Role of micro-Ca/In alloying in tailoring the microstructural characteristics and discharge performance of dilute Mg-Bi-Sn-based alloys as anodes for Mg-air batteries

The influence of micro-Ca/In alloying on the microstructural charac teristics,electrochemical behaviors and discharge properties of extruded dilute Mg-0.5Bi-0.5Sn-based(wt.%)alloys as anodes for Mg-air batteries are evaluated.The grain size and texture intensity of the Mg-Bi-Sn-based alloys are significantly decreased after the Ca/In alloying,particularly for the In-containing alloy.Note that,in addition to nanoscale Mg_(3)Bi_(2)phase,a new microscale Mg_(2)Bi_(2)Ca phase forms in the Ca-containing alloy.The electrochemical test results demonstrate that Ca/In micro-alloying can enhance the electrochemical activity.Using In to alloy the Mg-Bi-Sn-based alloy is effective in restricting the cathodic hydrogen evolution(CHE)kinetics,leading to a low self-corrosion rate,while severe CHE occurred after Ca alloying.The micro-alloying of Ca/In to Mg-Bi-Sn-based alloy strongly deteriorates the compactness of discharge products film and mitigates the"chunk effect"(CE),hence the cell voltage,anodic efficiency as well as discharge capacity are greatly improved.The In-containing alloy exhibits outstanding discharge performance under the combined effect of the modified microstructure and discharge products,thus making it a potential anode material for primary Mg-air battery.

Mechanical behavior and response mechanism of porous metal structures manufactured by laser powder bed fusion under compressive loading

Al Si10Mg porous protective structure often produces different damage forms under compressive loading,and these damage modes affect its protective function.In order to well meet the service requirements,there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading.In this paper,Al Si10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact,strong-energy absorption,and lightweight characteristics.The mechanical behaviors of AlSi10Mg porous structures,including the stress-strain relationship,structural bearing state,deformation and damage modes,and energy absorption characteristics,were obtained through experimental studies at different loading rates.The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties.Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section,and the damage location is almost at 45°to the load direction,which is the most direct cause of its structural damage,revealing the damage mechanism of AlSi10Mg porous structures under the compressive load.The normalized energy absorption model constructed in the paper well interprets the energy absorption state of Al Si10Mg porous structures and gives the sensitive location of the structures,and the results of this paper provide important references for peers in structural design and optimization.

Phase-field simulation of lack-of-fusion defect and grain growth during laser powder bed fusion of Inconel 718

The anisotropy of the structure and properties caused by the strong epitaxial growth of grains during laser powder bed fusion(L-PBF)significantly affects the mechanical performance of Inconel 718 alloy components such as turbine disks.The defects(lack-of-fusion Lo F)in components processed via L-PBF are detrimental to the strength of the alloy.The purpose of this study is to investigate the effect of laser scanning parameters on the epitaxial grain growth and LoF formation in order to obtain the parameter space in which the microstructure is refined and LoF defect is suppressed.The temperature field of the molten pool and the epitaxial grain growth are simulated using a multiscale model combining the finite element method with the phase-field method.The LoF model is proposed to predict the formation of LoF defects resulting from insufficient melting during L-PBF.Defect mitigation and grain-structure control during L-PBF can be realized simultaneously in the model.The simulation shows the input laser energy density for the as-deposited structure with fine grains and without LoF defects varied from 55.0–62.5 J·mm^(-3)when the interlayer rotation angle was 0°–90°.The optimized process parameters(laser power of 280 W,scanning speed of 1160 mm·s^(-1),and rotation angle of 67°)were computationally screened.In these conditions,the average grain size was 7.0μm,and the ultimate tensile strength and yield strength at room temperature were(1111±3)MPa and(820±7)MPa,respectively,which is 8.8%and10.5%higher than those of reported.The results indicating the proposed multiscale computational approach for predicting grain growth and Lo F defects could allow simultaneous grain-structure control and defect mitigation during L-PBF.

Tailoring the microstructural characteristics and enhancing creep properties of as-cast Mg-5Bi-5Sn alloy through Mn addition

The creep properties, microstructural characteristics and creep mechanisms of as-cast Mg-5Bi-5Sn(BT55) alloy without and with Mn(BTM550) addition were investigated via creep at 423, 448, and 473 K as well as stresses of 30, 50 and 75 MPa. The results indicate that adding Mn can result in the formation of primary and the dynamic precipitated α-Mn phases. In addition, the morphology of the precipitated Mg_(3)Bi_(2) phase and the orientation relationship between Mg_(2)Sn precipitates and α-Mg can be effectively modified. Tailoring the microstructural characteristics is responsible for the improved creep performance of BTM550 alloy. The dominant creep mechanisms in BT55 and BTM550 alloys are dislocation cross-slip and climb, respectively. Furthermore, twinning and pyramidal slip play an assisting part in both alloys during creep process.

Iron/aluminum nanocomposites prepared by one-step reduction method and their effects on thermal decomposition of AP and AN

Aluminum(Al)powder is widely used in solid propellants.In particular,nano-Al has attracted extensive scholarly attention in the field of energetic materials due to its higher reactivity than micro-Al.However,the existence of aluminum oxide film on its surface reduces the heat release performance of the aluminum powder,which greatly limits its application.Hence,this paper used iron,a component of solid propellant,to coat micron-Al and nano-Al to improve the heat release efficiency and reactivity of Al powder.SEM,TEM,EDS,XRD,XPS,and BET were used to investigate the morphological structure and properties of pure Al and Fe/Al composite fuels of different sizes.The results show that Fe was uniformly coated on the surface of Al powder.There was no reaction between Fe and Al,and Fe/Al composite fuels had a larger specific surface area than pure Al,which could better improve the reactivity of pure Al.Besides,the catalytic effects of pure Al and Fe/Al composite fuels of different sizes on ammonium perchlorate and ammonium nitrate were explored.The results show that the catalysis of pure Al powder could be greatly improved by coating Fe on the surface of Al powder.Especially,the micron-Fe/Al composite fuel had a higher catalytic effect than the pure nano-Al powder.Hence,Fe/Al composite fuels are expected to be widely used in solid propellants.

Effects of stress loading mode on microstructures and properties of Mg-9Gd-2Nd-0.5Zr alloy treated by creep aging

Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stress loading method affects creep aging of Mg alloys is still unclear. In this paper, the microstructural evolution of precipitated phases and precipitation-free zones(PFZ) at grain boundaries with different stress loading modes(unstressed, unidirectional tensile stress, and cyclic stress) at 250 ℃ were investigated along with changes in mechanical properties. The results showed that the addition of stress during aging effectively promoted the precipitation of precipitated phases, while unaffecting grain size. Unidirectional tensile stress caused directional growth of β phase([1010]), as well as rotation of weave towards the basal plane texture, resulting in namely stress orientation effect. Solute atoms diffused in the direction of tensile stress while vacancies moved perpendicular to the direction of tensile stress, resulting in PFZ at grain boundaries(157.06 nm). By contrast, cyclic stresses led to the growth of β phase in three directions([1010], [1100] and [0110]). The solute atoms and vacancies were uniformly distributed in the Mg matrix instead of directional diffusion, effectively reducing the width of PFZ(112.39 nm) at the grain boundary. These features significantly improved the mechanical properties of alloy specimens after cyclic stress creep aging when compared to unidirectional stress creep aging, with yield strength(YS), ultimate tensile strength(UTS), and elongation(EL) enhanced from 171.6 MPa, 305.5 MPa, and 4.4%to 174.8 MPa, 326.3 MPa, and 6.9%, respectively.

Erratum to:Phase-field simulation of lack-of-fusion defect and grain growth during laser powder bed fusion of Inconel 718

The original online version of this article unfortunately contained a mistake.The reference[24]in the original online version is incorrect.The correct version is given below:Y.H.Cheng,Numerical Simulation and Experimental Research of Selective Laser Melting on Nickel Based Alloy Powder GH4169[Dissertation],North University of China,Taiyuan,2016.

Hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel

Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150℃ and the strain rate range was 0.01–5 s^(-1)on a Gleeble-3800 thermal simulator machine. The results showed that the flow stress increased with decreasing deformation temperature and increasing strain rate. According to the constitutive equation, the activation energy of hot deformation was 422.88 kJ·mol^(-1). The relationship between the critical stress and peak stress of the tested steel was established, and a dynamic recrystallization kinetic model was thus obtained. Based on this model, the effects of strain rate and deformation temperature on the volume fraction of dynamically recrystallized grains were explored. The microstructural examination and processing map results revealed that the tested steel exhibited a good hot workability at deformation temperatures of 1010–1100℃ and strain rate of 0.01 s^(-1).

Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers:Effect of sebacic acid as a third comonomer

Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry(DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10 T at a given temperature or relative crystallinity degree,which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope(POM) and X-ray diffraction(XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10 T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10 T, the crystallization rate was increased with the addition of the sebacic acid comonomer.

Effect of Sc and Zr on microstructures and mechanical properties of as-cast Al-Mg-Si-Mn alloys

Microstructures of as-cast Al-Mg-Si-Mn alloys with and without Sc and Zr were investigated by optical microscopy, scanning electronic microscopy(SEM) and energy dispersion spectrum analysis. Addition of 0.2%-0.4% Sc can refine the grain size and change the growth morphology from dendritic to fine equi-axial crystal. The higher the addition of Sc, the finer the as-cast grain size. The tensile strength is increased by more than 30% with 0.4% Sc. Moreover, an addition of 0.1%-0.2% Zr is able to refine grain size and change the growth morphology from dendritic to equi-axial grain too, but less effective. However, Zr is found to increase the ductility of the cast alloys, and the elongation is increased to 11.97% with 0.2% Zr.

Influence of Rare Earth Modification and Homogenization on the Microstructure and Mechanical Properties of Recycled Can 3004 Aluminum

The microscopic structure of waste can aluminum material was researched by adding A15TiB refining agent, La-Ce rare earth and mixed rare earth modifiers, and the microstructure and mechanical performance of the modified aluminum material were studied. The experimental results show that the optimal refiner addition amount is 1.1wt%; the material performance can be significantly improved when the content of La-Ce rare earth ranges to a certain degree, but the mixed rare earth barely affects the refinement effect of the aluminum. When being homogenized, the mixed rare earth plays more obvious role in refining the aluminum material than La-Ce rare earth. The optimal plan is modifying the aluminum material with 3wt% mixed rare earth and homogenizing with annealing temperature of 580℃, annealing time of 12 hours and heating rate of 5℃/min while refining the material with 1.1wt% A1-5Ti-IB.

New Technology of Multidirectional Loading Rotary Extrusion

To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement, a new multidirectional loading rotary extrusion forming technology is developed to match the linear motion with the rotary motion and actively increases the strong shear force. Its principle is that the radial force and rotating torque increase when the blank is axially extruded and loaded. Through the synergistic action of axial, radial, and rotating motions, the orderly fow of metal is controlled, and the cumulative severe plastic deformation (SPD) of an“uplift-trowel” micro-area is generated. Consequently, materials are uniformly strengthened and toughened. Simultaneously, through the continuous deformation of a punch “ellipse-circle,” a high reinforcement component is grown on the cylinder wall to achieve the high-quality formation of cylindrical parts or the inner-ring-reinforcement components. Additionally, the efective strain increases with rotation speed, and the maximum intensity on the basal plane decreases as the number of revolutions increase. The punch structure also afects the axial extrusion loading and equivalent plastic strain. Thus, the proposed technology enriches the plastic forming theory and widens the application feld of plastic forming. Furthermore, the formed large-scale high-performance inner-ring-stifened magnesium components have been successfully verifed in aerospace equipment, thereby solving the problems of integral forming and severe deformation strengthening and toughening. The developed technology has good prospects for mass production and application.

Microstructure evolution,texture and mechanical properties of a Mg-Gd-Y-Zn-Zr alloy fabricated by cyclic expansion extrusion with an asymmetrical extrusion cavity:The influence of passes and processing route

In the present work,two processing routes(A and B)with 3 CEE-AEC passes are performed on Mg-13 Gd-4 Y-2 Zn-0.4 Zr alloys,and the resultant microstructure evolution,texture analysis and mechanical properties are investigated systematically.The core difference between the two processing routes is the orientation between the expansion and extrusion steps,i.e.,they are parallel to each other for on route A and perpendicular to each other for route B.The results show that a remarkable grain refinement is achieved via both processing routes due to dynamic recrystallization(DRX).Fine equiaxed grains are observed in the samples processed with route B with a final size of 3.6±0.4μm compared to the grain size of 4.5±0.5μm with route A.With an increasing number of CEE-AEC passes,the overall texture intensity decreases,and the basal texture gradually changes to the mixed texture components.The shear deformation introduced by the asymmetrical extrusion cavity promotes a broad angular distribution of the basal planes on routes A and B,leading to an obvious increase in the Schmid factor for the activation of the basal a slip system.The tensile test at ambient temperature reveals that the comprehensive mechanical properties are improved,and the conventional mechanical anisotropy of as-received alloys is alleviated by successive CEE-AEC processing,which is mainly derived from the competitive balance relation between the grain refinement and texture modification.

Effect of heat treatment on mechanical properties and microstructure evolution of Mg-9.5Gd-4Y-2.2Zn-0.5Zr alloy

Regarding the as-cast Mg-9.5Gd-4Y-2.2Zn-0.5Zr alloy,the effect of heat treatment on its properties at room temperature(RT),as well as the mechanical properties and microstructure evolution of various peak-aging samples at different tensile temperatures were discussed in this article.The results indicated that the optimal heat treatment process of the alloy was:520℃×24 h+200℃×112 h.Under this condition,the yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)at RT were:238 MPa,327 MPa and 2.5%,respectively.As the tensile temperature increases,the strength increases firstly and then decreases,but the ductility increases monotonously.The microstructures evolution of 200℃ peak-aging(200PA)and 250℃ peak-aging(250PA)samples were different with the increasing tensile tenperature.When tensile test processed at 150℃,the denseβ’phase and rod-shaped basalγ’phase will be formed in the 200PA sample.However,at 300℃,theβ’phases disappeared.Theβ’and LPSO phases in the 250PA sample coarsened gradually as the tensile temperature increased,and 14H-LPSO phases were formed during tensile at 300℃.The 200PA sample reached the highest strength when tensile at 150℃,which was attributed to the hindrance of the basal dislocation and non-basal dislocation slip by the prismaticβ’phases and the newly formed basalγ’precipitates.

Low-cycle fatigue behaviour of Mg-9Gd-4Y-2Zn-0.5Zr alloys with different structures

The strain-controlled cyclic deformation behaviour of Mg-9Gd-4Y-2Zn-0.5Zr with different structures was investigated. Alloys were prepared by solution, extrusion and pre-ageing extrusion, and the microstructures before and after the fatigue tests were characterized.Experimental results indicated that the bimodal structure owned the better performance in fatigue test, which was attributed to the higher yield strength. For the equiaxed structure, cyclic hardening induced stress concentration until the failure. Stable cyclic deformation and persistent cyclic softening played an important role at the low and high strain amplitudes, respectively. This was attributed to the formation of fine grains relieving the stress concentration during cyclic loading. In addition, residual twins were observed in equiaxed structure to induce crack, and the bimodal structure effectively restrain it.

Effect of Cu addition on corrosion resistance and shape memory effect of Fe-14Mn-5Si-9Cr-5Ni alloy

The modification of Fe-14Mn-5Si-9Cr-5Ni shape memory alloys(SMAs) by copper addition was carried out, aiming at further enhancing its corrosion resistance. The results of electrochemical potentiodynamic measurement and immersion test show that copper can remarkably improve the corrosion resistance in Cl- solution. Otherwise, it is found that copper cannot markedly affect the mechanical properties nor the shape memory effect(SME). As for the effects of copper on Fe-Mn-Si based alloys, the austenite strengthening is one of the key factors to improve SME.

Phase-field-crystal simulation of nano-single crystal microcrack propagation under different orientation angles

The propagation mechanism of microcracks in nanocrystalline single crystal systems under uniaxial dynamic and static tension is investigated using the phase-field-crystal method.Both dynamic and static stretching results show that different orientation angles can induce the crack propagation mode,microscopic morphology,the free energy,crack area change,and causing fracture failure.Crack propagation mode depends on the dislocation activity near the crack tip.Brittle propagation of the crack occurs due to dislocation always at crack tip.Dislocation is emitted at the front end of the crack tip and plastic deformation occurs,which belongs to ductile propagation.The orientation angles of 9°and 14°are brittleductile mixed propagation,while the orientation angles of 19°and 30°are brittle propagation and no dislocation is formed under dynamic tension.The vacancy and vacancy connectivity phenomenon would appear when the orientation angle is14°under static tension,and the crack would be ductile propagation.While the orientation angle is 19°and 30°,the crack propagates in a certain direction,which is a kind of brittle propagation.This work has some practical significance in preventing material fracture failure and improving material performance.

Preparation of a halogen-free P/N/Si flame retardant monomer with reactive siloxy groups and its application in cotton fabrics

A novel halogen-free phosphorus–nitrogen–silicon flame retardant monomer with reactive siloxy groups,N-(diphenylphosphino)-1,1-diphenyl-N-(3-(triethoxysilyl)propyl) phosphinamine(DPTA) has been synthesized and was applied to the fire-resistant finishing of cotton fabrics. The molecular structure of DPTA has been well characterized by elemental analysis, FTIR,1H NMR, and ^(31)P NMR spectroscopies. The chemically-grafted cotton fabrics, which were treated with 25 wt% DPTA, were obtained and confirmed by attenuated total reflectance Fourier infrared spectroscopy(ATR-FTIR). The flame retardancy and thermal property of the treated samples were investigated by limited oxygen index(LOI), vertical flammability test(VFT), thermogravimetric analysis(TGA) and microscale combustion calorimeter(MCC). It is noted that in vertical flammability test, the treated samples extinguished immediately upon removing the ignition source, whereas the untreated one was completely burned out. Furthermore, TGA and MCC tests revealed that the treated samples produced a high char formation and a low heated release during combustion. The surface morphology of the untreated and treated samples and the char residues after LOI tests were observed by scanning electron microscopy(SEM). Therefore, all the results showed that the treated cotton fabrics with 25 wt% DPTA apparently improved the fireresistant and thermal performances.

Corrosion and mechanical properties of hot-extruded AZ31 magnesium alloys

AZ31 magnesium alloys were hot-extruded at 573 K and 623 K with extrusion ratio(λ) of 20,35 and 50.The corrosion and mechanical behavior of hot-extruded AZ31 were studied by galvanic tests and tensile tests.The microstructures of the studied AZ31 alloys were also investigated with optical microscope.The results show that,compared with the as-cast AZ31 alloy,the corrosion potentials of all hot-extruded AZ31 alloys are increased by 60 mV.Moreover,at the extrusion temperature of 623 K,the galvanic current of AZ31 alloy decreases with increasing extrusion and the galvanic corrosion resistance is increased by 10%with the extrusion ratio of 50.In addition,the tensile strength and elongation of the extruded alloys are significantly enhanced by about 20%and 140%,respectively.The improvement of corrosion resistance and obvious increasing of mechanical properties of AZ31 alloys by hot-extrusion are ascribed to grain refinement and microstructural modification together with the homogeneous distribution of intermetallic phases throughout the matrix.