Effect Of Lattice Distortion Research Articles

Temperature-induced lattice distortion in CuGeO3 nanocrystals

Lattice distortion represents the fundamental factor of crystalline materials and contributes significantly to structural-related properties. Herein, we discover an unexpected temperature-induced lattice distortion in CuGeO3 nanocrystals, resulting in color changes of CuGeO3. The structural distortions in CuGeO3 nanocrystals are characterized by Rietveld analysis in detail, where its cell parameter b and cell volume reveal first decrease and then increase characteristics and correspond well with the XRD patterns and Raman spectra. Besides, both the experimental characterizations and theoretical calculations confirm that the optical and band structural changes mainly arise from the twisted octahedral field of [CuO6], where the lattice distortions regulate the crystal field splitting energy of [CuO6] and account for its changed d-d transition. Furthermore, tetracycline photodegradation is employed as an example to evaluate the effect of lattice distortion on photocatalytic performance, which also highlights the importance of modulating lattice distortion in photocatalysis. This work provides an approach to simply regulate the lattice distortion for nanorods by manipulating calcination temperatures.

Quantitative analysis of atomic-scale local lattice distortions in high-entropy fluorite oxide (Zr0·2Ce0.2Hf0.2Y0·2Al0.2)O2-δ

Novel high-entropy oxides have attracted considerable attention as promising candidates for high-temperature structural applications. The lattice distortion effect in such materials is closely related to their microstructural evolution and thermophysical performance. In this study, the local lattice distortions in the high-entropy fluorite oxide (Zr0·2Ce0.2Hf0.2Y0·2Al0.2)O2-δ were observed at the atomic scale using aberration-corrected scanning transmission electron microscopy and studied quantitatively using geometric phase analysis. The results showed that the radius and brightness of the atomic column projections exhibit slight variations owing to the random distribution of the cations, resulting in differences in the relative contents of the five elements in each atomic column. The anions were influenced by both the random distribution of the cations and the large number of oxygen vacancies, leading to M-O-M (M = Zr, Ce, Hf, Y, and Al) bond angles of 80–105°. The distributions of strains εyy and εxx (along the lattice spacing direction and vertical direction, respectively) within the crystal structure were mainly centred around ±4%, and there was a tendency for alternating positive and negative values in strains maps without significant aggregations. In addition, strains εxx and εyy increased significantly to 26.4% and 9.2%, respectively, within the dislocation areas.

A practical method to enhance the properties of Pr/Nd-lean sintered RE-Fe-B magnets: High entropy design for RE2Fe14B

In this study, single main phase (SMP) magnets with high-entropy RE2Fe14B were prepared, which contained La, Ce, Pr, Nd and Y. The microstructure and properties of the magnets were studied. The results show that the magnets with high entropy design have a higher melting temperature (Tm) of RE2Fe14B (1189.5℃), less REFe2 and finer grains (mean grain size: 4.51 μm) compared with binary main phase (BMP) magnets of (LaCe)-Fe-B mixed with (PrNd)-Fe-B. This is mainly due to the high entropy effect, lattice distortion effect and sluggish diffusion from the high-entropy RE2Fe14B, as well as the synergism of the rare earth (RE) elements. The properties of the magnets are enhanced, especially the magnetic properties. Maximum energy product (BH)max of 33.48 MGOe is achieved with only 40 wt% Pr/Nd in total RE. This work provides a valuable method to obtain RE-Fe-B magnets with high cost performance.

Effects of lattice distortion and chemical short-range ordering on the incipient behavior of Ti-based multi-principal element alloys: MD simulations and DFT calculations

One of key factors in designing high-performance alloys is to understand their incipient behavior. To get detailed real-time atomic scale evolutions of multi-principal element alloys (MPEAs) during nanoindentation incipient yielding, molecular dynamics (MD) simulations were carried out. Emphases are given to the effects of lattice distortion (LD) and chemical short-range ordering (CSRO) on the initiation of plasticity in body-centered cubic (BCC) MPEAs. The initial plastic mechanism is embryo nucleation assisted and the incipient behavior is strongly affected by LD and CSRO. Specifically, the embryo nucleation load Pe is reduced by LD and CSRO and the incipient drop P0 is lowered by LDI that only comes from atomic size difference and further declined by CSRO. This is because LD and CSRO could boost embryo nucleation, which can act as precursors for dislocation nucleation. This is consistent with the free-end nudged elastic band observations. Although Pe is weakened by LDII generated by introducing extra elements, P0 is intensified because severe LD could dominate the following process. The dislocation starvation mechanism is found in an average-atom (AA) model. However, it is replaced by dislocation interactions due to LD and CSRO. Density functional theory (DFT) calculations suggest that charge density distribution and the amount of directional Al-Al bonding would play a critical role in the onset of plastic deformation. When a larger indenter radius was used in MD simulations, the dislocation starvation mechanism is absent in AA model due to the reduced maximum shear stress. Instead, the dislocation propagation prevails. With respect to the orientation effect, three investigated orientations demonstrate a distinct yielding behavior.

Unique dislocation loops distribution of AlCrFeNiTix eutectic high-entropy alloys under high-temperature ion irradiation

Eutectic high-entropy alloys (EHEAs) have drawn great attention due to their excellent high-temperature mechanical properties. A group of EHEAs AlCrFeNiTix with different titanium contents was irradiated with 3 MeV Fe11+ ions at 500 °C with fluences of 9.1 × 1014 and 4.55 × 1015 ions/cm2. The disordered body-centered-cubic (BCC, A2) exhibited smaller-sized dislocation loops than those of ordered BCC (B2) based on Transmission electron microscopy (TEM) analysis. The type of loops found in AlCrFeNi alloy were<100>and 1/2<111>. The fraction of 1/2<111>was higher, indicating the excellent irradiation resistance of EHEAs. Small size and large density of dislocation loops formed after the addition of Ti. Phase boundaries in the alloys could effectively decrease the density and size of dislocation loops because of defects annihilation at phase boundaries. In combination with density function theory (DFT) results. B2 phase exhibited better energy landscape advantage in the Ti accommodating, and the MSD results indicated that the lattice distortion effect caused by Ti entering B2 phase was more obvious than A2 according to the density function theory (DFT) results. Our research exhibited a beneficial scheme for solid solution strengthening of elements in EHEAs, and provided an insight into the suppression of dislocation loops under irradiation.

Investigating the Impact of Displacement Cascades on Tritium Diffusion in MgT2: A Molecular Dynamics Study.

Molecular dynamics methods were utilized to investigate displacement cascades and tritium diffusion in α-MgT2. It was observed from collision cascades results that the stable number of defects weakly depended on temperature, while the peak and stable number of defects linearly increased with increasing the primary knock-on atom energy. The results of the mean square displacement study revealed that defects had a significant impact on tritium diffusion. The clustering of magnesium self-interstitial atoms and diffusing tritium atoms results in an increased diffusion barrier, whereas the formation of clusters between tritium interstitial atoms is relatively difficult and has no significant impact on the diffusion barrier. The presence of magnesium and tritium vacancies has a minimal effect on the diffusion barrier due to the large number of diffusing tritium atoms that offset the adsorption of vacancies on diffusing atoms. Both magnesium and tritium interstitial atoms increase the collision probability of diffusing atoms, leading to an increased diffusion prefactor. Magnesium vacancies cause significant lattice distortion, increasing the diffusion barrier, while the impact of tritium vacancies on the diffusion barrier is small due to their minimal lattice distortion effect. The research uncovered significant disparities in the diffusion properties of hydrogen and tritium, indicating that the results of the study of hydrogen storage could not be applied to tritium.

Effect of Sb-induced oxygen octahedral distortion on piezoelectric performance and thermal stability of Pb(In,Nb)O3-Pb(Hf,Ti)O3 ceramics

The combination of excellent thermal stability and outstanding electrical performance is of great significance for piezoelectric ceramics. Herein, we have prepared 0.11Pb(In0.5Nb0.5)O3-0.89Pb(Hf0.47Ti0.53)O3-Sb2O5 (PIN-PHT-xSb) ceramics by solid-phase method and investigated the effect of oxygen octahedral lattice distortion on microstructure and macroscopic electrical properties. The distortion index of oxygen octahedra is studied by Rietveld refinement, showing that optimal octahedral distortion can soften B-O repulsion, disrupt long-range ordered ferroelectric domains, and enhance local heterogeneities, significantly increasing piezoelectric properties. Moreover, outstanding thermal stability and ultrahigh piezoelectric response of PIN-PHT-1.2Sb ceramics are realized under the synergistic influence of octahedral distortion, excellent density, and large grain size. Compared with PIN-PHT ceramics, PIN-PHT-1.2Sb ceramics exhibit ultrahigh piezoelectric responses (d33 = 706 pC/N, kp = 0.68, εr = 3244), a high Curie temperature (TC) of 300 °C, excellent thermal stability, and anti-fatigue properties.

A neural network model for high entropy alloy design

A neural network model is developed to search vast compositional space of high entropy alloys (HEAs). The model predicts the mechanical properties of HEAs better than several other models. It’s because the special structure of the model helps the model understand the characteristics of constituent elements of HEAs. In addition, thermodynamics descriptors were utilized as input to the model so that the model predicts better by understanding the thermodynamic properties of HEAs. A conditional random search, which is good at finding local optimal values, was selected as the inverse predictor and designed two HEAs using the model. We experimentally verified that the HEAs have the best combination of strength and ductility and this proves the validity of the model and alloy design method. The strengthening mechanism of the designed HEAs is further discussed based on microstructure and lattice distortion effect. The present alloy design approach, specialized in finding multiple local optima, could help researchers design an infinite number of new alloys with interesting properties.

High entropy effect on double exchange interaction and charge ordering in half doped Nd0.5Sr0.5MnO3 manganite

The entropy stabilized oxides i.e., the so-called high-entropy oxides are of great interest in recent time due to their intriguing physical properties. This new category of advanced materials is stabilized by the high configurational entropy of randomly mixed elements, where a specific lattice site is populated by five or more elements. The present study is devoted to explore the high entropy effect in well-known charge ordered manganite Nd0.5Sr0.5MnO3 where a delicate balance exists between the ferromagnetic double exchange and the antiferromagnetic superexchange interactions. Powder X-ray diffraction analyses confirm phase purity of the samples. FE-SEM imaging revealed the microstructure and elemental mapping confirmed the chemical homogeneity of the samples as well as nominal cationic composition. Bond valence sum (BVS) calculation using refinement parameters supports the expected cationic valence in all the samples. Replacement of Nd3+ by five trivalent cations as in (La0.1Pr0.1Nd0.1Gd0.1Bi0.1)Sr0.5MnO3 with larger average A-site ionic radius,<rA>and smaller size variance, σ2 compared with Nd0.5Sr0.5MnO3 dramatically suppressed the ferromagnetic double exchange interaction. This observation is in contrast with the expected variation in<rA>and σ2. In (La0.1Nd0.1Gd0.1Bi0.1Y0.1)Sr0.5MnO3 with smaller<rA> and marginally higher σ2 the ferromagnetic state ceases to exist. In both the multicationic compositions, a long-range antiferromagnetic state is evolved around 200 K with the retention of charge ordering. In the high entropy (La1/6Nd1/6Dy1/6Ca1/6Ba1/6Sr1/6)MnO3 composition with nominal<rA> and larger σ2 values the high temperature long-range ordering is completely suppressed and a new antiferromagnetic state is evolved at 45 K without manifestation of any charge ordering. This composition also avoids magnetic frustration unlike the dopant variant with larger σ2. The present investigation thus highlights the role of local lattice distortion or high entropy effect apart from the<rA>and σ2 in manganites.

OVERVIEW OF THE HIGH-ENTROPY ALLOYS CONCEPT

The article presents a review of the results of research on high-entropy alloys, describing the principles of their formation, the basic concepts and properties of high-entropy alloys. The existing categories of the entropic alloys are listed. The effects resulting from the formation of high-entropy alloys are described: high entropy, lattice distortion, sluggish diffusion and cocktail effects. It is noted that the traditional thermodynamic representations for multicomponent alloys require additions. It is also noted that the application of Hume-Rothery rules to predict the phase composition of high-entropy alloys shows some difficulties, since it is difficult to select a large number of elements having the same type of lattice and valence. The results of the analysis of a number of parameters and conditions which, according to the researchers' opinion, affect the structural state created by high-entropy alloys, taking into account which could allow to correctly predict the formation of structures in high-entropy. Analysis of the literature data has shown that at present there is no universal parameter that could allow the correct prediction of the formation of structures in multicomponent alloys systems. Methods for the preparation of powders of high entropy alloys are presented. The results of frequently used methods of obtaining coatings on the basis of high-entropy alloys, such as laser cladding, magnetron sputtering, electrochemical deposition and thermal spraying are reviewed. Disadvantages of obtaining coatings methods are described.

Effect of alloying elements on elastic properties, generalized stacking fault energy, and critical resolved shear stress of Pd metal: A first principle study

Functional alloying elements (B, Si, P, Ti, V, Zn, Ga, In and Sn) and impurity elements (H and O) have an impact on the mechanical performance complexly. In order to clarify the effect of those elements, the elastic properties, generalized stacking fault energies and critical resolved shear stress of the Pd-X alloys were comprehensively analyzed by first-principle method. The variation of those elastic and ductile properties via alloying elements has been obtained. Crystal chemical analysis shows that the ionic bond between Pd and O determines the stability of O occupying tetrahedral site. Meanwhile, the energy barrier and dislocation distribution analysis support that the perfect dislocation will be decomposed to partial dislocations during the critical slip. According to electronic structure analysis, the increase of ductility (i.e., the decrease of unstable stacking fault energy along 112¯ directions) is attributed to the decrease of charge density on the slip surface. Moreover, a criterion, called misfit ratio R = |εs/εb|, is introduced to clarify major contribution of solid solution strengthening ΔτCRSS/c2/3 is lattice distortion effect or GSFE change effect caused by alloying elements.

Probing the atomic-scale deformation mechanism of single-crystal nanowires coated with a multi-component alloyed shell

Metallic nanowires have attained considerable attention as applied for the building blocks in nano-electromechanical systems. Surface coating is needed for nanowires to prevent their degradation from the external environment. Multi-component alloys (MCAs) exhibit a combination of exceptional fracture tolerance and desirable corrosion resistance, which are promising coating materials for nanowires. However, few attempts have been made to investigate the deformation mechanisms of nanowires coated with an MCA shell. To address this gap, we employ atomic simulations on investigating the tensile deformation of single-crystal nickel nanowires coated with MCA shells, and study the microstructural features governing the necking behavior of these specimens. The results indicate that the dislocation nucleation method controlling the incipient plasticity of the nanowire turns from a typical homogeneous surface nucleation mode to another interface nucleation one after coating, lowering the maximum stress during the tensile loading. Ductile necking with dispersed plastic events prevails in the uncoated nanowire, while severely localized shear dominates the necking mode of the single- and poly-crystalline MCA nanowire due to their lower dislocation contents as well as the sluggish dislocation mobility caused by lattice distortion and high-entropy effect. The necking mode of nanowires is not altered by the MCA coating due to the predominant volume fraction of the nickel core in the present configurations. Noteworthily, the deformation stability is highly enhanced by polycrystalline MCA coating, thus the stress no longer drops to zero before the final fracture. This work gives new insights into developing reliable nanowires with enhanced deformability via using MCA coating.

Electroplasticity in the Al0.6CoCrFeNiMn high entropy alloy subjected to electrically-assisted uniaxial tension

Electrically assisted deformation (EAD) was adopted in this work to overcome the shortcomings such as poor formability and easy cracking in the processing of dual-phase the Al0.6CoCrFeNiMn high entropy alloy (HEA) at room temperature. Electroplasticity of the Al0.6CoCrFeNiMn HEA was studied systematically using electrically assisted uniaxial tension. The results showed that pulse current caused the temperature gradient along the tensile direction and the temperatures of the samples increased with the current density. The flow stress decreased, and the elongation increased with increasing current density during the EAD. When the current density was 30 A mm–2, the total elongation of the samples could be increased by 50% compared to that with no pulse. Pulse current can reduce local stress concentration and postpone microcracks initiation in the body-centered cubic (BCC) phases, and hence can effectively inhibit cracks and ruptures. The dislocation tangles were opened by pulse current, and the dislocation recovery was enhanced at a high current density. Compared with dilute solid solution alloys, the lattice distortion effect, the high fraction of the BCC phases, and the dislocations in HEAs can lead to the enhancement of the local Joule heating, which accelerated dislocation slip and dislocation annihilation. This study confirms that EAD can effectively improve the formability of HEAs and provides theoretical guidance and an experimental basis for forming HEAs components.

Research Progress of High Entropy Materials as Water Electrolysis Catalysts in Recent Years

Hydrogen energy has drawn considerable attention in recent years, among which the efficient production of hydrogen energy from water electrolysis has become a hot research topic in this field. The oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in water electrolysis are the core of the catalytic efficiency. High entropy materials have excellent combinatorial properties due to their "cocktail effect", high entropy effect, slow diffusion effect, and lattice distortion effect. They have outstanding catalytic effect in the process of water electrolysis, and thus become a hot research topic in recent years. This review combines the two hot topics by introducing the up-to-date research progress of high entropy materials in catalyzing water electrolysis. First, evaluation indexes of electrocatalytic performance are explained. Second, this review demonstrates specific materials from the classification of high entropy alloys, high entropy oxides and nitrided high entropy materials, which includes the structure of the materials and their specific catalytic performance. Finally, it summarizes the research progress of high entropy materials in water electrolysis catalysis as well as gives an outlook on the future design direction of the materials.

Lattice distortion and re-distortion affecting irradiation tolerance in high entropy alloys.

High entropy alloys (HEAs) are promising nuclear structural materials due to their excellent irradiation resistance. However, the essential mechanisms of irradiation tolerance in HEAs remain largely inferential and imperfectly understood. This study investigates the evolution of irradiation-induced nano-scale microstructures in Ni, FeNiCr, FeNiCrCoCu and FeNiCrCuAl HEA models by molecular dynamics simulations to elucidate the conundrums. As fewer irradiation-induced Frenkel pair (FP) residuals were found in the FeNiCrCuAl HEA model in comparison with other models, a high resistance of the HEAs to the generation of permanent defects was indicated, while also the associated relatively long thermal spike and slow recrystallization stimulated a high efficiency for the recombination/annihilation of FPs to underscore a superior structural recovery of the HEAs. Under the influence of compositional increases of constituent elements, the effect of severe lattice distortion by energetics modifications was found to stimulate decreased atomic mobility accompanied by inhibited dislocation formation. The evolution of the models' lattices in terms of their capacity to restrict interstitials and repair defects revealed that the self-healing/recovery mechanism that confirmed the highest initial lattice distortion value accompanied by the least lattice re-distortion value in the FeNiCrCuAl HEA model is key to the observed superior irradiation tolerance of the HEA models. Thus, by feasibly enhancing lattice distortion in crystalline materials, notably in HEAs, promising and potentially high irradiation-resistant structural materials can be developed.

Microstructure and properties of Cu-Al-Ni-Mn-Y alloy with precipitation and effective strengthening by aging treatment

The Cu-11Al-3Ni-2.5Mn-1Y alloy prepared by hot-press sintering was subjected to aging treatment at different temperatures of 350 °C, 400 °C, 450 °C, 500 °C and 550 °C, respectively. The phase composition, microstructure, mechanical and damping properties were characterized. The results show that the alloys after the ageing treatment are mainly composed of 18 R martensite and 2 H martensite. The precipitation phase begins to appear and the best comprehensive properties are obtained at the aging temperature of 450 °C. The hardness and strength values reached 347.6 HV and 642.6 MPa, respectively. The strengthening mechanisms are mainly involved in lattice distortion and dislocation increment effect caused by solution strengthening, shearing and hindering effect of precipitated phases and dislocations, fine grain strengthening effect caused by grain size reduction, and the increase of large angle grain boundary. Simultaneously, the room temperature damping reached 0.0723, which is 93 % higher than the original sample of 0.38. The improvement of damping properties is closely related to the changes in the number and size of martensite, the interfacial damping effect caused by precipitated phases, and the pinning and unpinning reaction between dislocations and precipitated phases. Therefore, alloys with both high mechanical and high damping properties can be obtained by proper aging treatment. In addition, the increase in phase transition temperature of high temperature damping properties also provides some guidance for the exploration and development of this alloy in the high temperature field.

Effects of lattice distortion and chemical short-range order on creep behavior of medium-entropy alloy CoCrNi

Creep behavior of multi-principal element alloys (MPEAs) is an intriguing topic to explore for their potential high-temperature applications. The challenge on this topic is to elucidate what effect the local chemical fluctuation has on the creep behavior of MPEAs. By using large-scale molecular dynamics (MD) simulations, we investigate the creep performances of CoCrNi medium-entropy alloys (MEAs) with and without chemical short-range order (CSRO) as well as the Average-atom (A-atom) counterpart (no lattice distortion (LD)) under different uniaxial tensile stresses at various elevated temperatures. A power-law model is adopted to analyze the implicit stress exponent and activation energy, which are associated with the creep mechanism and creep resistance, respectively. The results reveal CSRO rather than LD plays an important role in creep performance. Specifically, with the introduction of CSRO, the activation energy for creep in CoCrNi MEA is significantly increased and finally close to the activation energy for the diffusion of the Cr element that is the highest among the three elements (Co, Cr, and Ni). The CoCr clusters in the MEA with CSRO make it difficult to increase the shear strain in the creep process, resulting in a much lower creep rate than that of the CoCrNi MEA without CSRO. For the CoCrNi MEA without CSRO, grain boundary diffusion is the main creep mechanism. For the MEAs with CSRO, the predominant creep mechanism depends on the applied stress. At low stress, grain boundary diffusion still prevails and there is no obvious dislocation glide or grain boundary sliding. When the applied stress is high enough, grain boundary diffusion and dislocation slip dominate the creep behavior, accompanied by the occurrence of grain boundary sliding.

A Lightweight AlTiVNb High-Entropy Alloy Film with High Strength-Ductility Synergy and Corrosion Resistance.

The simultaneous improvement of mechanical and corrosion resistance is of great significance for engineering applications. In this work, a novel lightweight amorphous structure AlTiVNb high-entropy alloy (HEA) film was fabricated by magnetron sputtering. The compression test of the AlTiVNb HEA film nanopillar exhibits a high compressive strength of up to 3.6 GPa and deformability approaching 58%. The high strength is affected by the disordered state, the nanostructure, and the lattice distortion effect, while the high ductility comes from the ductile shear band and the island structure. In addition, the AlTiVNb HEA film shows a current density of 4.90 × 10-8 A/cm2 and a potential of -0.234 V in the 3.5% NaCl solution, comparable to that of the 316L stainless steel. The chemical disorder state, cocktail effect, and homogeneous amorphous structure contribute to excellent corrosion resistance. This finding offers new insights into high-performance HEA films with robust mechanical and anticorrosion performances for microelectronic devices and mechanical metamaterials.

Atomistic simulations of dislocation plasticity in concentrated VCoNi medium entropy alloys: Effects of lattice distortion and short range order

Face-centered cubic (fcc) high and medium entropy alloys (H/MEAs) have been shown to display superior mechanical properties at low temperatures, but significant improvement of their strength at high temperatures is required for industrial applications at extreme conditions. Recently, it has been shown that the breakthrough of the MEAs from equiatomic/near-equiatomic to non-equiatomic ratios leads to strong MEAs with good ductility. To design new H/MEAs, we consider two important factors that may influence strength: the chemical composition and chemical short range order (CSRO). In this study, we investigate the depinning stress (σc) as a criterion of strength of several compositions of VCoNi concentrated solid solution alloys (CSSAs) including V0.33Co0.33Ni0.33, V0.35Co0.2Ni0.45, V0.33Co0.17Ni0.5, and V0.17Co0.33Ni0.5 at 5 K and 300 K, using atomistic simulations. The chosen interatomic potential is shown to be reliable by comparing experimental/ab initio values and calculated parameters such as lattice constant, shear modulus, depinning stress, and temperature variation of stacking fault width for equimolar VCoNi. We find a good agreement between experimental friction stress and the depinning stress extracted from our results for equimolar VCoNi. Also, we find that Vclusters are the main pinning points of dislocations, and With a random distribution of atoms, we find that the alloy composition V0.33Co0.17Ni0.5 displays the largest depinning stress at both 5 and 300 K. Furthermore, to investigate how CSRO affects the strength of these alloys, we design CSRO into the microstructure using two different methods: In the first method, hybrid Molecular-dynamics/Monte-Carlo simulations were employed to simulate annealing at various temperatures. We observe that such simulations create CSRO so that it increases with decreasing annealing temperature. Recently, the CSRO motif and its concentration in an equimolar VCoNi have been determined by experiment. By modeling this experiment, we also implemented the CSRO into microstructure as the second method. By using both methods, the effect of CSRO on the magnitude of the depinning stress is discussed. It was shown that in both methods, CSRO significantly influences the strength of non-equimolar VCoNi alloys.

Microstructure-dependent thermal conductivity and mechanical properties in cast Mg-4Sm-xAl alloys

The thermal conductivity of Mg-Sm binary alloys is relatively poor due to the severe lattice distortion introduced by the high solid solubility Sm atom in the Mg matrix, which restricts their widespread application. In this study, the viability of Al alloying (0–2.6 wt%) in permanent mold cast Mg-4Sm (wt.%) alloy was investigated to design cast Mg alloys with high thermal conductivity. It is found that the thermal conductivity significantly improved with the addition of Al content, and peaked at 136.8 W/(m·K) with an Al content of 1.5 wt%, which is attributed to the release of the Sm atoms from the Mg matrix. It is also confirmed that minimizing the lattice distortion effect is critical to achieving high thermal conductivity. The formation of Al2Sm and Al11Sm3 phases leads to a dramatic decline in solid solution strengthening due to its strong consumption of the dissolved Sm atoms, but in the meantime enhances secondary phase strengthening and promotes stronger interactions between different strengthening components. The optimum combination of mechanical properties and thermal conductivity is obtained in Mg-4Sm-2Al alloy, which possesses a yield strength of 102.6 MPa, elongation of 6.8% and thermal conductivity of 124.5 W/(m·K), compared with several commercial as-cast Mg alloys.