmental friendliness, mechanical damping, and many other beneficial properties [1]. A closed-cell aluminum foam contains air pockets or bubbles, which makes it challenging to build its 3D and 2D geometric models for further studies like Finite Element Analysis and other non-destructive experimentation, i.e., numerical modelling [2],[3]. This study focuses on the numerical and geometric modelling of the closed-cell aluminum foam. There has been a rising need for more research on how to model the closed-cell aluminum foam so that it can be studied and expanded in its application [3]. Several studies have shown how to model closed-cell aluminum foam using different modelling techniques, such as cell structure and shape [4], [5]. This study aims to conduct a parametric modelling of the closed-cell aluminum foam using the CT (Computed Tomography) images of the foam to reconstruct 3D models using Materialise Mimics V26 software and Matics V18(its twin). The reconstruction will be conducted by varying different parameters, like segmentation and other mesh-processing parameters, to develop models. The geometric properties of these models will be compared to the actual measured geometric properties to determine which set of parameters gives the accurate model. Also, to determine how the reconstruction steps affect the geometry of the models.

Abstract: Rare Earth Elements (REEs) and Noble Metals (NMs) are critical resources in modern technologies, including electronics, renewable energy systems, and advanced materials. Even though REEs are moderately abundant in the Earth’s crust, their inhomogeneous distribution and difficult extraction procedures represent serious technical and environmental challenges. The increasing demand for these materials and the environmental problems associated with their primary extraction have led to an intensive search for sustainable recovery methods from secondary sources, such as contaminated biomass, electronic waste (e-waste), and mining residues. This overview article provides a critical analysis of the literature on the enrichment and recovery of REEs and NMs from secondary sources, with a special focus on thermal treatment technologies, including combustion, pyrolysis, and gasification. These technologies transform waste materials into solid residues enriched in valuable metals, which can be extracted more efficiently. The existing recovery methods are presented in terms of efficiency, environmental friendliness, and economic viability, and the main knowledge gaps are also discussed.

Abstract: In this work, new solid electrolyte Li_1+xAl_xTi_2-x-yTa_y(PO₄)₃ (x = 0.3; y = 0.04) was prepared by solid state method at sintering temperature of 900 °C for 6 hours. The prepared material was characterised by thermogravimetric analysis, X-ray powder diffraction, fourier transform infrared spectroscopy and scanning electron microscopy. The ionic conductivity was investigated by impedance spectroscopy at room temperature. The single phase has been observed due to tantalum substitution which leads total conductivity of σ = 1.35 x 10^-4 Scm^-1.

Abstract: Despite growing interest in geopolymers-graphene oxide (GO) composites for energy-responsive construction materials, quantitative correlations between thermoelectric performance, thermal properties, density, and mechanical behavior remain limited, and the optimal GO loading that balances multifunctional performance has not been clearly established. In this study, fly ash–based geopolymer composites incorporating GO (0-2 g) were systematically investigated to elucidate thermoelectric, microstructural, and mechanical responses. The results show that moderate GO incorporation establishes conductive networks that improve both charge and heat transfer while enhancing matrix densification and interfacial bonding. Significant increases in the Seebeck coefficient and thermoelectric voltage were observed, suggesting improved charge-carrier transport and thermoelectric conversion efficiency. SEM-EDS images showed a denser, more homogeneous matrix with reduced porosity, while mechanical tests revealed greater toughness and ductility due to crack-bridging and nanosheet pull-out mechanisms. In contrast, excessive GO addition caused agglomeration and reduced matrix cohesion. The GO incorporation significantly enhances thermal conductivity and Seebeck coefficient, indicating improved heat and charge transport through conductive GO networks. Consequently, the thermoelectric figure of merit (ZT) increased nearly fourfold. Conversely, the specific heat capacity (C_p) slightly decreased, reflecting reduced lattice heat storage due to matrix densification. The optimal GO content (approximately 1 g) achieved the best balance between mechanical integrity and thermal–electrical performance. These findings establish clear structure-property-performance relationships and demonstrate the potential of GO-modified geopolymers as multifunctional and energy-responsive materials for advanced construction and thermoelectric applications.