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• The effect of precold deformation on precipitation behavior was studied. • The thermal treatment parameters were optimized and dual aging process was customized. • High-density L1 2 nanoprecipitates were induced in the 65 % precold deformed HEA. • Compared with the solid solution HEA, the YS of the DA-HEA increased by 1657 MPa, possessing an astonishing increase of ∼440 %. How to achieve high-entropy alloys (HEAs) with ultrahigh strength and ductility is a challenging issue. Precipitation strengthening is one of the methods to significantly enhance strength, but unfortunately, ductility will be lost. To overcome the strength–ductility trade-off, the strategy of this study is to induce the formation of high-density nanoprecipitates through dual aging (DA), triggering multiple deformation mechanisms, to obtain HEAs with ultrahigh strength and ductility. First, the effect of precold deformation on precipitation behavior was studied using Ni 35 (CoFe) 55 V 5 Nb 5 (at.%) HEA as the object. The results reveal that the activation energy of recrystallization is 112.2 kJ/mol. As the precold-deformation amount increases from 15 % to 65 %, the activation energy of precipitation gradually decreases from 178.8 to 159.7 kJ/mol. The precipitation time shortens, the size of the nanoprecipitate decreases, and the density increases. Subsequently, the thermal treatment parameters were optimized, and the DA process was customized based on the effect of precold deformation on precipitation behavior. High-density L1 2 nanoprecipitates (∼3.21 × 1025 m−3) were induced in the 65 % precold-deformed HEA, which led to the simultaneous formation of twins and stacking fault (SF) networks during deformation. The yield strength (YS), ultimate tensile strength, and ductility of the DA-HEA are ∼2.0 GPa, ∼2.2 GPa, and ∼12.3 %, respectively. Compared with the solid solution HEA, the YS of the DA-HEA increased by 1,657 MPa, possessing an astonishing increase of ∼440 %. The high YS stems from the precipitation strengthening contributed by the L1 2 nanoprecipitates and the dislocation strengthening contributed by precold deformation. The synergistically enhanced ductility stems from the high strain-hardening ability under the dual support of twinning-induced plasticity and SF-induced plasticity. [Display omitted] [ABSTRACT FROM AUTHOR]

Gradient structured metallic materials are attracting increasing attention because of their excellent properties. However, with existing manufacturing techniques, most reported gradient structures are limited to the near-surface regions or sample-level. Approaches are needed to prepare large metallic workpieces with throughout gradient microstructures for engineering applications. This work utilizes the characteristics of non-uniform deformation along the thickness direction of power spinning to manufacture high-Mn steel tubes with gradient nanotwins structures. The composition of high-Mn austenitic steel was carefully designed to make the twinning behavior sensitive to changes in strain. Specifically, the twin probability increases from 0.13 % in the innermost layer to 0.49 % in the outermost layer and the corresponding average twin boundary spacing decreases from 154.5 nm to 47.3 nm. The density of nanotwins presents a gradient, while the grain size and geometrically necessary dislocation density are nearly unchanged. A gradient distribution of hardness is obtained along the thickness direction of the tube with the gradient nanotwin structures. The hardness continuously increases from 3.32 GPa to 5.45 GPa distributed over a wall thickness of 8.5 mm. This work proposed a potential way combining material designing and power spinning for manufacturing large rod/tube-liked workpieces with throughout gradient nanotwins.

• The CR95 RHEA forms heterogeneous structure by severe plastic deformation. • The CR95 RHEA possesses the highest tensile strength among RHEAs. • HDI hardening accounts for ultra-high strength in the CR95 RHEA. • The MBIP effect contribute the CR95–850 alloy an excellent tensile ductility. Refractory high-entropy alloys (RHEAs) are potential materials for high-temperature structural applications due to their excellent high-temperature performance. However, the early onset of plastic instability in RHEAs is a critical issue to be addressed. In this study, a novel Zr 35 Ti 30 Nb 20 Al 10 V 5 RHEA was subjected to 95% cold rolling and annealing, achieving outstanding mechanical properties. Notably, the cold-rolled alloy exhibited the highest reported tensile strength (∼2.0 GPa) among RHEAs with a moderate ductility of ∼8.5%. Moreover, Additionally, the subsequent annealing process enabled the alloy to achieve an outstanding combination of yield strength (1.1 GPa) and fracture elongation (20%). The cold-rolled alloy has a heterogeneous lamella structure with high-density dislocation cells and dislocation pile-ups, and lattice distortion in the locally chemically ordered structure. The high work hardening behavior originates from the heterogeneous deformation-induced (HDI) hardening, which makes the HDI stress and hardening rate increase with increasing strain. In the annealed alloy, lattice distortion increases significantly with increasing strain, promoting dislocation cross-slip. The dislocation pile-ups and interactions facilitate the transition of microbands, and the relatively stable work-hardening behavior of the alloy is mainly attributed to the microband-induced plasticity effect. This study provides novel insights into the design and optimization of highly formable RHEAs with excellent mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

• Enhanced strength–ductility synergy has been achieved in a Fe Mn C V steel via tuning stacking-fault energy by precipitation. • Precipitation of V-carbides is selected to tune the global stacking-fault energy of the matrix, making tactful use of interstitial element carbon. • Strong work-hardening due to low SFE and fine matrix/twin lamellae provide the good ductility while strengthened by precipitation, achieving the strength–ductility synergy. Deformation-induced twinning or martensitic transformation can improve the work-hardening capability of alloys with face-centered cubic (FCC) structures and suppress strain localization. The stacking fault energy (SFE) of alloys plays a key role in determining deformation mechanisms and mechanical properties. This study developed V-bearing high-Mn steel with a tensile strength of 1288 MPa and uniform elongation of 36 % by tactfully designing the composition. Precipitation of V-carbides was selected to strengthen the steel and tune the global SFE of the matrix by settling carbon. Stronger work-hardening capability due to lower SFE and finer twin/matrix lamellae provided the steel with good ductility, while precipitation strengthened it. [Display omitted] [ABSTRACT FROM AUTHOR]

Global warming is causing melting of glaciers, which is affecting socioeconomic development. It is essential to study the combined influence of changes in structures of glaciers on human well-being and socioeconomic systems. Herein, we considered Qilian Mountains as an example, quantified the regional socioeconomic benefits of glaciers and human well-being, and attempted to draw a correlation between glacier service value and human well-being. The findings of our study reveal that the value of glacier services in Qilian Mountains decreased from 1.84 × 1010yuan in 1998 to 1.72 × 1010yuan in 2018, with a spatial trend of circling down from the central region to the western and eastern regions. The distribution of human well-being showed an increasing trend, and a phenomenon of “low value central and western clustering, high value eastern sporadic distribution.” There is an increasing degree of coordination between human well-being and glacier services value; the spatial distribution shows a decreasing trend from the west to the east, with differences in the nature of coordinated development in different regions at the same coordination stage being obvious. We analyzed the changes in glacier services value and their relationship with human well-being from both micro and macro perspectives to provide theoretical support for formulating management strategies for glacier resource conservation and improving the interface between glacier service evaluation results and government decision-making.

Precipitation strengthening can effectively improve the strength of high entropy alloys (HEAs), but usually severely reduces the ductility. In this study, a new interstitial carbon-doped HEA with a nominal composition of Ni33.5(CoFe)55V5Nb5C1.5at.% was developed. The HEA exhibits a high yield strength of 1244 MPa, ultimate tensile strength of 1553 MPa and excellent elongation of ~ 30%. The stacking fault energy of the matrix is affected by the precipitation of L12-Ni3Nb, which enhances the stacking fault (SF)-induced deformation. Since the Taylor lattice domains are subdivided by the SF networks, the mean free path of dislocation is reduced. The enhanced strain-hardening ability leads to a good combination of strength and ductility.

Polycrystalline FeMnAlNi-based alloys generally exhibit poor pseudoelasticity owing to grain constraint. A promising method to improve the pseudoelasticity involves increasing the grain size by directional recrystallisation (DR). To improve the efficiency of obtaining large grain size, the effect of DR parameters—hot zone temperature (HZT) and drawing velocity—on the columnar grain size and the mechanisms of grain growth were investigated. The results showed that samples of FeMnAlNiCo shape memory alloys (SMAs) with an average grain size of over 20 mm and the largest grain size exceeding 50 mm were obtained after DR. The apparent activation energy of the columnar grain growth for DR was ≈135 kJ/mol, which was much lower than that of the equiaxed grain growth for isothermal annealing (≈384 kJ/mol). The lateral growth of the columnar grains was probably because the boundaries between columnar grains tend to form random high-angle grain (HAG) boundaries. By incremental compression test, at an applied strain of 7.0%, nearly <104> oriented single crystal exhibited a recoverable strain of ≈6.0%, while the polycrystal had a recoverable strain of only ≈3.4%. This work provides important guidance and inspires new strategies for microstructural control in FeMnAlNi-based SMAs.

AbstractGas explosions and outbursts were the leading types of gas accidents in mining in China with gas concentration exceeding the threshold limit value (TLV) as the leading cause. Current research is focused mainly on using machine learning approaches for avoiding exceeding the TLV of the gas concentration. no published reports were found in the literature of attempts to uncover the correlation between gas data and other data to predict gas concentration. This research aimed to fill this gap and develop an innovative gas warning system for increasing coal mining safety. A mixed qualitative and quantitative research methodology was adopted, including a case study and correlational research. This research found that strong correlations exist between gas, temperature, and wind. It suggests that integrating correlation analysis of data on temperature and wind into gas would improve warning systems' sensitivity and reduce the incidence of explosions and other adverse events. A Unified Modeling Language (UML) model was developed by integrating the Correlation Analysis Theoretical Framework to the existing gas monitoring system for demonstrating an innovative gas warning system. Feasibility verification studies were conducted to verify the proposed method. This informed the development of an Innovative Integrated Gas Warning System which was deployed for user acceptance testing in 2020.

The thermal stability of Al-RE(rare earth) intermetallic phases with individual REfor heat-resistant high-pressure die-casting Mg–Al–REalloys is investigated. The results of this study show that the main strengthening phase of Mg-4Al-4Ce alloy is Al11Ce3, whose content is about 5 wt.% according to quantitative X-ray diffraction phase analysis. The Al11Ce3phase appears to have high thermal stability at 200 °C and 300 °C, while phase morphology change with no phase structure transition could occur for Al11Ce3when the temperature reaches 400 °C. Furthermore, besides the kinds of rare earths and temperature, stress is also an influencing factor in the microstructural stability of Mg-4Al-4Ce alloy.

A rare earth holmium (Ho) element was introduced into Mg-8Li-3Al alloy to investigate the effects of holmium and hot-rolling on the microstructure and mechanical properties of the Mg-Li based alloys. Both alloys with and without Ho showed a duplex structure with α and β phases. The as-cast Mg-8Li-3Al alloy exhibited a yield strength (YS) of 111.1 MPa, ultimate tensile strength (UTS) of 148.2 MPa and an elongation of 9.50% while the hot-rolled Mg-8Li-3Al-3Ho alloy had a yield strength of 249.7 MPa, ultimate tensile strength of 293.1 MPa with an elongation of 21.40%. These results indicated that both strength and ductility could be significantly enhanced by addition of holmium together with thermo-mechanical treatment. It was found that the microstructure could be refined significantly and the fracture modes changed from partial brittle to ductile fracture due to the addition of holmium. The effects of microstructure refinement, work hardening and solid solution strengthening induced by the addition of holmium and hot-rolling on the mechanical properties were discussed.

The optimal aging temperatures of 400 - 550 °C for high strength steels falls into the dangerous temperature range of temper-embrittlement. To obtain a good low-temperature toughness, temperatures above 600 °C are usually selected for aging treatments, resulting in a huge loss of strength. In this work, the effects of aging treatments at 500 and 550 °C on the impact performance of a Cu precipitation-strengthened steel at a low temperature of -80 °C were systematically investigated. The solute segregation at lath boundaries is found to be the main factor controlling the low-temperature toughness. Excellent impact performance of ∼180 J at -80 °C along with a high yield strength of ∼1050 MPa and a total elongation of 19% can be obtained by controlling the segregation of solute elements, specifically Mo and Mn at the lath boundaries. The evolutions of matrix and precipitates during aging treatments were investigated. The strengthening and toughening mechanisms are also critically discussed.

An ultrasonic-assisted method for electroless Ni-P plating on dual-phase Mg-Li alloy is proposed. Environmentally-friendly Ce(NO3)3-KMnO4 solution was successfully applied for the pre-treatment. Uniform and compact Ni-P coatings with fine structures have been successfully obtained. The Ni-P coatings are mixed with amorphous-crystalline features and well adhered to the substrates. The corrosion resistances were investigated by electrochemical impedance spectroscopy, open circuit potential, potentiodynamic polarization and hydrogen evolution tests. The results indicate that ultrasonic processing significantly improves the corrosion resistance of Ni-P coatings due to the formation of uniform, dense and fine structures, which strengthen the passive film.

Magnetoelastic biosensors have been studied for the past few years for use in detecting bacteria for food safety. These magnetoelastic biosensors are composed of a bio-molecular recognition element and transducer platform (magnetoelastic resonator). Phages (bio-molecular recognition element) have been developed to provide very specific binding with Salmonella typhimurium bacteria. However, there is some binding (non-specific binding) of bacteria to the gold areas not covered with phage on both the measurement and control sensors. In those areas, a blocking agent is necessary to reduce the non-specific binding. The purpose of this study is to compare three of the often used blocking agents, BSA, milk and casein in different concentrations to determine the agent and the optimum concentration for blocking. To accomplish this, a set of measurement and control sensors were prepared using identical procedures except the control sensors were not immobilized with phage. The measurement and control sensors were then coated with a blocking agent of concentrations ranging from 0.1 to 5 mg/mL. SEM observations show that coating the magnetoelastic biosensors with BSA at a concentration of 1mg/mL yields the largest amount of specific binding of bacteria cells while also maintaining the largest ratio of specific to non-specific binding. This binding characteristic is a result of the physical and electrical structure of the blocking proteins. To verify that the blocking solutions made good contact with the sensor's surface, contact angle measurements were used to evaluate the wettability of the surface. Changes in the resonant frequency of the biosensors were found to agree with the results from SEM observations.

An ultrasonic-assisted method for electroless Ni-P plating on dual-phase Mg-Li alloy is proposed. Environmentally-friendly Ce(NO3)3-KMnO4solution was successfully applied for the pre-treatment. Uniform and compact Ni-P coatings with fine structures have been successfully obtained. The Ni-P coatings are mixed with amorphous-crystalline features and well adhered to the substrates. The corrosion resistances were investigated by electrochemical impedance spectroscopy, open circuit potential, potentiodynamic polarization and hydrogen evolution tests. The results indicate that ultrasonic processing significantly improves the corrosion resistance of Ni-P coatings due to the formation of uniform, dense and fine structures, which strengthen the passive film.

Magnetoelastic biosensors have been studied for the past few years for use in detecting bacteria for food safety. These magnetoelastic biosensors are composed of a bio-molecular recognition element and transducer platform (magnetoelastic resonator). Phages (bio-molecular recognition element) have been developed to provide very specific binding with Salmonella typhimuriumbacteria. However, there is some binding (non-specific binding) of bacteria to the gold areas not covered with phage on both the measurement and control sensors. In those areas, a blocking agent is necessary to reduce the non-specific binding. The purpose of this study is to compare three of the often used blocking agents, BSA, milk and casein in different concentrations to determine the agent and the optimum concentration for blocking. To accomplish this, a set of measurement and control sensors were prepared using identical procedures except the control sensors were not immobilized with phage. The measurement and control sensors were then coated with a blocking agent of concentrations ranging from 0.1 to 5 mg/mL. SEM observations show that coating the magnetoelastic biosensors with BSA at a concentration of 1mg/mL yields the largest amount of specific binding of bacteria cells while also maintaining the largest ratio of specific to non-specific binding. This binding characteristic is a result of the physical and electrical structure of the blocking proteins. To verify that the blocking solutions made good contact with the sensor's surface, contact angle measurements were used to evaluate the wettability of the surface. Changes in the resonant frequency of the biosensors were found to agree with the results from SEM observations.