Explore the vast range of titles available.

A combination of quantum mechanics calculations with machine learning techniques can lead to a paradigm shift in our ability to predict materials properties from first principles. Here we show that on-the-fly training of an interatomic potential described through moment tensors provides the same accuracy as state-of-the-art ab initio molecular dynamics in predicting high-temperature elastic properties of materials with two orders of magnitude less computational effort. Using the technique, we investigate high-temperature bcc phase of titanium and predict very weak, Elinvar, temperature dependence of its elastic moduli, similar to the behavior of the so-called GUM Ti-based alloys (Sato et al 2003 Science 300 464). Given the fact that GUM alloys have complex chemical compositions and operate at room temperature, Elinvar properties of elemental bcc-Ti observed in the wide temperature interval 1100-1700 K is unique.

The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various industrial applications, from actuators and medical devices to high-precision instruments 1 , 2 . The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys 3 —including gum metals 4 , 5 and strain glass alloys 6 , 7 —may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation 3 . Recently, chemically complex alloys, such as ‘high-entropy’ alloys 8 , have attracted tremendous research interest owing to their promising properties 9 – 15 . In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10 −4 ) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported. A chemically complex alloy that exhibits a high elastic strain limit and low internal friction is described; it also has an Elinvar effect (invariant elastic modulus) over a large temperature range, up to 627 °C.

This study investigates the effect of heat treatment on the microstructure and Elinvar properties of a cold-rolled 40NiCrTiAl alloy. This study utilizes optical microscopy, scanning electron microscopy backscattered electron imaging, secondary electron imaging, and energy-dispersive X-ray spectroscopy analysis to observe the precipitation behavior and determine the composition within the material. The results show that the 40NiCrTiAl Elinvar alloy at aging temperatures of 600-700°C, spherical precipitates appear within the grains. At approximately 700°C and with an aging time of around 2 hours, the precipitate volume reaches a peak, and the Young’s modulus and Elastic modulus temperature coefficient also reach their respective peaks. These elastic performance indicators exhibit a strong linear relationship with the degree of precipitate formation. These findings are important for a deeper understanding of the application potential and performance optimization of this Elinvar alloy.

Fast development of space technologies poses a strong challenge for elastic materials, which need to be not only lightweight, strong and compliant, but also able to maintain stable elasticity over a wide temperature range 1 – 4 . Here we report a lightweight magnesium–scandium strain glass alloy (Mg with 21.3 at.% Sc) that meets this challenge. This alloy is as light (density ~2 g cm –3 ) and compliant as organic-based materials 5 – 7 like bones and glass fibre reinforced plastics, but in contrast with those materials, it possesses a nearly temperature-independent (or Elinvar-type), ultralow Young’s modulus (~20–23 GPa) over a wide temperature range from room temperature down to 123 K; a higher yield strength of ~200–270 MPa; and a long fatigue life of over one million cycles. As a result, it exhibits a relatively high, temperature-independent elastic energy density of ~0.5 kJ kg –1 among known materials at a moderate stress level of 200 MPa. We show that its exceptional properties stem from a strain glass transition, and the Elinvar-type elasticity originates from its moderate elastic softening effect cancelling out the ever-present elastic hardening. Our findings provide insight into designing materials that possess unconventional and technologically important elastic properties. Temperature-independent (Elinvar) soft elasticity with high strength, which is technologically desired but scientifically challenging, is achieved in a lightweight strain glass Mg alloy.

High-performance superelastic materials with a combination of high superelastic stress, large elastic recovery strain, and stable elastic modulus over a wide temperature range are highly desired for a variety of technological applications. Unfortunately, it is difficult to achieve these multi-functionalities simultaneously because most superelastic materials have to encounter the modulus softening effect and the limited superelastic stress, whereas most Elinvar-type materials show small elastic strain limit. Here, we report a (TiZrHf) 44 Ni 25 Cu 15 Co 10 Nb 6 high-entropy alloy that meets all these requirements. This alloy also shows good cyclic stability, thermally-stable capacity for elastic energy storage, high micro-hardness and good corrosion resistance, allowing it to operate stably in hostile environments. We show that its multi-functionalities stem from a natural composite microstructure, containing a highly-distorted matrix phase with strain glass transition and various structural and compositional heterogeneities from micro- to nano-scale. Our findings may provide insight into designing high-entropy alloys with unconventional and technologically-important functional properties. Designing superelastic materials with high critical stress, large recovery strain and temperature-independent modulus is desired but challenging. Here, the authors achieve these properties in a high-entropy alloy with multi-scale heterogeneities.

This paper examines the phonon dispersion and static local atomic distortion of iron-manganese-based Elinvar alloys using high-resolution inelastic X-ray scattering, magnetization, neutron diffraction, and neutron total scattering. In this study, nonlinear phonon dispersion was observed for a transverse acoustic mode near zone center, associated with elastic constants, over a wide temperature range along the to X (310) points of the face-centered cubic system, indicating lattice instability coupled with tetragonal distortions in the long-wavelength limit. Bulk magnetization and neutron diffraction measurements suggest that the conventional ferromagnetic magnetostriction scenario is not the origin of Elinvar characteristics. Instead, the martensitic transformation and lattice instabilities underlie these phenomena. The reduced pair distribution function reveals a significant discrepancy between local and global (averaged) structures suggesting the influence of atomic-scale lattice disorder and instability in FeMn-based Elinvar alloys.

This study investigates the effect of aging temperature on the physical properties of Fe–40.32Ni–5.51Cr–2.63Ti–0.47Al–0.55Mn–0.40Si–0.016C (wt.%) alloy using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, a physical-property measurement system, and a dilatometer, among others. After a solution treatment, the microstructure of the experimental alloy was composed of the γ phase. The aging process involved the precipitation of the γ ’ and η phases to regulate the Elinvar effect. No martensite or ferrite phases were observed in either the solid-solution or aged samples using X-ray diffraction and transmission electron microscopy. The Elinvar effect for traditional Fe–Ni–Cr ferromagnetic Elinvar alloys is related to spontaneous magnetisation, resulting in spontaneous volume magnetostriction. The inflection temperature of the elastic modulus exceeded the Curie temperature. The larger the precipitation amount, the weaker the ΔE effect, and the larger the Young’s modulus value. For a holding time of 2 h, the amount of precipitation was maximised at an aging temperature of 650 °C, while Young’s modulus and its temperature coefficient achieved maxima of 190 GPa and 9.0 × 10⁻ 5  °C⁻ 1 , respectively. In addition, the lattice constant at room temperature indirectly reflects the amount of precipitation. Young’s modulus, the temperature coefficient of Young’s modulus, the Curie temperature, and the linear-expansion coefficient obeyed an approximately parabolic law as functions of the lattice constant or its reciprocal. Moreover, Young’s modulus and its temperature coefficient can be estimated using the Curie temperature and linear-expansion coefficient, respectively.

This study presents the experimental results of structural analysis of the phase composition, grain size, plasticity, and hardness of the elinvar Ni-span-C alloy 902 after various heat treatment modes (quenching and quenching with subsequent aging). A thermal treatment mode has been selected to obtain higher physical and mechanical properties of the elinvar alloy. It is shown that the improvement of the alloy structure under thermal treatment occurs due to the thermal stresses, as well as the formation and dissolution of intermetallides.

Strain glass, a short-range strain-ordered state of martensitic/ferroelastic material, has drawn much interest in recent years due to its novel properties unattainable in martensitic materials. So far, typical or conventional strain glasses have been reported to be characterized by nano-sized martensitic domains formed from a homogeneous parent phase matrix. This article reviews the recent progress in “non-conventional strain glass,” which is different from the conventional strain glasses reported so far. We first introduce a “reentrant strain glass,” where strain glass nanodomains are formed from a martensitic phase instead of from a parent phase. The reentrant strain glass can show low modulus and high damping properties over a wide temperature range. The second non-conventional strain glass is a “spinodal strain glass” produced by a spinodal decomposition in its early stage. This unique strain glass is formed from a nanoscale compositionally inhomogeneous parent phase (by spinodal decomposition). The spinodal strain glass demonstrates high-damping Elinvar effect over an ultrawide temperature range. These non-conventional strain glass alloys may have potential for novel applications as new structural–functional materials.

Super strength and toughness, excellent deformation resistance, and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings (TBCs). The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength–plasticity and the reduction of service performance. Introducing preexisting twin boundaries and stacking faults (SFs) or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics. However, due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature, the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs. In this paper, the deformation behavior of high configuration entropy Zr 6 Ta 2 O 17 ceramics at 25 to 1,200 °C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment. A remarkable Elinvar-like effect appears in the Zr 6 Ta 2 O 17 ceramic. More interestingly, mechanical deformation dominates the severe lattice distortion (deformation twins, SFs) and the disorder–order transition of chemical order at the atomic scale, while temperature can further enhance the degree of lattice distortion and ordering of Zr 6 Ta 2 O 17 ceramics. Furthermore, the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr 6 Ta 2 O 17 ceramics.