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This work proposes an effective design of bioactive 3D-printed Ti-6Al-4V scaffold with the CaO-MgO-SiO 2 glass-ceramic coating to realize a comparable elastic modulus of bone tissue and boost osteogenic differentiation. The improved elastic modulus and stiffness of Ti alloy were achieved via effectively increasing surface area of Ti alloy to reduce stress shielding effect. A hydrophilic surface and bioactive glass-ceramic coating were conducted via chemical etching and heat-treatment under argon atmosphere to enhance cells attachment and boost cell proliferation and osteogenic differentiation. The expression of osteogenic genes in bioactive CaO-MgO-SiO 2 glass-ceramic was evaluated through ALP, OPN, Runx2, and Col1A1 gene markers to explore the mechanism of superior osteogenic differentiation. Significant increase in OPN expression level confirmed the effect of CaO-MgO-SiO 2 coating for the enhancement of osteogenic bioactivity. This work provides a feasible approach through surface etching and bioactive CaO-MgO-SiO 2 glass-ceramic coating on the Ti alloy surface to enhance bioactivity and osteogenesis. [Display omitted] • A compatible bone tissue of 3D-printed Ti-6Al-4V scaffold with the novel bioactive CaO-MgO-SiO 2 glass-ceramic coating. • A superior surface modification to enhance cells attachment and boost cell proliferation and osteogenic differentiation. • This work provides a feasible approach on the Ti-alloy surface to enhance bioactivity and osteogenesis. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO) treatment has been performed on AZ91 Mg alloy in a silicate-containing alkaline electrolyte to disclose the relationship between second phase and resultant coating. The morphology and corrosion behavior were characterized for PEO coatings on three different AZ91 substrates with microstructures altered by heat treatment. In the presence of β phase, both the substrate and PEO coating exhibit enhanced corrosion resistance with finer and more evenly distributed β phase precipitates. In the as-cast AZ91, the anodized coating displays chemically and morphologically discontinuity on α and β phase with very coarse and defective regions on two-phase boundaries. In aged AZ91 with nano-sized β phase precipitates, the PEO coating shows no obvious difference on two-phase boundaries and is more homogenous with fewer pores and defects. The residual stress values given by X-ray diffraction (XRD) analysis indicate that PEO coating on aged AZ91 with finest β phase has the smallest stress which might be the reason for its improved corrosion resistance under synergetic effect of corrosive ions and residual stress. Conversely, in the absence of β phase, i.e. after solid solution treatment, the coating is characterized by the most inhomogeneous microstructure and the worst corrosion resistance, presumably owing to the absence of protective aluminum-containing oxides in the coating and more severe localized oxidation behavior adjacent to AlMn phase. Understanding the effect of second phase on PEO coating will enable us to optimize porous oxide structures for improved corrosion resistance by properly altering the substrate microstructure. [ABSTRACT FROM AUTHOR]

• Both the tensile strength and plasticity of the CrMnFeCoNi high-entropy alloy were enhanced significantly at high strain rates. • High strain rate embrittlement effect of CrMnFeCoNi high-entropy alloy is suppressed. • Cooperation of twins and dislocations is the crucial mechanism for the synchronous enhancement of strength and plasticity in this alloy under dynamic tension. • A thermo-viscoplastic dynamic constitutive model based on dislocation and twin evolution was developed. High-entropy alloys (HEAs), recently emerging alloy materials with numerous excellent performances, may have a wide application prospect in impact engineering. However, previous research regarding the mechanical behavior of HEAs has primarily focused on quasi-static testing, whereas the dynamic mechanical behavior of HEAs at high strain rates remains elusive. In this paper, the unusual simultaneous strength-plasticity enhancement and the inhibition of the high strain rate embrittlement of CrMnFeCoNi HEA in impact tension were revealed via split Hopkinson tensile bar (SHTB) with high-speed photography. Quantitative microstructural analysis indicates that the cooperation of twins and dislocations is the crucial mechanism for the synchronous enhancement of strength-plasticity in this alloy under impact tension. A thermo-viscoplastic constitutive model based on dislocations and twins evolution was developed to describe dynamic mechanical behavior. The high plastic hardening under dynamic tension was revealed to be induced by high dislocation forest hardening and strong resistance of twins to dislocation motion. The excellent combination of dynamic strength-plasticity of CrMnFeCoNi HEA makes it becoming a promising candidate for impact engineering applications. [ABSTRACT FROM AUTHOR]

Quasicrystals have been used in various applications to improve wear resistance as well as friction. It is known that quasicrystal (i-phase) content and microstructure in alloys have a decisive effect on the mechanical properties and tribological performance. In this research, four (β + i)-dual-phased quasicrystal alloys with different i-phase content and grain size were developed to alleviate the brittleness of the i-phase with the help of the soft β-phase. The influences of the i-phase content and grain size were investigated through impact test, wear test, and analysis. Through the annealing process, the amount of the i-phase was increased by about 38% (59.24% → 81.75%), and, besides, the grain size of the i-phase was simultaneously increased from 3.47 μm up to 9.98 μm. As the amount of i-phase increased, it was possible to increase the hardness from 712 HV to 763 HV. Meanwhile, the increased grain size (i-phase) reduced the contact stress of the grain during wear testing; thus, the specific wear rate could be decreased from 2.21 × 10−4 mm3/Nm to 0.5 × 10−4 mm3/Nm. Not only that, but an experimental wear equation was obtained using empirical data to predict the wear behavior of the dual-phased alloys. Design of dual-phased quasicrystal alloys with different i-phase content; 59.24% (0 h), 68.85% (12h), 75.84% (24 h), and 81.75% (36 h) under a 600 °C annealing process. The higher content of i-phase in quasicrystal alloy shows a favorable tribological behavior because of the microstructure and mechanical properties of the dominant i-phase. Unlabelled Image • Dual-phased quasicrystal alloys were developed by a simple processing procedure. • The wear resistance is enhanced according to the increase of the i-phase. • The ductile beta-phase in dual-phase quasicrystal alloys reduces the cracking. • The optimal concentration of the two phases was found for the best tribological performance. [ABSTRACT FROM AUTHOR]

• Developed biodegradable magnesium-based alloy skull repairment (MASR) for skull bone defect. • The Mg-2Zn alloy-based MASR presented a lower degradation rate, greater mechanical strength, and less influence on bone structure. • Revealed the close interaction of MASR and intracranial microenvironment. Over the last decade, due to the disadvantages of conventional implant materials in skull bone defects, there has been a high demand for alternative biodegradable materials. As a typical biodegradable metal, magnesium (Mg) and its alloy have been successfully researched in various fields and applied in clinical in recent years, but none of them are about osteointegration, especially in cranioplasty. This study aims to explore the effect of Mg-based alloy skull repairment (MASR) on bone healing for the first time. The results verify that the high pure magnesium (HPM) and Mg-2 wt% Zn alloys can promote skull bone repair and induce the M2-like polarization of macrophages. Meanwhile, we also confirmed the pro-osteogenic function of induced M2-like macrophages on the bone marrow stem cells. Moreover, due to the close interaction of MASR and intracranial microenvironment, we clarified its immune regulatory function and underlying mechanisms on the microglia. The Mg-2Zn alloy presented a lower degradation rate, greater mechanical strength, and less influence on bone structure, and the MASR may serve as a potential clinical approach. [ABSTRACT FROM AUTHOR]

Metallic wires with high strength-ductility at both room and cryogenic temperatures are always pursued for engineering applications. However, traditional metallic wires are tortured inevitably by strength-ductility trade-off dilemma. In this work, a gradient heterogeneous lamella structure, characterized with hard gradient-distributed B2 lamellae embedded in soft FCC lamellae matrix, is introduced into AlCoCrFeNi 2.1 eutectic high entropy alloy (EHEA) wire by well-designed multiple-stage heavy-drawn and heat treatment processes, which achieves an outstanding strength-ductility synergy. This EHEA wire exhibits not only high tensile strength of 1.85 GPa and sufficient uniform elongation of ∼12% at room temperature, but also ultra-high tensile strength of 2.52 GPa and even slightly elevated uniform elongation of ∼14% at cryogenic temperature. In-depth microstructure characterization indicates that the gradient heterogeneous lamella structure facilitates a radial gradient distribution of geometrically necessary dislocation (GND) during tension, i.e., the GND density decreases gradually from the surface region to the central region of EHEA wire, which induces pronounced strain gradient strengthening effect and thus greatly benefits the mechanical properties. Intriguingly, at cryogenic temperature, dense cross-slip which gives rise to intensively dynamic microstructure refinement is firstly observed in the B2 phase of EHEA wire. The activation of cross-slip provides sufficient ductility while inducing evidently dynamic Hall-Petch effect, becoming the most effective deformation mechanism contributing to the unprecedented cryogenic tension properties. This work sheds light on designing ultra-strong EHEA wire and other advanced metallic wires. [Display omitted] [ABSTRACT FROM AUTHOR]

Fatigue properties are essential for structural materials in industrial applications. High-entropy alloys are promising fatigue-resistant alloys with high strengths and good ductilities. In this study, the B2 precipitate significantly increased the yield strength of the Al 0.3 CoCrFeNi high-entropy alloy but at the same time decreased the low-cycle fatigue life. A detailed investigation of the underlying mechanisms will provide critical insights into the precipitate effect on the fatigue performance of high-entropy alloys. Here, the Al 0.3 CoCrFeNi alloys with single face-centered-cubic (FCC) phase and with FCC + B2 phases are used for the investigation of the low-cycle fatigue behavior by combining in situ neutron diffraction measurements and elastic-viscoplastic self-consistent modeling. The simulation results indicate that the B2 precipitates highly increased the back stresses during cyclic loading by facilitating the kinematic hardening in the matrix, while the effect of dynamic recovery is relatively weak. The increase in back stresses provides more fatigue-crack-initiation sites and thus the damage accumulation, which will further lead to a shorter fatigue life. [Display omitted] • The B2 precipitates increased the yield strength and decrease the LCF life in the Al 0.3 CoCrFeNi HEA. • Lattice strain and full-width half-maximum results were obtained from in situ neutron diffraction. • Diffraction experiments and crystal plasticity modeling reveal the role played by B2 precipitates. [ABSTRACT FROM AUTHOR]

• The radii of the nanoscale precipitates are dramatically smaller in the annealed Cu-2Ag-0.14La alloy than in the annealed Cu-2Ag alloy. • The grain size of annealed Cu-2Ag-0.14La alloy is always smaller than that of the annealed Cu-2Ag alloy from 400 °C to 650 °C. • Precipitation strengthening of nanoscale precipitates in the matrix and grain-boundary strengthening during grain refinement substantially improve the yield strength of the Cu-2Ag-0.14La alloy. [Display omitted] A new Cu–2Ag–0.14La alloy is developed to enhance the mechanical property and electrical conductivity with inducement of Ag-rich primary phases and finer nanoscale Ag precipitates. The microstructural evolution and mechanical properties of Cu–2Ag–0.14La and Cu–2Ag alloys obtained by drawing and annealing were then summarized and analyzed. The results indicate that both the yielding and ultimate tensile strengths of annealed Cu–2Ag-0.14La alloy were reinforced after La modification. The average grain sizes of two alloys increase during annealing, but the size ratio (R Cu-2Ag-0.14La /R Cu-2Ag) dramatically varies with rising the heat temperature, evolving from 70.48% at 400 °C to 43.78% at 650 °C. Meanwhile, it is found that the refined grains sizes in Cu-2Ag-0.14La alloy are closely related to the nano-scale precipitates (~450 nm), which hinder the formation of subgrain boundaries at 400 °C, and impose a stronger pinning effect on boundary migration of recrystallized grains during annealing (≥ 450 °C). Consequently, higher hardness and electrical conductivity are contributed by grain refinement and dispersion strengthening of the nanosized phases. [ABSTRACT FROM AUTHOR]

Low thermal expansion alloy plays a unique role in high precision instruments and devices owing to its size stability under thermal shocks. However, a low thermal expansion generally produces a poor mechanical performance, such as brittleness and low fracture resistance, which is a bottle-neck for their applications as functional materials. Here, we demonstrate a novel intermetallic compound-based dual-phase alloy of Er-Fe-V-Mo with excellent structural and functional integrity achieved by precipitating a ductile phase in the hard-intermetallic matrix with large magnetovolume effect. It is found that the compound with 12.8 ± 0.1vol% precipitate phase improves the alloy's strength and toughness by one order of magnitude, while keeping a low bulk coefficient of thermal expansion (1.87±0.02 × 10−6 K −1) over a wide temperature range (100 to 493 K). The combined analyses of real-time in-situ neutron diffraction, synchrotron X-ray diffraction, and microscopy reveal that both the thermal expansion and the mechanical properties of the precipitate phase are coupled with the matrix phase via semi-coherent interfacial constraint; more importantly, the precipitate phase undergoes a pronounced strain hardening with dislocation slips, which relieves the stress localization and thus hinders the microcrack propagation in the intermetallic matrix. Moreover, the alloys are easy to fabricate and stable during thermal cycling with great application potentials. This study shed light on the development of low thermal expansion alloys as well as the implications to other high-performance intermetallic-compound-based material design. Image, graphical abstract [ABSTRACT FROM AUTHOR]

"Self-sharpening", a material maintaining its acute head shape during penetration, is highly desirable in a wide range of engineering applications. However, it remains a great challenge to make it occur in conventional single-principal-element alloys. Here, we develop a new chemical-disordered multi-phase tungsten high-entropy alloy that exhibits outstanding self-sharpening capability, in sharp contrast to conventional tungsten alloys only showing mushrooming. This alloy consists of a BCC dendrite phase and a rhombohedral μ phase embedded in the continuous FCC matrix, and such a unique microstructure leads to a 10–20% better penetration performance than conventional tungsten heavy alloys. We show that emergence of the self-sharpening is triggered by the ultrastrong μ phase stimulated dynamic recrystallization softening mediated shear banding. This study sheds light on the origin of self-sharpening and might open new opportunities for developing high-performance penetrator materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlights • Sodium dodecyl sulphate (SDS) is found to be an efficient Mg corrosion inhibitor. • Inhibitors are adsorbed on AlMn intermetallics to suppress micro-galvanic corrosion. • Large amounts of inhibitors are physically adsorbed on corroded α-Mg region. • A passive hydrophobic corrosion layer is formed to kinetically inhibit corrosion. • Adsorption of SDS on Mg surface follows Langmuir adsorption isotherm. Abstract The inhibition mechanism of a high-efficiency corrosion inhibitor (sodium dodecyl sulfate, SDS) is unveiled and the strategy to design effective inhibitors for Mg alloys is suggested. It was found that SDS is chemically absorbed on the cathodic intermetallics to inhibit micro-galvanic corrosion. Anodic Mg dissolution is also kinetically suppressed by physisorption of SDS since the long hydrophobic tail of the surfactant contributes to building up a protective corrosion layer. Utilization and synthesis of such green inhibitors can pave the way for a wider range of applications for Mg alloy and provide active corrosion protection for coated Mg surfaces. [ABSTRACT FROM AUTHOR]

The cyclic stability of hydrogen absorption and desorption is an important indicator of hydrogen storage alloy. The decay mechanism was roundly investigated by controlling the depth of dehydrogenation (DOD) of the V 40 Ti 25.5 Cr 26.5 Fe 8 alloy during the process of hydrogen ab/desorption cycles. The V 40 Ti 25.5 Cr 26.5 Fe 8 alloy exhibits the hydrogen desorption capacity of 2.36 wt% at 323 K in the first cycle. After 30 cycles, the decay rate of the hydrogen desorption capacity is only 4.37 % at 40 % DOD, but rises to 8.74 % at 100 % DOD. The hydrogen desorption capacity (C), plateau pressure (P) and micro-strains (S) all show an "acceleration followed by slowing" exponential variation trend with the increase of cycle number (x). Additionally, any two of C , P and S show linear correlation. It is considered that the micro-strains in the crystal lattice is the main factor for the decay of the hydrogen desorption capacity and the plateau pressure. On the premise of ensuring the valid hydrogen storage capacity to meet the requirements of the application, properly reducing DOD per cycle can effectively reduce the micro-strains accumulation and cell volume expansion, thus improving the cyclic stability of the alloy. Moreover, the application of this alloy in a fuel cell bicycle was investigated, and the total range and mileage per unit weight of the alloy are up to 100.8 km and 15.7 km/kg, respectively. Compared with the lead-acid battery, lithium-ion battery and LaNi 5 -based hydrogen fuel cell, the V-Ti-Cr-Fe-based fuel cell shows significant advantages. ● A bran-new method was proposed to slow down the decay of the dehydrogenation capacity of the V 40 Ti 25.5 Cr 26.5 Fe 8 alloy. ● The alloy decay rate of the dehydrogenation capacity is only 4.37% after 30 cycles at 40% DOD, only half that at 100% DOD. ● Six functions were proposed to explain the influences of the micro-strains in the lattice. ● This alloy fuel cell shows significant advantages compared with other batteries through application in a fuel cell bicycle. [ABSTRACT FROM AUTHOR]

CoCrFeMnNi high-entropy alloys (HEAs) are additively manufactured by laser directed energy deposition (L-DED) and laser powder bed fusion (L-PBF) processes. Comparative studies are conducted for the microstructures and deformation mechanisms of L -DED and L -PBF samples. In both types of samples, highly heterogeneous microstructures are formed, consisting of columnar grains, solidification cells, and dislocation networks. However, substantial differences are measured in the crystallographic texture, cell size, and elemental distribution. Deeper melt pools in the L -DED samples promote a mixed crystallographic texture of <101>/<111> as opposed to <001> along the build direction in the L -PBF samples. The <101>/<111> texture elevates the flow stresses and facilitates the activation of deformation twins in the L -DED samples. Moreover, their larger solidification cell sizes and associated chemical segregation across cell walls increase the dislocation storage capability and resistance to dislocation motion, leading to profuse planar slip bands and microbands during plastic deformation. The enhanced plastic deformation capabilities in the L -DED samples give rise to more sustained strain hardening and thus higher ductility compared to the L -PBF samples. Our work not only provides fundamental insights into the deformation mechanisms of additively manufactured HEAs, but also underscores the critical impact of processing conditions on the solidification microstructure and material design by additive manufacturing. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Adding the Cu led to the formation of Cr-enriched precipitates in the matrix. • The Cr 7 C 3 precipitate in the CoCrMo-4Cu was partially coherent with Cu nanoparticle. • The Cr-enriched precipitates were the critical contributor to enhancing the tribology property. • The corrosion resistance of CoCrMo alloy was enhanced as the 2 and 3 wt% Cu added into CoCrMo alloy. In this study, the cobalt-chromium-molybdenum (CoCrMo) alloys containing varying Cu contents (CCM- x Cu, x = 0, 2, 3, 4 wt%) were fabricated via the selected laser melting (SLM) method. The influences of Cu content on tribological performance and corrosion resistance were investigated. The 2 and 3 wt% Cu contributed to inhibiting the generation of the HCP phase, whereas the inhibitory effect was quite limited at 4 wt% Cu. Notably, 4 wt% Cu led to the formation of Cr-enrich precipitates in the matrix, which was partially coherent with the Cu nanoparticle. The corrosion resistance of the CCM alloy was enhanced as the 2 and 3 wt% Cu added into the CCM alloy, contrarily, which deteriorated when Cu content reached 4 wt%. For the CCM-2Cu and CCM-3Cu, Cr-precipitates played a major role in enhancing the wear resistance, while the Cu lubrication effect working in coordination with Cr-precipitates determined that for the CCM-4Cu. This study was expected to achieve better tribology and corrosion properties of SLM-produced CCM alloys by tailoring microstructure through the Cu element. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ neutron diffraction measured the elastic properties of NbV, NbTiV, and MoNbV alloys, which are consistent with first-principles calculations. • Adding Ti elements into the NbV alloy results in the formation of the elastically isotropic NbTiV alloy. • This work provides valuable insights into the design of ductile and strong refractory high-entropy alloys by tuning the elastic properties. Elastic properties are essential to the mechanical performance of materials, and therefore, can be tuned to design high-performance materials. In this study, the elastic constants of the equiatomic ternary refractory multi-principal-element alloys, NbTiV, and MoNbV, were investigated, using in-situ neutron diffraction and first-principles calculations. The experimentally measured and theoretically predicted elastic constants show a good agreement. The alloying effect of adding Ti and Mo into NbV base alloy on the elastic constants is studied. Particularly, adding Ti elements into the NbV alloy results in the increase of the Zener anisotropy ratio from 0.59 to 0.99, leading to the formation of the elastically isotropic NbTiV alloy, while the addition of Mo decreases the anisotropy ratio to 0.52. Pugh's ratio (B / G), Cauchy pressure (C 12 - C 44), and Poisson's ratio (ν) are used to predict the brittle/ductile nature of the studied alloys, which is consistent with the mechanical results. The present work provides valuable insights into the design of ductile and strong refractory high-entropy alloys by tuning the elastic properties. [ABSTRACT FROM AUTHOR]

• Microstructural evolution analysis for V-5Cr-5Ti alloy is conducted. • A physically-based strain hardening model for V-5Cr-5Ti alloy is developed. • Flow stress rule and dislocation density evolution equations are characterized. • The validity and applicability are examined by comparison studies. V-5Cr-5Ti alloy is a promising candidate structural material for fusion-power reactor blankets. However, its plastic deformation behavior, which is important to the safety and reliability of a fusion reactor, is not sufficiently understood. The present paper develops a physically based strain hardening model to characterize the plastic deformation of V-5Cr-5Ti alloy. Using miniaturized specimens of V-5Cr-5Ti alloy, uniaxial tensile tests and microstructural evolution analysis are performed at different strain levels. Microstructural evolution results show that the existence of Ti-enriched second phase and the dislocation interactions are critical to the plastic deformation of V-5Cr-5Ti alloy. On the above physical basis, the Ti-enriched second phase and the evolution equations of the dislocation density are developed, while the flow stress rule is formulated from the summation of athermal stress, thermally activation stress, and dispersed-phase stress. The finite element method based on the user-material subroutine UMAT (User-defined Material Mechanical Behavior) of commercial ABAQUS code (finite element analysis software) and the implicit stress update algorithm are adopted to realize the proposed physically based strain hardening model. Results suggest that this new strain hardening model is superior to conventional models for providing a more accurate and reasonable prediction of the plastic deformation behavior of V-5Cr-5Ti alloy. [ABSTRACT FROM AUTHOR]