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This study compares the tensile properties of single-phase and dual-phase polycrystalline FeNiAl alloys using molecular dynamics (MD) simulation. The findings reveal that dual-phase polycrystalline materials, incorporating both B2-NiAl and face-centered cubic (FCC)-Fe phases, exhibit significantly superior strength and strain hardening compared to their single-phase FCC-FeNiAl counterparts. The back stress and Bauschinger effect emerge as pivotal factors in strengthening and strain hardening during the tensile deformation of dual-phase polycrystalline materials. In single-phase polycrystalline materials, grain plastic deformation is uniform, primarily driven by Shockley partial dislocation b = 1 6 < 121 > . Additionally, deformation twinning is observed with increasing strain. Conversely, in dual-phase polycrystalline materials, non-uniform plastic deformation occurs because of differences in crystal structure between the two phases. Plastic deformation predominantly takes place in the soft domain FCC-Fe grains, while dislocations encounter hindrance from the hard domain B2-NiAl grains, leading to the generation of back stress. The direction of dislocation movement opposes the back stress, further impeding plastic deformation and enhancing material strength. In cases where the back stress is sufficiently high, the dislocation source may halt dislocation emission, creating significant stress concentration between soft and hard domains, consequently causing local stress and strain and ultimately leading to crack formation. The comprehension of these mechanisms provides a valuable reference for developing FeNiAl alloys with exceptional mechanical properties. [ABSTRACT FROM AUTHOR]

The influence of microstructures (bimodal and basketweave) on the tensile properties and deformation mechanism of Ti-5Al-1V-1Sn-1Zr-0.8Mo alloy was investigated via an in situ tensile test monitored by electron backscatter diffraction (EBSD)-assisted slip trace analysis. The bimodal structure exhibited good plasticity, but its tensile strength was lower than that of the basketweave structure. These variations could be attributed to the larger α colony structure in the basketweave structure. In situ tensile testing showed that the α colony in the basketweave structure can promote the formation of shear bands, leading to decreased plasticity. The activation of numerous slip systems in αp of the bimodal structure ensured good plasticity. Meanwhile, deformation twins were occasionally observed in the bimodal structure. However, dislocation slip and deformation twins were observed inside the large-sized grain boundary α (αGB) phase in the basketweave structure. The results of this study can extend the potential application of Ti alloys. [ABSTRACT FROM AUTHOR]

Ceramic aerogels are highly efficient, lightweight, and chemically stable thermal insulation materials but their application is hindered by their brittleness and low strength. Flexible nanostructure-assembled compressible aerogels have been developed to overcome the brittleness but they still show low strength, leading to insufficient load-bearing capacity. Here we designed and fabricated a laminated SiC-SiOx nanowire aerogel that exhibits reversible compressibility, recoverable buckling deformation, ductile tensile deformation, and simultaneous high strength of up to an order of magnitude larger than other ceramic aerogels. The aerogel also shows good thermal stability ranging from −196 °C in liquid nitrogen to above 1200 °C in butane blow torch, and good thermal insulation performance with a thermal conductivity of 39.3 ± 0.4 mW m−1 K−1. These integrated properties make the aerogel a promising candidate for mechanically robust and highly efficient flexible thermal insulation materials. Mechanically robust, flexible and thermally insulating ceramic aerogels are challenging to obtain due to the conflicting nature of these properties. Here the authors resolved these contradictions and developed a strong yet flexible aerogel, for application in extreme conditions, by laminated structure design. [ABSTRACT FROM AUTHOR]

Ni–Co alloy has high temperature resistance, corrosion resistance, excellent magnetic and catalytic capabilities, and is widely used in energy development, chemical industry, electronics, aviation and aerospace, such as combustion chamber hot end parts, aircraft engine working blades and hydrogen evolution catalysts. It is well known that the properties of materials depend on the structure and morphology, which depend on the preparation method. At present, the main methods for preparing nano-Ni–Co alloy are electrodeposition, sol–gel method and solution reduction method. The parameters in these preparation methods affect the morphology and properties of nano-Ni–Co alloy, so it is particularly important to study the influence of various parameters on the properties of Ni–Co alloy. In this work, the preparation methods and research progress of nano-Ni–Co alloy in recent decades are summarized, hoping to provide valuable information for the development of Ni–Co alloy. [ABSTRACT FROM AUTHOR]

A kind of micro/nanostructured 2205 duplex stainless steel (DSS) with uniform distribution of nanocrystals was prepared via aluminothermic reaction method. The analysis of stress-strain curve showed that the fracture strength and elongation of the specimen were 946 MPa and 24.7%, respectively. At present, the research on microstructure of bimodal 2205 DSS at room temperature (RT) mainly depended on scanning electron microscope (SEM) observation after loading experiments. The test result indicates that there are two different yield stages in stress-strain curve of specimen during tensile process. The microstructure of duplex bimodal structured stainless steel consists of two pairs of soft hard regions and phases. By studying deformation mechanism of bimodal structured stainless steel, the interaction between soft phase and hard phase are discussed. The principle of composition design and microstructure control of typical duplex stainless steel is obtained, which provides an important research basis for designing of advanced duplex stainless steel. [ABSTRACT FROM AUTHOR]

In this contribution, molecular dynamics method is used to accurately add quantitative Co atoms in the grain boundary (GB) region of nano-polycrystalline Ni to study the effect of solute atoms on the GB and the deformation mechanism of the material. It was found that adding an appropriate amount of Co atoms at the GBs can improve the tensile strength of the material to a certain extent through solid solution strengthening. However, excessive introduction of solute atom will increase the activity of GB atoms, destroy the stability of GBs, and accelerate the appearance of material yielding. At the same time, the Co atoms at the GB gradually detached from the GB region and diffused into the grains. In addition, the dislocations are distributed in a grid at the GBs, and with the increase in strain, the number and length of dislocations gradually increase, forming a large number of entanglements. Moreover, the Shockley dislocation interacts with other dislocations to form a more stable dislocation structure by hindering the generation and movement of other dislocations, which greatly enhances the strength of the system. [ABSTRACT FROM AUTHOR]

The ω-phase in metastable β-titanium (Ti) alloys attracts great research interests owing to the metastability and the involved microstructural complexity upon straining, while the fundamental understanding on its formation mechanism is still insufficient. In this study, deformation-induced ω-plates have been systematically investigated using Ti-10 wt% Cr metastable β-Ti alloy containing athermal ω-precipitates. It is found that single-variant ω-plates form either along {332}β twin interfaces or in the twin interiors, which closely depends on twin morphologies. For the acicular β-twin, the ω-plate appears in the twin interiors accompanied by high density of parallel straight dislocations, while for the lenticular twin, the ω-plate attaches to the twin interface without the surrounding dense parallel straight dislocations. These unique formation characteristics result from local stress field induced by the twinning itself and the passive transformation of athermal ω-precipitates. It is further revealed that the passive transformation of athermal ω-precipitates dominates the formation of ω-plates inside the acicular twins, while it is the locally preferential twin thickening that promotes the ω-plates to form along the lenticular twin interfaces. These findings provide new insight into deformation-induced ω-phase transformation and the intricate deformation microstructures in metastable β-Ti alloys. [ABSTRACT FROM AUTHOR]

Electrochemical carbon monoxide reduction is a promising strategy for the production of value-added multicarbon compounds, albeit yielding diverse products with low selectivities and Faradaic efficiencies. Here, copper single atoms anchored to Ti3C2Tx MXene nanosheets are firstly demonstrated as effective and robust catalysts for electrochemical carbon monoxide reduction, achieving an ultrahigh selectivity of 98% for the formation of multicarbon products. Particularly, it exhibits a high Faradaic efficiency of 71% towards ethylene at −0.7 V versus the reversible hydrogen electrode, superior to the previously reported copper-based catalysts. Besides, it shows a stable activity during the 68-h electrolysis. Theoretical simulations reveal that atomically dispersed Cu–O3 sites favor the C–C coupling of carbon monoxide molecules to generate the key *CO-CHO species, and then induce the decreased free energy barrier of the potential-determining step, thus accounting for the high activity and selectivity of copper single atoms for carbon monoxide reduction. Electrochemical carbon monoxide reduction is a promising strategy to yield valuable multicarbon products but low selectivities and Faradaic efficiencies are common. Here the authors show single atom copper catalyst supported on MXene with high CO reduction performance and stability. [ABSTRACT FROM AUTHOR]

In this work, we use the finite element method to investigate the free volume evolution, as well as the martensite transformation effect and its connection with the pretreatment strain, in a shape memory alloy-metallic glass composite. Our simulation results show that the martensite phase transformation can enhance the blocking effect while relieving the free volume localization. The synergistic effect among the martensite transformation effect, blocking effect, and shear band interaction in the composite is responsible for the tensile plasticity and work-hardening capability. In addition, we design a Sierpinski carpet-like fractal microstructure so that the composite exhibits improved tensile performance as a result of the enhanced synergistic effect. However, the tensile performance of the composite deteriorates with increasing pretreatment strain since the martensite transformation effect is weakened. [ABSTRACT FROM AUTHOR]

A continuous martensite transformation is indispensable for achieving large linear superelasticity and low modulus in phase transforming metal-based composites. However, determining how to accurately condition the residual martensite in a shape memory alloy matrix though the reinforcement shape to achieve continuous martensite transformation has been a challenge. Here, we take the finite element method to perform a comparative study of the effects of nanoinclusion shape on the interaction and martensite phase transformation in this new composite. Two typical samples are compared: one reinforced by metallic nanowires and the other by nanoparticles. We find that the residual martensite within the shape memory alloy matrix after a pretreatment can be tailored by the reinforcement shape. In particular, our results show that the shape memory alloy matrix can retain enough residual martensite phases to achieve continuous martensite transformation in the subsequent loading when the aspect ratio of nanoreinforcement is larger than 20. In contrast, the composites reinforced with spherical or low aspect ratio reinforcement show a typical nonlinear superelasticity as a result of a low stress transfer-induced discontinuous martensite transformation within the shape memory alloy matrix. [ABSTRACT FROM AUTHOR]