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The trade‐off relation between strength and plasticity is the bottleneck that limits the development of high‐strength and high‐plasticity Al–Cu alloys. Inspired from the influence of precipitate shape on the work‐hardening behavior of Al–Cu alloys, an Al–Cu–Zr–Sc alloy containing a mixed microstructure of spherical‐shaped Al3(Zr, Sc) phases and disk‐shaped θ′ phases is successfully designed and fabricated. Surprisingly, it is found that the strength and plasticity of the Al–Cu–Zr–Sc alloy are synchronously improved compared to the Al–Cu alloy with only disk‐shaped θ′ phases. The introduction of spherical‐shaped Al3(Zr, Sc) phases can increase the yield strength without sacrificing the work‐hardening ability of the Al–Cu–Zr–Sc alloy, which is mainly attributed to the extremely small strain‐hardening exponent of the Al alloy with spherical‐shaped precipitates. Besides, the predicted strength–elongation relation of the Al–Cu alloy is established based on the exponential strain‐hardening model. [ABSTRACT FROM AUTHOR]

During the selective laser melting (SLM) process of Ti6Al4V, a special structure can be formed with columnar prior β grains along the building direction and fully martensitic α′ within the β grain. To investigate the influence of such special structure on the fatigue crack growth (FCG) rate, Ti6Al4V specimens fabricated by SLM were heat‐treated at two different temperatures in this study. The columnar grains were retained, and the martensite was decomposed when heat‐treated below the β transus. It is found that all the SLM features were removed when heat‐treated above the β transus. FCG rate tests were subsequently performed at room temperature, and it was found that the prior β grains affected the macroscopic fracture morphology, but there was no discernible influence on the FCG rate. The morphology of the α phase affected the crack growth path and the FCG rate. Changes in the strength‐toughness relationship induced by heat treatment can help understand the decrease in the FCG rate. Highlights: Heat treatments at two temperatures were used to eliminate SLM features.The morphology of the α phase affected the fatigue crack growth path and rate.The strength‐toughness relationship can help to understand the variation of FCG rate. [ABSTRACT FROM AUTHOR]

In the process of electric power transmission, the defects in the copper wire interact with the electrons which results in a thermal effect, accordingly, causing the changes of microstructure and properties of the copper wire. Herein, the evolution of microstructure, strength, and electrical conductivity of the oxygen‐free copper wires annealed at different temperatures is investigated. In addition, the effects of various microstructures on strength and electrical conductivity are quantitatively revealed. In the low‐temperature region (80–150 °C), dislocation recovery is the main reason for the decrease in strength; while, the increase in electrical conductivity is mainly due to the decrease in dislocation density and the transformation of grain boundary from nonequilibrium state to equilibrium state. In the high‐temperature region (above 210 °C), the strength loss is mainly related to the increasing recrystallized grain size and the disappearance of dislocations in the recrystallized region. The increase in electrical conductivity is mainly attributed to the significant decrease in grain boundary density and the further recovery of dislocations. [ABSTRACT FROM AUTHOR]

Taking lessons from nature offers an increasing promise toward improved performance in man‐made materials. Here new cement materials with unidirectionally porous architectures are developed by replicating the designs of natural wood using a simplified ice‐templating technique in light of the retention of ice‐templated architectures by utilizing the self‐hardening nature of cement. The wood‐like cement exhibits higher strengths at equal densities than other porous cement‐based materials along with unique multifunctional properties, including effective thermal insulation at the transverse profile, controllable water permeability along the vertical direction, and the easy adjustment to be water repulsive by hydrophobic treatment. The strengths are quantitatively interpreted by discerning the effects of differing types of pores using an equivalent element approach. The simultaneous achievement of high strength and multifunctionality makes the wood‐like cement promising for applications as new building materials, and verifies the effectiveness of wood‐mimetic designs in creating new high‐performance materials. The simple fabrication procedure by omitting the freeze‐drying treatment can also promote a better efficiency of ice‐templating technique for the mass production in engineering and may be extended to other material systems. [ABSTRACT FROM AUTHOR]

Based on the principle of skin effect, a pure Al clad Al alloy wire is designed to break the mutually exclusive relation between strength and electrical conductivity. Actually, bimetallic composite wires offer the ability to blend the desired properties of various metals into a single wire, for example, combining the high‐conductivity of pure Al (outer layer) and the high‐strength of Al alloy (core). Thus, a novel method is adopted to prepare a pure Al clad Al alloy wire (ACAW) and the metallurgical bonding between pure Al and Al alloy is achieved by compressing the Al alloy cylinder into a hollow pure Al cylinder followed by a series of processes including forging, rolling, and cold‐drawing. A perfect interface is obtained as the fine grains are found across the interface. Furthermore, a linear rule of mixtures is applied to calculate the performance of ACAW as compared with the measured performance of ACAW. The measured strength of ACAW is the same as the calculated strength. Interestingly, the measured electrical conductivity of ACAW (58.17%IACS) is higher than the calculated electrical conductivity (57.60%IACS). Consequently, ACAW is an effective approach for combining the high‐conductivity of pure Al and the high‐strength of Al alloy. [ABSTRACT FROM AUTHOR]

The Al–Si piston alloys always bear different temperatures because of its peculiar component structure and service condition. Therefore, the tensile strength, elongation to fracture, and corresponding damage mechanisms of Al12SiCuNiMg piston alloys (ASPA) have been investigated with in situ technique at different temperatures. The tensile properties show two‐stage tendencies: the former stage (25–280 °C) is determined by easily broken phases with inherent brittleness (such as primary Si), and the fracture behavior presents rapid brittle fracture after reaching the critical stress (about 430 MPa, based on in situ technique and the elastic stress field model). The later one (280–425 °C) is dominated by particles debonding and θphase coarsening. The plastic deformation behavior, dynamic recovery, and flow process become more significant on account of thermal activation. The Considère criterion h = K indicates that the transition of damage behaviors from insufficient local strength to insufficient matrix strength and the corresponding failure model shifts from brittle to ductile fracture. Based on the damage mechanisms, the elastic field model and thermal activation relation model have been established to characterize the strength of the ASPA at different temperature ranges. [ABSTRACT FROM AUTHOR]

[Display omitted] While materials that are light, strong, tough and simultaneously damping are highly attractive for a range of applications, it remains a challenge to achieve a combination of all these properties in a single material as these properties are often mutually exclusive. Here we present a cermet material comprising an ultrafine-grained Mg-Al-Zn magnesium alloy with ultrafine Ti 3 AlC 2 ceramic platelets, where the two phases are bi-continuous and interpenetrated in 3D space yet are alternately arranged in a layered fashion as in natural nacre. Such an architecture was constructed by infiltrating the alloy into the porous ceramic scaffold where the Ti 3 AlC 2 platelets were preferentially aligned by vacuum filtration and partially sintered. The resulting cermet exhibits a high flexural strength exceeding 1 GPa and a high specific flexural strength (strength normalized by density) of over 350 MPa/(g cm−3) – both exceeding those of most other bulk magnesium (and magnesium alloys), ceramics, and their composite materials – as well as high damping capacities and good fracture toughness. The architectural design strategy and the robust fabrication approach may prove to be effective for developing new high-performance cermet materials. [ABSTRACT FROM AUTHOR]

Unidirectionally oriented architectures demonstrate a notable efficiency in enhancing the properties of macro-porous materials, yet are difficult to construct in a time- and cost-effective fashion. Here a facile approach was exploited for fabricating oriented macro-porous ceramic materials by employing natural graphite flakes as a fugitive material and preferentially aligning the flakes within ceramic matrices using accumulative rolling technique. Flaky to near-ellipsoid shaped pores with a homogeneous distribution were created in macro-porous zirconia ceramics with their porosity and microstructural characteristics adjustable by controlling the additive amounts of graphite flakes. The resulting materials exhibited a good combination of properties with high compressive strength up to over 1.5 GPa, which exceeds those of most other porous zirconia ceramics with similar porosities, along with low thermal conductivity of 0.92–1.85 Wm−1·K−1. This study offers a simple means for developing new oriented macro-porous materials with enhanced properties, and may promote their application by allowing for easy mass production. [ABSTRACT FROM AUTHOR]

Upon reducing the sample size into micrometer scale, an obvious brittle-to-ductile transition accompanied by a drastic change of failure mode from shattering to shear-banding was observed when compressing the brittle but strong Co 55 Ta 10 B 35 bulk metallic glass (BMG). The shattering failure under macroscopic compression is dominated by splitting cracking, which completely differs from shear-banding and originates from extrinsic defects like inclusions. To reveal the critical conditions for shear-banding and splitting cracking, various micropillar specimens with intentionally introduced holes as extrinsic defects were tested, and the stress distributions at the failure moment were analyzed with finite element simulation. The shear plane criterion was found to be quite effective to estimate the nominal stress required for the failure dominated by shear-banding. However, brittle splitting cracking does not occur although the maximum tensile stress reaches the critical value, which is different from traditional brittle solids. To initiate splitting cracking, a high-tensile-stress region over a critical distance, which depends on defect size and fracture toughness of the BMG, is required. The critical conditions for shear failure and splitting cracking demonstrated in this approach can be used to estimate the failure conditions of various BMG components with complex geometries in a wide range of length scales, and to design tough composites based on brittle BMGs. As an example, a design criterion to avoid brittle splitting fracture of porous BMG materials is proposed. Image 1 [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloy (RHEA) VNbMoTaW exhibits remarkably high strength in a much wide temperature range, whereas the brittle fracture behavior limits the applications. Here we show a significant size effect on the strength, plasticity and fracture behaviour of the VNbMoTaW RHEA. As sample size goes from millimeter to sub-micrometer scale, the brittle cracking behavior of the RHEA is greatly suppressed, along with a simultaneous enhancement of strength and plasticity. The improved mechanical properties can be attributed to the disappearance of crack initiation sites, the size-dependent dislocation plasticity at small length scale and the size-dependent competition in thermodynamics driving-force for cleavage cracking and plastic yielding. The results imply a promising potential of the RHEA for making microscale devices with high temperature environment. • Significant size effects on mechanical behaviors of RHEA were observed. • In microscale samples, brittle cracking behavior is greatly suppressed. • A size-induced simultaneous enhancement of strength and plasticity is found. • The crack initiation mechanisms of the brittle RHEA under compression were summarized. [ABSTRACT FROM AUTHOR]

The Al–Mg–Si alloy wire for overhead transmission line is in thermal service due to the interaction between electric current and microstructure during power transmission, which could affect its microstructure and properties. At present, researchers generally use the traditional annealed-heated (A-H) treatment to simulate the thermal service state of Al–Mg–Si alloy wire, which could not consider the additional effect of electrons on the microstructure and properties. Therefore, in this research, the Al–Mg–Si alloy wire was treated at various temperatures generated by the electric-heated (E-H) treatment using an electric current input device. The mechanisms behind the evolution of microstructures, strength and electrical conductivity of the E-H Al–Mg–Si alloy wire were revealed and compared with those of the A-H Al–Mg–Si alloy wire. The experimental results show that with increasing the E-H temperature of the Al–Mg–Si alloy, its strength decreased and the electrical conductivity increased, which may be attributed to the growth of radial grains and the coarsening of precipitates. In addition, the effect of E-H treatment on Al–Mg–Si alloy wire is different in various temperature ranges. In the low-temperature region (90 °C–110 °C) and the high-temperature region (200 °C), the strength and the electrical conductivity of the E-H and A-H Al–Mg–Si alloy wires are nearly the same. In contrast, in the medium-temperature region (160 °C–185 °C), the E-H Al–Mg–Si alloy wire has lower strength and higher electrical conductivity than the A-H Al–Mg–Si alloy wire, which is mainly due to the accelerated coarsening of precipitates caused by the local overheating around precipitates generated by the input electric current. • Electrothermal service state of Al alloy wire was simulated by experimental design. • Electric-heated Al alloy wire has lower strength and higher electrical conductivity. • Electric-heated treatment accelerates the coarsening of precipitate due to Joule heat. [ABSTRACT FROM AUTHOR]

A simple exponential strain hardening model (ESH) has been developed in the framework of the Kocks-Mecking-Estrin formalism with a new microstructure-based parameter that accounts for the effect of yield strength. The relevant parameters reflecting the effect of the composition (or dislocation annihilation distance) and the microstructure type (or strengthening technology) are comprehensively analyzed. The application scope of the model is then briefly discussed, and several significant advantages are enumerated including the clear derivation processes and the explicit physical meaning of the various parameters. Finally, the ESH model is verified extensively by systematic tensile tests on six groups of Cu-Al alloys having more than one hundred microstructural states. In addition, significant and quantitative revelations of strength and uniform elongation for ductile metals are elaborated in the following manuscript. The present ESH model is of significant theoretical value in providing a detailed understanding of the tensile performance of metallic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

An exponential strain-hardening (ESH) model for single phase metals was established and well verified by systematic experiments on Cu-Al alloys in an earlier study. In this report, several additional significant revelations will be documented for the tensile behaviors of several typical metals. Firstly, a unified interpretation of the well-known five strain-hardening stages is developed by correlating the characteristics of each stage with the parameter n that relates to the dislocation annihilation behavior. Secondly, quantitative relationships among the yield strength (YS), ultimate tensile strength (UTS) and uniform elongation (UE) are established and verified using the tensile experimental results for Cu-Al alloys. Thirdly, the two general principles of the synchronous improvement of strength and uniform elongation (SISUE) effect, such as the composition adjustment and microstructure optimization, are quantitatively revealed by the composition parameter n and a microstructure type parameter η. Two typical trends of the true UTS-UE curves and two kinds of characteristic strengths are quantitatively revealed and confirmed by the relevant experimental data. Finally, a prediction model of tensile properties is proposed and a corresponding procedure is displayed, which is further verified by the tensile experimental results for Cu-Al alloys. These applications further support the validity and significance of the ESH model. [Display omitted] [ABSTRACT FROM AUTHOR]