High Strength Levels Research Articles

Preliminary Investigation on the Application of a Semi-Lightweight Mullite Spherical Solid Waste Material in Ladle Permanent Layer

The heat dissipation of high alumina castables for ladle permanent layer is a topic worthy of attention and solution. It is proposed to use spherical porous mullite (a solid waste) instead of irregular M70 mullite aggregate in castable to reduce the thermal conductivity and realize a high-strength and lightweight design. The effect of spherical porous mullite content in castables on thermal conductivity, service strength and thermal shock resistance were discussed. The results demonstrated that the substitution amount of spherical porous mullite increased, the bulk densities of the castables dropped from 2.68 to 2.38 g.cm−3, the apparent porosity rose from 15.5 to 25.0%. The thermal conductivities reduced from 1.174 to 0.585 W.m−1.K−1 (1000°C), which can be ascribed to the increased porosity extending the heat transfer path. Furthermore, owing to the high strength of spherical mullite and its excellent bonding with matrix, the mechanical strength of castable was at a high strength level, with modulus of rupture of 18 M Pa and cold crushing strength of 76 MPa at the spherical porous mullite completely substituting M 70 mullite. The semi-lightweight and low thermal conductivity castable containing spherical porous mullite show great application potential in the ladle permanent layer.

SELECTION OF TECHNOLOGICAL PARAMETERS OF MODES FOR MANUAL ARC WELDING OF SHUT-OFF VALVES MADE OF STEEL ALLOYED WITH 3–4 % NICKEL

Body of ball valves can be manufactured from A350-LF3 steel according to the US standard ASTM A350, alloyed with nickel up to 4 %. This steel has a tendency to harden in the heat affected zone during welding. The results of computer simulation showed that cooling rates during shielded metal arc welding exceed the recommended range. This can lead to the formation of hardening structures, the development of cold cracks and a decrease in the performance properties of welded joints of ball valves made of A350-LF3 steel.
 To prevent the formation of cold cracks, the preheating and concurrent heating temperatures were calculated. According to the results of computer simulation, it was found that pre-heating and concurrent heating provide the cooling rate of heat affected zone in the recommended range.
 The technology has been developed for welding ball valves made of A350-LF3 steel with mounting nozzles. This technology prevents the formation of cold cracks and provides a high level of strength and toughness of welded joints. The high level of mechanical properties of welded joints is confirmed by results of mechanical tests and metallographic studies.

High cycle fatigue properties of high-nitrogen steel hot-rolled with the yield strength level of 1000 MPa

The fatigue properties of an Fe-19Cr-20Mn-0.6N high-nitrogen steel (HNS), which was hot-rolled with the yield strength level of 1000 MPa, were investigated by means of tension–tension fatigue tests. The results showed that the fatigue life increased in a power law manner with the decrease of the maximum stress from 1040 MPa to 880 MPa. The fatigue limit at the 107 cycles was about 840 MPa, with the ratios of the fatigue limit to yield strength and tensile strength being 0.79 and 0.69, respectively. The high fatigue limit could be attributed to its high yield strength level, which was resulted from the mixed microstructure consisting of ultrafine grains and elongated grains with some slip bands.

Effect of Deformation-Induced Plasticity in Low-Alloyed Al-Mg-Zr Alloy Processed by High-Pressure Torsion

The influence of additional deformation heat treatments (DHTs), implemented by two regimes: (1) annealing and small additional deformation by high-pressure torsion (HPT) at room temperature (RT) and (2) HPT at elevated temperature to 10 turns and small additional HPT at RT, has been studied on the microstructure, mechanical properties and electrical conductivity of ultrafine-grained (UFG) Al-0.53Mg-0.27Zr (wt.%) alloy structured by HPT to 10 turns at RT. As is shown, both types of additional DHT lead to a substantial increase in plasticity (2–5 times) while maintaining high electrical conductivity (~53% IACS) and strength comprising 75–85% of the value in the pre-DHT state of the UFG alloy. The possible physical reasons for the revealed changes in the physical and mechanical properties are analyzed. Comparison of the strength and plasticity changes with the microstructure evolution after DHT of both types indicates that the increase in the density of introduced grain boundary dislocations is the most probable factor providing a tremendous increase in plasticity while maintaining a high level of strength in the UFG alloy under study. An outstanding combination of high strength (370 MPa), high elongation to failure (~15%) and significant electrical conductivity (~53% IACS) was achieved for the Al-Mg-Zr alloy. This combination of properties exceeds those obtained to date for this system, as well as for a number of other commercial conductor alloys based on the Al-Zr system.

The influence of L12 ordered precipitates on hydrogen embrittlement behavior in CoCrNi-based medium entropy alloys

The recently emerged multicomponent (or medium/high entropy) alloys have generated considerable excitement globally in the last 10 years because of their excellent mechanical and functional properties, particularly in terms of strength-ductility combinations that can surpass most other metallic materials. However, the achieved high strength level (above 1 GPa in many cases) fuels strong concerns about hydrogen embrittlement (HE). Detailed investigation in this field is still scarce, especially pertaining to the face-centered cubic medium entropy alloys (MEA) that are typically strengthened by ordered precipitates. Here, we unravel the effect of γ' (L12) ordered precipitates on H-induced damage behavior and the associated HE resistance in CoCrNi-based MEAs. Compared with the equi-molar CoCrNi MEA, the precipitation-hardened (CoCrNi)94Al3Ti3 MEA shows an enhanced HE resistance even at a higher strength level. Both alloys are fractured due to H-assisted intergranular cracking at the initial failure stage when loaded in the presence of H. The formation of intergranular cracks is primarily attributed to the H-induced decohesion at grain boundaries, where a high stress/strain concentration accompanied by a more intensive dislocation planar slip (or stacking fault formation) caused by H was observed. The presence of γ' precipitates serves to slow down the internal diffusion/migration of H due to the trapping effects. The precipitates with a relatively larger size (∼50 nm) also hinder dislocation planar slip thus decreasing the number of pile-up dislocations at grain boundaries. Both effects collectively reduce the tendency of H-induced intergranular cracking, leading to the improved HE resistance. The work reveals the positive role of ordered precipitates in H tolerance and thus provides some insights in further microstructure design of medium/high entropy alloys for applications in H-abundant environment.

Comparing the associations between muscle strength, walking speed, and mortality in community-dwelling older adults of two birth cohorts born 28 years apart

Reduced age-specific mortality and increased muscle strength and walking speed of current older adults may have altered the relationships between these factors as more people may be above the reserve capacity threshold. We compared the cross-sectional associations between muscle strength and walking speed, and the associations of muscle strength and walking speed with five-year mortality between two population-based cohorts of 75- and 80-year-old people born 28 years apart. Maximal isometric grip and knee extension strength and walking speed were measured in 2017–2018 (n = 726). Mortality was ascertained from registers. The associations were compared with data of same-aged people studied in 1989–1990 with identical protocols (n = 500). The knee extension strength-walking speed relationship showed plateauing at higher strength levels among the later-born men, whereas the earlier-born men and women of both cohorts with lower strength levels were on the linear part of the curve. In the later-born women with lower five-year mortality rate (1.16 vs. 5.88 per 100 person-years), the association between grip strength and mortality was markedly different from the earlier cohort (HR 1.13 [95% CI 0.47–2.70] vs. 0.57 [0.37–0.86]). For knee extension strength and walking speed, the mortality hazards were similar between the cohorts, although statistically non-significant in the later-born women. In men, the later-born cohort showed similar associations as observed in the earlier-born cohort despite having lower mortality rate (2.93 vs. 6.44). Current older adults have more functional reserve that will likely help them to maintain walking ability for longer while also contributing to better survival.

Model development and validation for human serum proteins- membrane interactions: Membrane fouling applications in ultrafiltration of patients blood

The DLVO theory, named after the founders Derjaguin, Landau, Verwey, Overbeek, and its derivatives have been successfully used to predict membrane fouling by macromolecules such as proteins. Despite the theory’s success, the calculations involved require extensive measurements. Furthermore, deviations are observed at certain experimental conditions such as at high ionic strengths. Our study aims to develop a linear regression model to address those limitations and reduce the number of required measurements required and associated multistep calculations related to DLVO. Our developed regression model correlates the pseudo-steady normalized flux to the charges, hydrophobicity, and size/ pore size of the foulant(s) (e.g., human serum protein) and the membrane. To verify the validity of the regression model, we extracted data from various peer-reviewed journal articles. The predicted flux using our developed model agreed with the experimental data within 90% confidence intervals. Furthermore, our developed regression model seems to be less sensitive to high ionic strength levels compared to the DLVO and xDLVO, resulting in better correlations. Overall, the results suggest that the fouling phenomena can be predicted using a simple regression equation with readily measurable parameters, such as human serum protein and membrane properties. To conclude, our model only requires particle and membrane’s zeta potentials, their size/pore size, and their water contact angles (compared to water contact angles, glycerol contact angles, and diiodomethane contact angles required for xDLVO) to predict fouling behavior.

Low-Temperature Superplasticity of the 1565ch Al–Mg Alloy in Ultrafine-Grained and Nanostructured States

—Homogeneous nanostructured and ultrafine grained (NS, UFG) states with mean grain sizes of 95 and 200 nm, respectively, have been formed in a 1565ch Al–Mg alloy (Al–5.66Mg–0.81Mn–0.67Zn–0.09Zr–0.07Cr–0.04Ti–0.001Be–0.3(Fe + Si) wt %). Microstructure of both states is represented by grain boundaries with predominantly high-angle misorientations. The alloy, produced both by high pressure torsion at room temperature and equal channel angular pressing at 200°C using the Conform approach, exhibits superplasticity at low temperatures in the range 250–300°C and strain rates in the range of 5 × 10–4–10–2 s–1. Elongation values range 170–560%, while the rate sensitivity coefficient (m) varies from 0.3 to 0.73 at low flow stress for both NS and UFG structures. The temperature range for the stability of strength properties of the 1565ch alloy in NS and UFG states after thermal and thermal mechanical treatments has been determined. The material in both structural states maintains a high level of strength after undergoing deformation under SP conditions. The deformation relief formed on the gage surface of the NS and UFG specimens of the 1565ch alloy during the established SP yield stage has been analyzed.

MANIFESTATION OF SUPERPLASTICITY AT LOWER TEMPERATURES OF 1565CH ALLOY OF THE Al−Mg SYSTEM IN ULTRAFINE-GRAIN AND NANOSTRUCTURAL STATES

In this work, homogeneous nanostructured and ultrafine-grained (NS and UFG) states with an average grain size of 95 nm and 200 nm, respectively, are formed in the 1565ch alloy of the Al-Mg system. In both states, the microstructure is formed by a network of predominantly high-angle grain boundaries. It has been shown that an alloy with an NS and UFG structure formed at room temperature by high-pressure torsion (HPT) and at 200°C by equal-channel angular pressing according to the Conform scheme (ECAP-С) exhibits similar signs of superplastic (SP) behavior at low temperatures 250 …300 °С in the range of strain rates 5×10-4 s-1…10-2 s-1: elongation values were 170…560%, the rate sensitivity coefficient (m) was 0.3-0.73 at low flow stresses . The temperature range of stability of the strength characteristics of the 1565ch alloy in the NS and UFG states was established, both after thermal and deformation-thermal treatment. It is shown that the material in both studied structural states retains a high level of strength after deformation under SP conditions. The deformation relief formed on the working part of the NS and UFG samples of the 1565ch alloy at the stage of a steady-state SP flow is analyzed.

Quasi-static tests of squat reinforced concrete shear walls with openings

Due to the high level of stiffness and strength, Squat Reinforced Concrete Shear Walls (SRCSWs) with or without openings are frequently utilized in various types of buildings. However, the adverse effect of openings on the seismic performance of the SRCSWs has never been investigated in detail. Therefore, for truly disclosing the seismic behaviors of the SRCSWs with openings, six 1/2.7 scale SRCSW specimens are experimentally investigated through Quasi-Static Testing (QST) in this paper. The affecting factors in terms of the Shear Span Ratio (SSR), the area ratio, and the number of openings are considered. Based on the experimental results, the seismic performance in terms of failure modes, hysteretic loops, skeleton curves, ductility factors, stiffness degradations, energy dissipations, and deformation components was analyzed and discussed. It is shown that shear failure was observed on the SRCSWs without openings, while the SRCSWs with openings are prone to flexural failure, e.g., the flexural deformation ratios ranging from 49.66% to 58.99%. It is shown from the experimental results that the area ratio and the SSR significantly affect the seismic response of SRCSWs, generally speaking, with the increase of the area ratio and/or SSR the bearing capacity and the secant stiffness are reduced. It is also shown that for the case of multi-openings, the cracks are focused on the connecting areas between two openings. The results indicate that the seismic design of SRCSWs should consider the effect of openings in order to enhance the seismic performance.

Linear Layer Architecture Based on Cyclic Shift and XOR

One of the nodes of a block symmetric encryption algorithm is represented by a linear layer, the purpose of which is to distribute the mutual influence of bits within the processed data block. Several methods exist for constructing a linear layer, the most common of which are matrix multiplication operations and the permutation of bits. Both approaches have high computational complexity and are not equally effective for both hardware and software implementations. This paper presents an approach for constructing linear functions for block symmetric encryption algorithms utilizing cyclic shift, and bitwise addition operations are formulated. We provide a preliminary assessment of certain properties of such functions, including the branch number. This linear operation can accommodate binary words of any length, allowing for the design of an optimal linear layer for software or hardware architectures with any word size. Furthermore, the developed architecture allows for balancing the laboriousness of linear operations and related branch numbers. The proposed novel linear layer architecture facilitates the creation of fast lightweight encryption algorithms as well as robust classical algorithms with a high level of cryptographic strength. For efficient implementation on software and hardware platforms, no additional optimizations are required, as the proposed linear layer allows for achieving high performance in both cases.

Interpretation of SLC3A1 and SLC7A9 variants in cystinuria patients: The significance of the PM3 criterion and protein stability

Cystinuria is a genetic disorder caused by defects in the b0,+ transporter system, which is composed of rBAT and b0,+AT coded by SLC3A1 and SLC7A9, respectively. Variants in SLC3A1 and SLC7A9 follow autosomal recessive inheritance and autosomal dominant inheritance with reduced penetrance, respectively, which complicates the interpretation of cystinuria-related variants. Here, we report seven different SLC3A1 variants and six different SLC7A9 variants. Among these variants were two novel variants previously not reported: SLC3A1 c.223C > T and SLC7A9 c.404A > G. In silico analysis using REVEL correlated well with the functional loss upon SLC7A9 variants with scores of 0.8560–0.9200 and 0.4970–0.5239 for severe and mild decrease in transport activity, respectively. In addition, DynaMut2 was able to predict a decreased protein expression level resulting from the SLC7A9 variant c.313G > A with a ΔΔGStability −2.93 kcal/mol. Our study adds to the literature as additional cases of a variant allow applying the PM3 criterion with higher strength level. In addition, we suggest the clinical utility of REVEL and DynaMut2 in interpreting SLC3A1 and SLC7A9 variants. While a decreased protein expression level is not embraced in the current variant interpretation guidelines, we believe in silico protein stability predicting tools could serve as evidence of protein function loss.

Upper Extremity Injury Related to Wheeled Recreational Device-Hoverboard: A Case Report

ABSTRACT Hoverboards were designed for making our Daily life easier. However, lots of patients admitted to emergency services due to. These devices require a high level of balance, coordination and strength. Traumatic injuries are more common especially in children and young adults. Forearm fractures are one of the important trauma outcomes in the pediatric age group. Although supracondylar or forearm fractures are common, we rarely encounter a combination of both, defined as floating arm fractures. A 9-year-old boy falling from a hoverboard had supracondylar humerus fractures accompanied by olecranon and distal Radius fractures in the same arm. A temporary long arm splint was applied to the patient who was transferred to the orthopedic clinic and surgical operation was planned for stabilization. In our case, we aimed to discuss the coexistence of olecranon and distal radius fracture accompanying ipsilateral supracondylar humerus fracture in a child hoverboard user.

Deep-learning image reconstruction for 80-kVp pancreatic CT protocol: Comparison of image quality and pancreatic ductal adenocarcinoma visibility with hybrid-iterative reconstruction

PurposeTo evaluate the image quality and visibility of pancreatic ductal adenocarcinoma (PDAC) in 80-kVp pancreatic CT protocol and compare them between hybrid-iterative reconstruction (IR) and deep-learning image reconstruction (DLIR) algorithms. MethodA total of 56 patients who underwent 80-kVp pancreatic protocol CT for pancreatic disease evaluation from January 2022 to July 2022 were included in this retrospective study. Among them, 20 PDACs were observed. The CT raw data were reconstructed using 40% adaptive statistical IR-Veo (hybrid-IR group) and DLIR at medium- and high-strength levels (DLIR-M and DLIR-H groups, respectively). The CT attenuation of the abdominal aorta, pancreas, and PDAC (if present) at the pancreatic phase and those of the portal vein and liver at the portal venous phase; background noise; signal-to-noise ratio (SNR) of these anatomical structures; and tumor-to-pancreas contrast-to-noise ratio (CNR) were calculated. The confidence scores for the image noise, overall image quality, and visibility of PDAC were qualitatively assigned using a five-point scale. Quantitative and qualitative parameters were compared among the three groups using Friedman test. ResultsThe CT attenuation of all anatomical structures were comparable among the three groups (P = .26–.86), except that of the pancreas (P = .001). Background noise was lower (P <.001) and SNRs (P <.001) and tumor-to-pancreas CNR (P <.001) were higher in the DLIR-H group than those in the other two groups. The image noise, overall image quality, and visibility of PDAC were better in the DLIR-H group than in the other two groups (P <.001–.003). ConclusionIn 80-kVp pancreatic CT protocol, DLIR at a high-strength level improved image quality and visibility of PDAC.

Unveiling the unique bifunctionality of L12-structured nanoprecipitates in a FeCoNiAlTi-type high-entropy alloy

Nanoprecipitation strengthening has been widely adopted as an effective way to design high-strength alloys, which generally leads to the loss of ductility. Here we unveil the unique bifunctionality of L12-structured nanoprecipitates in a FeCoNiAlTi-type high entropy alloy (HEA), enabling the combined increase of tensile strength and ductility. Results show that as-quenched precipitate-free matrix alloys undergo thermally-induced martensite transformation and form the body-centered cubic (BCC) martensite phase with limited tensile ductility. In strong contrast, when introducing the dense coherent L12-type nanoprecipitates, the face-centered cubic (FCC) matrix is temporarily stabilized, which in turn promotes the microbands-induced plasticity associated with stress-induced martensite transformation upon deformation. This allows us to achieve significantly improved work hardening capability and excellent plastic deformation stability at a high-strength level. These new findings reshape our understanding of the precipitation strengthening and could provide useful guidance for developing high-performance alloys by regulating the coherent nanoprecipitate and martensitic phase transformation.

A State-of-the-Art Review of Organic Polymer Modifiers for Slope Eco-Engineering.

In slope ecological restoration projects, reinforcing soil and promoting vegetation growth are essential measures. Guest soil spraying technology can be used to backfill modified soil and vegetation seeds onto the slope surface, resulting in successful ecological restoration. The use of organic polymer modifiers to reinforce soil has several benefits, such as high strength, effective results, and low pollution levels. Organic polymer soil modifiers can be divided into two categories: synthetic polymer modifiers and biopolymer modifiers. This paper provides a thorough review of the properties and interaction mechanisms of two types of polymer modifiers in soil consolidation. The properties of organic polymer modifiers make them applicable in soil and vegetation engineering on slopes. These modifiers can enhance soil mechanics, infiltration, and erosion resistance and promote vegetation growth. Therefore, the suitability of organic polymer modifiers for soil and vegetation engineering on slopes is demonstrated by their properties and potential for improvement in key areas. Furthermore, challenges and future prospects for slope protection technology using organic polymer modifiers are suggested.

Mechanical Properties Evaluation of Laminated Composites of Petung Bamboo (Dendrocalamus asper) and Coconut Coir Fiber as Ship Construction Components

The high demand for steel and wood as the primary shipbuilding materials will increase market prices due to decreasing supplies each year. To address this issue, new alternative materials that are more environmentally friendly and inexpensive, such as natural fibers like bamboo and coconut fiber, must be explored. This study aimed to investigate how the directional arrangement (0° unidirectional and 90° unidirectional) of laminated Petung bamboo (Dendrocalamus asper) affects the compressive and flexural strength of ship construction. The compressive strength on the X, Y, and Z-axis was measured to determine the laminated beam’s strength ratio on each side. In contrast, the flexural strength was only observed on the Y and Z-axis due to testing equipment limitations. The results showed that the directional arrangement of laminated Petung bamboo with different test axes significantly impacted the compressive and flexural strength of laminated beams made of Petung bamboo and coconut coir fiber. Laminated Petung bamboo and coconut coir fiber with 0° unidirectional fiber had better compressive and flexural strength values than those with 90° unidirectional fiber. Based on the data testing, the combination of Petung bamboo and coconut coir fiber materials can be categorized into different strength classes. These findings have important implications for using laminated bamboo in shipbuilding applications. The use of laminated bamboo with a 0° lamina direction could be recommended for ship components that require high levels of strength than laminated bamboo with a 90° lamina direction.

A facile, semi-automatic protocol for the design and production of 3D printed, anatomical customized orthopedic casts for forearm fractures

Closed fractures of distal radius and ulna are one of the most common skeletal injuries, occurring at all ages. Temporary arm immobilization through cast is part of the standard treatments. However, traditional casting procedures are time consuming, operator's skill dependent and do not always guarantee a satisfactory outcome. From a clinical perspective, casts are often considered uncomfortable and can be associated to skin lesions. To overcome these limitations, the recent growth of 3D technologies has enabled new standardized casting procedures: additive manufacturing (AM) is a technique that creates highly customized cast models from anatomical 3D data by using digitally controlled and operated material laying tools. Compared with conventional casts, those produced with AM technique could potentially reduce skin complications and satisfy both mechanical and clinical requirements of functionality, comfort, and aesthetics.The objective of this study is to describe the new practical methodology to produce a 3D printable cast for upper arm immobilization. The parametric modelling tool, employed to develop a semi-automatic design system for generating the printable cast model, reduces the complex process of orthosis design to a few minutes and all the manufacturing operations remain unaffected by CAD skills of the operator. Specific hardware and software tools (3D scanner, modelling software and FDM technology) were chosen to mitigate design and production costs while guaranteeing suitable levels of data accuracy, process efficiency and design versatility. To highlight the effectiveness of the proposed solution, a finite element analysis simulation was performed on models with different geometry, highlighting the mechanical strength of generated structures.The final result is a personalized 3D printed cast with a highly ventilated structure that is lightweight but still maintains a high level of strength and provides hygienic benefits, reducing the risk of cutaneous complications, potentially improving treatment efficacy and increasing patient satisfaction.

STUDY OF THE INFLUENCE OF SILVER ALLOYING ON THE MICROSTRUCTURE AND PROPERTIES OF MAGNESIUM ALLOY NZ30K FOR IMPLANTS IN OSTEOSYNTHESIS

Purpose. Study of the influence of silver alloying of magnesium alloy NZ30K on its mechanical properties for use in the manufacture of biodegradable implants. Research methods. The tensile strength and relative elongation of the samples were determined on a P5 tensile machine at room temperature. The microstructure of the samples was studied using a “Carl Zeiss” optical electron microscope using the “Observer.D1m” software. Samples were used after etching with a reagent containing 1 % nitric acid, 20 % acetic acid, 19 % distilled water, and 60 % ethylene glycol. Fractographic analysis of sample fractures was performed on a JSM-6360LA scanning electron microscope. The phase analysis of the structural components of magnesium alloys was studied using an electron microscope – a microanalyzer with an energy dispersive attachment РEMMA 202М and РЕМ 16I. Research on biocorrosion was carried out by keeping the samples in a solution of gelofusin – an artificial blood substitute for 2, 4, 6 weeks, using a TC-20 MICROmed thermostat. Results. The study showed that silver was a part of the complex alloyed intermetallic phases, which were additional crystallization centers. In this case, the average grain size decreases by almost three times compared to the original alloy. It was found that the optimal set of properties is achieved by the introduction of 0.1 % Ag, while the tensile strength increases by 7.9 % and the relative elongation almost doubles. It was found that the magnesium alloy with silver (0.1 %) slows down biocorrosion processes and helps to maintain a high level of tensile strength (σB = 205 MPa) after 6 weeks of exposure to a solution of helofusine. Thus, silver is a promising material for improving the structure and increasing the mechanical properties of biodegradable magnesium alloy implants. Scientific novelty. The silver content for alloying the NZ30K alloy was determined to be 0.1 % Ag, which forms the optimal ratio of strength and ductility, grain structure refinement, and slowing down biocorrosion processes. Practical value. NZ30K alloy with the addition of 0.1 % silver is promising for use in the manufacture of implants. The studied alloy provides the required level of properties until complete fracture consolidation.

Achieving ultrahigh strength and ductility in high-entropy alloys via dual precipitation

The strength-ductility trade-off has been a longstanding dilemma in metallic materials. Here we report an innovative approach to achieve a high strength-ductility synergy via dual precipitation of sheared and bypassed precipitates. (Ni2Co2FeCr)96–xAl4Nbx (at.%) alloys strengthened by nanoscale L12 particles and Laves precipitates were selected as a model for this study, and their precipitate microstructures and mechanical properties were thoroughly investigated. The dual-precipitation-strengthened alloys exhibit a yield strength of more than 1400 MPa, an ultimate tensile strength of over 1800 MPa, and a uniform elongation of 18%, thus achieving a high strength-ductility synergy. Our analysis reveals that the nanoscale L12 precipitates contribute to the strength via the particle shearing mechanism, whereas the Laves phase provides the strengthening through the Orowan bypass mechanism. The study of deformation microstructures shows that the L12 precipitates are sheared by stacking faults, which facilitates long-range dislocation gliding through the matrix. As a result, deformation induces the formation of hierarchical stacking fault networks and immobile Lomer–Cottrell locks, which effectively enhance the work hardening capability and plastic stability, thereby resulting in a high ductility at high strength levels. Dislocations are piled-up against the interface between the Laves precipitates and matrix, which increases the work hardening capability at the early stages of plastic deformation but causes stress concentrations. The dual precipitation strategy may be useful for many other alloys for achieving superior mechanical properties for technological applications.