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Shrinkage cavity, microporosity, blowhole and the likes are the typical void defects in ingot. Only through reasonable high temperature deformation and heat preservation process can the void defects be closed and welded to ensure the high quality of forgings. However, there are few researches on the welding behavior of voids, and the understanding of the void welding mechanism is still insufficient. In order to further study the welding behavior of void and explore the welding mechanism, the welding process of void and microstructure evolution around void under thermal mechanical coupling were studied by physical simulation. The results show that heating temperature, holding time, plastic deformation play an important role in void welding. The void welding degree increases with the increase of heating temperature, holding time and plastic deformation. Besides, there are three main welding mechanisms for void defects, including the volume of microvoids decreases due to vacancy diffusion, the void welding mechanism caused by the austenite-ferrite transformation at lower temperatures and the void welding mechanism caused by recrystallization and grain growth of austenite grains at higher temperatures.

During hot ring rolling and subsequent air-cooling processes, the as-cast metal alloy undergoes a complicated microstructural evolution. In this paper, the grain refinement of as-cast 42CrMo ring billet during hot ring rolling and air-cooling was conducted by FEM simulation and tests. Moreover, the grain refinement mechanism of as-cast 42CrMo was also studied by comparison of single-pass deformation and multi-pass deformation with short pass interval time, with the purpose of studying the influence of the deformation process on grain refinement supported by the results of FEM simulation. As a result, effective strain and average grain size of the ring show zonal distribution characteristics The effective strain on the inner and outer layers of the ring is large, contributing to fine and homogeneous grains. In contrast, the cumulated effective strain on the interlayer of the ring is small, resulting in inhomogeneous and mixed grains and large average grain size. Grain growth occurs during subsequent air-cooling. The microstructural distribution of the hot rolled ring was confirmed by a hot ring rolling test.

In this work, a frequently used coupling agent, 3-Aminopropyltriethoxysilane, was directly added and blended into polymer matrix to fabricate BaTiO3-P(VDF-CTFE) nanocomposites using different size of BaTiO3 nanoparticle fillers, for the purpose of studying the effect of ceramic-polymer interfacial area on dielectric properties of ceramic-polymer composite systems. It was experimentally found that the er, Eb and Udischarge of the nanocomposites with different size of the fillers was improved in varying degrees. Moreover, the nanocomposites using very fine fillers exhibit a maximally enhanced ratio of both dielectric constant and energy density. As a result of the improved compatibility and enhanced dielectric properties, a maximal discharge energy storage density of 3.8 J/cm3 was obtained from the nanocomposites using 5 vol% of the fillers in size of 50 nm. In summary, the simple method of direct addition of the coupling agent is proved to be suitable for fabrication of the ceramic-polymer nanocomposites using very fine fillers.

The hot-deformation behavior of the as-cast Mn18Cr18N high-nitrogen austenitic stainless steel, produced with the electroslag-remelting metallurgical technology, was studied using isothermal-compression tests in a temperature range of 1223–1473 K) and a strain-rate range of 0.001–1 s–1). The flow-stress curves of the Mn18Cr18N steel were obtained under different hot-deformation conditions. By establishing the hyperbolic sine-law Zener-Hollomon equation, the hot-deformation activation energy of the Mn18Cr18N steel was obtained. Based on the mechanism of dislocation evolution, a physically-based constitutive model was established. In addition, the expression of the dynamic-recovery coefficient of the model was modified. Compared with the model before the modification, the modified constitutive model could effectively improve the prediction accuracy of the flow stress for the as-cast Mn18Cr18N austenitic stainless steel.

In this work, mechanical properties and plastic deformation behaviors of columnar polycrystal are examined by compression tests using molecular dynamics simulation. The results show that anisotropic mechanical properties occur to the fcc FeCrNi samples with different inclined angles between the orientation of columnar grains and loading direction. The yield stress and flow stress of the α = 0° sample are the highest, while the values of α = 45° sample are the lowest among the tested samples. The reasons for these differences derive from the geometric constraint of grain boundaries (GBs) and the available slip systems of different grains. The GBs serve as obstacles where extended dislocations are incorporated rather than dislocation pile-ups at GBs. For the α = 0° sample, the GBs bending toward the radius direction coupled with less partial dislocation motion and twinning compensates the compression strain. The strain-assisted GBs migration along loading direction extensively takes place in α = 90° sample, whereas the numerous partial dislocation activity and GBs gliding occur in samples with the angle close to 45°. This results from the higher Schmid factors of slip systems of columnar grains within these samples and long mean free sliding path for GBs gliding. Besides, the influence of radius size is probed, exhibiting a constant Young’s modulus, but slightly different plastic deformation characteristics.

Cavity defects including a shrinkage cavity, air hole and porosity are typical defects of an ingot, which are difficult to avoid. These defects can disappear during deformation at a reasonably high temperature and heat-preservation process so as to ensure the quality of forgings. However, the current understanding of the mechanism of the void closure is insufficient, and the models that can accurately predict the evolution of a void are relatively rare. Based on the representative-volume-element model, a theoretical analysis and numerical simulation, the influence of the Lode parameter and stress triaxiality on the void closure is expounded. Besides, based on the above research, a new void-evolution model considering all kinds of macro-stress states is proposed. The model can predict the closure degree of voids in different positions and various macro-stress states during the plastic deformation of ingots. Comparing the new void-evolution model with other models, numerical simulations and physical-simulation results, the accuracy of the proposed void-evolution model is verified.

Li–S batteries (LSBs) are promising next-generation energy-storage devices due to their high theoretical capacity and cost effectiveness. However, the widespread use of LSBs is still impeded by the low conductivity of sulfur, the volume expansion of active materials, and the shuttle effect of lithium polysulfides (LiPSs) in practical conditions. In this work, a novel sulfur matrix integrating self-branched Nb2O5 nanoarrays and flexible carbon cloth (NBCC) is designed and prepared. The conformal S@NBCC composite provides surface-to-surface contact between sulfur and the catalytic mediator, thus exposing more active sites for trapping LiPSs. Meanwhile, the selected Nb2O5 nanoarrays with ultrafast Li+ motion capability can work as “electron-ion reservoirs” to further accelerate the conversion reaction of LiPSs. Moreover, the extra-free space among the branched nanoarrays can not only facilitate the infiltration of the liquid electrolyte, but also enhance its tolerance to volume expansion of sulfur during the lithiation process. Benefitting from these synergistic effects, the self-supported S@NBCC shows a high specific capacity of 1262.5 mA h g−1 at 0.1 C and maintains an impressive specific capacity of 759.6 mA h g−1 even after 300 cycles at 1 C, showing great potential in promoting the practical application of flexible LSBs.

The mechanical behavior of Mn18Cr18N steel along different loading paths was investigated at room temperature. In compression–tensile loading paths, the strain hardening behavior depends on subsequent tensile loading directions. When the subsequent loading axis coincides with the previous loading axis, the strain hardening path coincides with the strain hardening path in previous strain stage. When the subsequent loading axis changed, the subsequent strain hardening rate is remarkable greater than that in the previous strain hardening stage. The tensile ductility is different along different loading paths. In consecutive compression–tensile loading paths, the tensile ductility increased first and then decreased. Dislocation rearrangement caused good ductility during the tensile loading. In non-consecutive compression–tensile loading paths, the tensile ductility decreased gradually. Dislocation multiplication occurred rapidly during the subsequent tensile loading. Stress hardening is remarkable during compression–tensile consecutive cyclic loading when the strain amplitude is greater than 0.01. The maximum tensile stress can be reached up to 1549.6 MPa at 3 cycles with 0.15 strain amplitude, which is an increase of 395.4 MPa compared to the simple tensile loading. During complex loading paths, dislocation configurations and the substructures not only depend on the accumulated strains but also on the loading paths.

The experimental study of Bauschinger effect in Mn18Cr18N austenitic stainless steel was presented by compression-tensile cyclic loading tests with the prestrains ranging from 0.005 to 0.1, which was illustrated utilizing stress-strain curves and analysed by TEM images from aspects of microstructural mechanisms. Moreover, the Bauschinger effect and its associated roundness phenomenon in reverse flow curve with respect to different cycles and cyclic strain amplitudes were evaluated in a quantitative manner. The experimental results indicate that Bauschinger effect is apparent during the test. At smaller cyclic strain amplitude, intergranular backstress is the main source of Bauschinger effect. With further increasing of cycles, dislocation density increases and dislocation movement is hindered in the reverse deformation. Therefore, Bauschinger effect is weakened to some extent. At large cyclic strain amplitude, backstress originating from the dislocation pile-up at grain boundaries and the continuous formation of deformation twins dominate the Bauschinger effect. In addition, the backstress results in the roundness of reverse curve during cyclic loading. The larger value of Δep*, the more obvious the roundness of the reverse curve, and the more significant the Bauschinger effect.

In order to conduct numerical simulation of plasticity forming and confirm the processing parameters of heat deformation for as-cast CL70 steel, the hot deformation behaviors of as-cast CL70 steel were studied by isothermal compression tests which used a Gleeble-1500D thermal mechanical simulation tester for the deformation temperatures ranging from 1173 to 1523 K and the strain rates ranging from 0.001 to 1 s−1. Flow stress curves of the steel were obtained under high temperature. The flow stress constitutive models of the work hardening-dynamical recovery period and dynamical recrystallization period were established for as-cast CL70 steel. In work hardening-dynamic recovery period, the flow stress was predicted by employing the evolution rule of dislocation density in the constitutive model. In dynamic recrystallization period, the flow stress after the critical strain was predicted by employing the dynamic recrystallization kinetics in the constitutive model. To improve the prediction accuracy of the model, the dynamic recovery coefficient is modified in the traditional physically-based constitutive model. The results indicate that the proposed physically-based constitutive model has high accuracy in predicting the flow stress under hot deformation for as-cast CL70 steel.

This study is aimed to investigate the influence of substrate bias on mechanical properties and high temperature oxidation of sputtered TiN coating which is prepared on the surface of Zr-4 alloy. The microstructures of coatings were characterized by using scanning electron microscope (SEM) and X-ray diffractometer (XRD). The thicknesses of coatings were detected by examining the cross-sectional SEM image. The adhesion property was tested by using scratch testing. The residual stress was measured by using the XRD method. The tensile property was evaluated by standard tensile test. And the high temperature oxidation performance in air condition was also assessed. It was revealed that substrate bias has a significant influence on crystalline structure, surface micromorphology, thickness, adhesion strength, and residual stress. Nevertheless, tensile property and high temperature oxidation performance are affected by substrate bias indistinctively. From the cross-sectional SEM image, it can be found that thicker coating can be obtained in unit time with a lower substrate bias. The adhesion property does not vary monotonically with increasing negative substrate bias and the coating deposited with −100 V possesses highest critical load. The sputtered TiN coatings demonstrate a compressive residual stress and the magnitude of residual stress of coatings prepared with −200 V and −300 V is higher than that of coatings prepared with −50 V and −100 V. The tensile test reveals that there is no obvious difference between tensile properties of TiN-coated specimens prepared with different substrate bias and the Zr-4 alloy specimen. And the weight gains of high temperature oxidation of TiN-coated specimens with different substrate bias are almost the same and are lower than uncoated Zr-4 alloy specimen. The XRD and EDS results show that TiN coating is oxidized and cracked and the internal Zr-4 substrate is also oxidized when the specimen is exposed to high temperature circumstance for a long time.

The effect of an ultrasonic temperature and output power on microstructure and mechanical properties of 6063 aluminum alloy during solidification was investigated by optical microscopy, hardness test, tensile test, SEM. The results showed that compared with the grains in samples without UST, those of under UST are much finer. The grain size approaches to about 80 μm at 750 °C and 600 W and the grain size decreases continuously with falling of test temperature. The grain refinement is significantly affected by temperature than the output power of ultrasonic sound. After UST, the intermetallic phases volume fraction is about 6%, which is much smaller than that (about 11%) of without UST, and no dendrites exsist in the samples after UST. The fracture surface is more uniform without UST, and the reduction of cleavage plane and showing of a typical tearing characteristic demonstrates great improvement of this alloy's mechanical properties.

Continuously alternating loads and environmental temperature fluctuations can easily cause material aging and fatigue defects in some in-service infrastructures. In order to improve the load-bearing capacities of these infrastructures and prevent unexpected accidents, a flexible continuous detection system that can evaluate the health of these structural systems is needed. The detection system should have the advantages of integrated miniaturization, low cost, high stability and sensitivity, suitability for engineering applications, etc. A full-optical strain sensor based on tunable laser demodulation is designed in this paper. It uses a home-made control mainboard to monitor a 2425-T3 aluminum alloy during tensile and fatigue tests. The tensile test results indicate that the FBG sensor response correlates well with the strain measured using a strain gauge. Therefore, the load and strain can be both monitored via the FBG sensor response. The fatigue test results demonstrate that the FBG sensor presented is superior to the strain gauge and has better sensitivity and stability for vibration monitoring in complex environments. In this letter, we make full use of the FBG’s advantages including its small size and light weight to implement an integrated, miniaturized FBG sensor design with significant structural health monitoring applications.

A short route manufacturing process of retaining rings was put forward, which was composed of hollow ingots manufacturing by Electro-Slag Re-melting (ESR), hot ring rolling and cold expanding strengthening. And microstructure mechanisms, deformation characteristics, and process parameters during both of hot ring rolling and cold hydraulic expanding strengthening were investigated. The results show that the multi-pass flow stresses decreased with increase of interval time. During multi-pass compression, grain refined at lower temperature of 1050 °C by static recrystallization, then grain refined at higher temperature of 1150 °C by both of dynamic and static recrystallization. Based on the influence of the contact arc length ratio on strain penetration in the wall deformation zone, the driving roller radius of 500 mm and the pressure roller radius of 130 mm were determined for the ring rolling process ofφ712 mm/308 mm × 902 mm thick-wall hollow ingot. The optimum rotate velocity of the driving roller should be 0.8 rad/s. And the feeding velocity of the pressure roller should to be 1 mm/s for matching. During cold deformation, planar slip and twinning predominated at small and large deformation, respectively, to increase strength. For the hydraulic expanding process of ϕ937/672 × 1034 mm hollow forging, the optimum matching of 60° punch angle and 5 mm contact seal height can be adopted for obtaining well-shaped strengthening forgings.

The compact casting-rolling technique is an advanced method to produce seamless ring parts. The technique has been paid much attention in recent years. To find out the textual evolution rule of materials in this compact process, hot ring rolling of 42CrMo casting blank was conducted at different mandrel feed rates. The macro-textures of the as-obtained products were studied by X-ray diffraction, and micro-textural associated grain orientations were examined by electron backscattered diffraction techniques. The dominant textures in hot-rolled rings were similar, with γ-fibre consisted of {111} and {111} orientations as the most intense components. The α-fibre and e-fibre textures in the entire thickness of hot-rolled rings did not show significant change as feed rate increased. Moreover, shear textures, including Copper-type {112} and Goss {110} components were presented in different regions of hot-rolled rings. The grain refinement was found closely related to grain orientation and micro-texture evolution in the entire thickness. The inhomogeneous distribution of grain size in the hot-rolled ring at a higher feed rate resulted in poor plasticity and toughness, which was caused by inhomogeneous γ-fibre orientations, especially in the center layer of the ring. Overall, these findings look promising for future studies dealing with compact hot ring rolling processes.

Cr and Al coating were respectively deposited on Zr-4 alloy by magnetron sputtering and high temperature oxidation (HTO) tests were conducted in air environment at 1200 °C for 3 h for Cr-coated and Al-coated specimens. The morphology and phase composition of the specimens were detected by SEM, EDS and XRD. The adhesion properties were characterized by scratch test. The XRD results revealed that the two coatings were crystalline with preferred orientation. The results of scratch testing showed that critical load of Cr coating was higher than that of Al coating. After HTO test, the Cr-coated specimen was intact without cracking and spalling off, only the outermost layer of Cr coating was oxidized to a Cr2O3 layer of about 4 μm thick with a residual Cr layer of about 4 μm thick, and the internal zirconium alloy was not oxidized. For Al-coated specimen, besides the complete oxidation of the Al coating, there were also about 500 μm Zr-4 alloy oxidized on each side, and there were a lot of voids and cracks in the specimen. The EDS results indicated that a thickness of about 5 μm Cr-Zr diffusion layer developed at the interface between Cr coating and Zr-4 alloy for the Cr-coated Zr-4 specimen. While, for the Al-coated Zr-4 specimen, Al diffused into the specimen to a depth of about 100 μm, and Zr diffused almost to the outermost layer. Moreover, Sn in the Zr-4 alloy is concentrated at the interface between the residual Zr-4 alloy and ZrO2 layer. The obtained results manifested that Cr coating shows better oxidation resistance than Al coating.

The process of smelting, pouring, and solidification for steel determines the inevitable existence of all kinds of macroscopic and microscopic void defects in the ingot. These voids need to be eliminated by a proper plastic forming process. However, the mechanism of void closure is not well understood at present. In particular, the investigation on the evolution law of void closure under complex stress state is not deep enough. Based on the representative volume element model, numerical simulations and theoretical analysis, the effects of the spherical stress tensor and the deviatoric stress tensor on the evolution of void are expounded. It is found that the relative size of the three principal values of the deviatoric stress tensor determines the shape change of the void during plastic deformation. Besides, the change of the relative value of the principal values of the deviatoric stress tensor has little effect on the maximum compressive strain required for void closure. Moreover, the smaller the principal value of the spherical stress tensor is, the smaller the strain required for void closure is.

Hot deformation behavior of as-cast antibacterial austenitic stainless steel containing 3.60% copper was investigated in a temperature range of 900-1150 °C and strain rate range of 0.01-20 s−1. At strain rates higher than 1 s −1, the flow stress curves were corrected considering adiabatic heating. Kinetic analysis indicated that the hot deformation activation energy of steel was 376.02 kJ mol−1. The microstructural evolution under different temperatures was observed by optical microscopy. The nucleation sites for recrystallization and different orientations and twin ratios under different strain rates were analyzed by electron backscatter diffraction. The results showed that hot deformation was dominated by continuous dynamic recrystallization in the high-temperature and high-strain-rate region (1050-1150 °C, 1-20 s−1). On increasing the temperature and strain rate, the degree of recrystallization and twinning increased simultaneously. These phenomena promoted one another. Thus, the volume fraction of the recrystallized and twinned grains increased with the addition of Cu.

The aging precipitation behavior in Mn18Cr18N austenitic stainless steel was investigated at temperatures from 600 °C to 900 °C. During isothermal aging treatment, the primary precipitate was Cr2N with a = 0.478 nm and c = 0.444 nm, and it preferentially nucleates along initial grain boundaries and gradually grows towards the interior of grains in discontinuous cellular way. Meanwhile, a small amount of granular face-centred cubic M23C6 with a = 1.066 nm also were observed, which mainly form along grain boundaries. The effect of these precipitates on mechanical properties of the alloy was studied. It was found that precipitates result in degeneration of the matrix hardness. Meanwhile, the SEM morphologies of aged tensile sample show that the brittle fracture predominates during deformation, i.e. the fracture mode transforms from intergranular fracture to transgranular fracture with the increasing of aging time. Compared with the solution-treated sample, the strength of the aged tensile samples slightly decreases and plasticity remarkably deteriorates.

Hot deformation behavior and microstructure evolution of as-cast Mn18Cr18N austenitic stainless steel were investigated by isothermal compression experiments. The results indicate that the microstructure evolution of the as-cast Mn18Cr18N steel is sensitive to strain rates. Discontinuous dynamic recrystallization, characterized by nucleation and growth controlled by grain boundary migration, occurs at lower strain rates. However, higher strain rates result in higher adiabatic temperature rise, which could be contributed to dynamic recrystallization (DRX) nucleation and growth by acceleration boundary migration. In addition, at higher strain rates, a large number of deformation microbands in the interior of coarse columnar grains were observed, which would provide potential nucleation sites for DRX. Meanwhile, a great number of Σ3 twins were observed, which reveals that twinning accelerates the separation of subgrains from bulging grain boundaries, and the iterative processing among Σ3 twins and its variants promotes the transformation from specific CSL grain boundaries to random high-angle boundaries.

The compression and tensile consecutive deformation behavior and microstructure evolution of Mn18Cr18N steel were investigated by cyclic loading tests at room temperature and strain amplitude from 0.005 to 0.15. The results indicated that the cyclic loading stress-strain curves of the steel show plastic deformation characterized by almost the same working hardening rates without yield plateaus at various strain amplitudes. At the lower strain amplitudes from 0.005 to 0.01, the stress amplitudes and subsequent yield surface radius decreased with cycles, which suggest that stress softening occurs during cyclic loading. At the strain amplitudes from 0.02 to 0.15, the stress amplitudes and subsequent yield surface radius increased with cycles, which imply that stress hardening occurs during cyclic loading. With the increasing of strain amplitudes, the cyclic hardening coefficients monotonically increased, while the cyclic softening coefficients rapidly decreased. The maximum flow stress increased up to 1549.6 MPa after three cycles at the strain amplitude of 0.15, which increased by 395.4 MPa compared to the maximum uniaxial tensile flow stress. It was also demonstrated that the cyclic loading stress-strain behaviors (cyclic softening and hardening) depend on internal stress component rather than effective stress component. TEM observation shows that planar slip with parallel substructures along one direction at high number cycles evolved from various dislocation configurations at low number cycles occurs at the lower strain amplitude of 0.005; double planar slip with grid substructures along two directions at high number cycles evolved from parallel substructures along one direction at low number cycles occurs at the higher strain amplitude of 0.04. Internal stress could be released by dislocation rearrangement and activation of cross slips during cyclic loading process, which induce stress softening at lower strain amplitudes; while slipping and twining alone two intersectional directions caused stress hardening at higher strain amplitudes.

Hot deformation behavior of as-cast Mn18Cr18N austenitic stainless steel was studied in the temperature range of 950-1200 °C and strain rate range of 0.001-1 s-1 using isothermal hot compression tests. The true stress-strain curves of the steel were characterized by hardening and subsequent softening and varied with temperatures and strain rates. The hot deformation activation energy of the steel was calculated to be 657.4 kJ/mol, which was higher than that of the corresponding wrought steel due to its as-cast coarse columnar grains and heterogeneous structure. Hot processing maps were developed at different plastic strains, which exhibited two domains with peak power dissipation efficiencies at 1150 °C/0.001 s-1 and 1200 °C/1 s-1, respectively. The corresponding microstructures were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). It has been confirmed that dynamic recrystallization (DRX) controlled by dislocation slipping and climbing mechanism occurs in the temperature and strain rate range of 1050-1200 °C and 0.001-0.01 s-1; And DRX controlled by twinning mechanism occurs in the temperature and strain rate range of 1100-1200 °C, 0.1-1 s-1. These two DRX domains can serve as the hot working windows of the as-cast steel at lower strain rates and at higher strain rates, respectively. The processing maps at different strains also exhibit that the instability region decreases with increasing strain. The corresponding microstructures and the less tensile ductility in the instability region imply that the flow instability is attributed to flow localization accelerated by a few layers of very fine recrystallized grains along the original grain boundaries.

Hot deformation behavior and microstructure evolution of as-cast Mn18Cr18N austenitic stainless steel were studied by uniaxial compression experiments at temperatures from 1123 K to 1473 K under strain rates of 0.001–1 s−1 up to the true strain of 0.69. The true stress-strain curves, characterized by hardening and subsequent softening, varied with temperatures and strain rates. By multiple linear regressions of the flow stress-strain data, the hyperbolic sine constitutive equation for the steel was developed and the hot deformation activation energy is calculated to be 672 KJ mol−1, which implies that the recrystallization is sluggish during hot deformation. Furthermore, two dynamic recrystallization mechanisms, dislocation and twinning, were demonstrated. At higher temperatures and lower strain rates, the dynamic recrystallization was controlled by dislocation slip and climbing. The fully recrystallized grains, composed of sub-grains and various dislocation configurations, can be obtained at 1473 K and 0.001 s−1 up to the true strain of 0.69. However, the dynamic recrystallization was controlled by twinning at higher strain rates and lower temperatures. Most of recrystallized grains are composed of twins, micro-twins and dislocation cells in twins. It suggests that twinning plays an important role during nucleation and progress of DXR by inducing separation of bulged grain boundaries and accelerating the expansion of migratory boundaries. The uniformly refined recrystallized grains with a large number of Σ3 twins were obtained at 1373 K and 1 s−1 up to the true strain of 0.69.

In this work, dynamic recrystallization (DRX) behavior of 316LN austenitic stainless steel was studied by hot compression experiments at temperature range of 900–1200°C and strain rate range of 0. 005–0.5 s−1. The Arrhenius hyperbolic sine function was given to fit well with the hot deformation flow behavior of 316LN steel and the average activation energy (Q) was obtained. The variation of DRX fraction and average grain size was studied and modeled. Microstructural evolution of 316LN steel during hot deformation in condition of 1,100°C and 0.05 s−1 was studied by EBSD analysis. It was found that twining plays a significant role in nucleation and growth of DRX during hot deformation. The nucleation of DRX in 316LN steel was characterized by bulging of serrated grain boundaries. Twining took place near the serrated grain boundary in large amount, accelerating the separation of bulging from deformed parent grains to form DRX nucleus. At the steady state strain, uniformly refined DRX grains almost took charge of the microstructure of 316LN steel.

Although various inorganic particles have been confirmed as effective trappers to restrict the shuttle effect of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSB), the further reduction of LiPSs is impeded due to their low conductivity. This process results in sluggish redox kinetics at the interface of cathode/electrolyte and escaped LiPSs to electrolytes during long-term cycling. Herein, by advantageous functional integration of immobilization and conversion capability for LiPSs, a 3D aerogel with the composition of Co@CoO@N-doped carbon@graphene (Co@CoO@N-C/rGO) is designed and prepared. The dual-shells of N-C and polar CoO enable the strong chemical adsorption towards LiPSs through pyridinic – N-Li-bond and Co···S coordination, respectively. And the conductive Co core acts as a “scissor”, which catalyzes the transformation of adsorbed LiPSs into low-order ones, thus accelerating the kinetics of the liquid–solid nucleation and growth of Li2S. Moreover, the matrix of rGO serves as electrical networks, significantly promoting the transfer of electrons to the redox-active sites. Based on these synergetic effects, the LSB using Co@CoO@N-C/rGO modified separators exhibits outstanding electrochemical performance. For example, even at a rate of 1C, the cell still delivers a stable capacity of 555.4 mAh g−1 after 500 cycles for a pure sulfur electrode. Moreover, the relevant kinetic mechanisms including in situ Raman test are expounded in detail.

Titanium alloys are often used in aircraft manufacturing. Titanium sheet exhibits low formability and high springback at room temperature, and this causes significant challenges with conventional forming methods. In this study, the phenomena and mechanisms of the formability of TB5 titanium alloys in rubber forming were investigated. It was found that rubber forming was effective for TB5 titanium sheets. Wrinkling in rubber forming was controlled by the side blankholder. The effects of the design parameters of the side blankholder on wrinkling were studied. A typical part was used to investigate the rubber cold forming of TB5. The largest height of the wrinkle became smaller with the increase of the forming pressure, while the hardness of rubber had little effect on the wrinkling. In order to eliminate the wrinkles completely, a wedge was introduced to increase the forming pressure on the shrink flange. Using the wedge, the forming pressure was increased a lot, and the wrinkles were flattened. Springback was controlled by die compensation. Aging treatment was used to increase the strength and part accuracy. After the aging treatment, the internal stress in the cold forming was released. The springback of the flange was corrected.

This paper aims to explore the effects of C addition on the formed microstructure in undercooled Cu–Fe alloys. C addition changed the microstructure morphology and phase composition of the undercooled Cu–Fe alloys due to striking entropy changes. The composition analysis indicated that C was dissolved in both Fe-rich and Cu-rich phases, but the C content in the Cu matrix was lower than that in the Fe-rich phase. The addition of C element significantly improved the miscibility between the separated Fe-rich phase and the Cu-rich phase, thus resulting in the Fe-rich particles from the liquid phase separation disappearing in Cu–10Fe–2C alloy microstructure.

Paper–plastic packaging materials have become important materials in the printing industry. Water-based paper–plastic laminating adhesive is a new type of adhesive that has been widely applied in the modern packaging and printing industry. The adhesive used for medical packaging materials asked for higher performance, such as stability, peel strength, and aging resistance, so there is a large necessity in developing an environment-friendly paper–plastic laminating adhesive with excellent performance. Wax emulsion, natural latex and waterborne polyurethane emulsion are mixed in the experiment, while epoxy resin emulsion was added to blending modification. The paper discusses the influence of the dosage of epoxy resin emulsion, wax emulsion, and waterborne polyurethane emulsion for T-peel strength and paper breakage rate; also, the storage stability of the emulsion, partical size, and partical size distribution and differential scanning calorimeter are tested to determine the best prescription of the paper–plastic adhesive. Copyright © 2015 John Wiley & Sons, Ltd.

Bulk MgB 2 samples containing x wt.% urea ( x = 0, 1.5, 2, 2.5, and 6) have been prepared by conventional solid state sintering at 800 °C. The effects of urea on the microstructure, in particular the MgO existence form, and the superconducting properties were investigated. With the help of the decomposition product of urea, the supposed large MgO agglomeration partially dissolved to be nano-sized particles (∼10 nm), which served as effective pinning centers rather than current barrier, and increased the upper critical field. As a result, the critical current density of the 2 wt.% urea-doped MgB 2 sample was enhanced (4 × 10 3 A cm −2 , 20 K and 3 T) in contrast with the un-doped sample when the field is larger than 2.5 T. However, the decomposition product inevitably dissolved the MgB 2 particles as the side effect, deteriorating the grain connectivity and therefore leading to a yet acceptable decrease of low-field critical current density. Taken all these into accounts, urea doping is still a more straightforward way to reduce MgO than pre-treating the powder with extra acid.

Thin aluminium sheets have great usage in aircraft manufacturing due to their light weight and high strength. Wrinkling is one of the major defects in the rubber forming of aluminium sheets and may be an obstacle to assembling the parts. In this study, wrinkling was analyzed by shrink flanging in rubber forming process with orthogonal experimental design. Four effect factors (die radius, the flange length, die fillet radius and forming pressure) were analyzed. Three alloy materials (2024-O, 7075-O, 2024-T3) were used as material. The area of wrinkles was introduced to analyze the difference of the effect factors. It was found that different factors had large effect on the wrinkling. The extent of wrinkling of different materials agrees well with their strengths. The best range of the forming pressure is under 300 bar for 2024-O and 7075-O. Wrinkling can be predict using numerical simulation. Three steps forming is a good method to control wrinkling of shrink flange in rubber forming process.

Rubber forming is very widely used in aircraft manufacturing. Springback of rubber forming process is an important and decisive parameter in obtaining the desired geometry of the part and design of the corresponding tooling. In this research, the rubber forming of aluminium sheet was conducted. To investigate the springback, the straight flanging was employed in die design. The deformation process was studied by preparing the sheets with different thicknesses and different die radii. The influence of process parameters (time and pressure) on the rubber forming process was studied. Based on the analysis of experimental results, it was found that springback of straight angle decreased with the increase of blank thickness t, whilst increased with the increase of the die radius r. The springback can be eliminated with the bending ratio r/t < 2. The increase of forming pressure and time of rubber forming had little effect on the springback when the blank coincided with the die face. Springback of flanging in rubber forming process was smaller than that of stamping. In the jogged flanging, a better shape was formed by using the polyurethane.

As a candidate technology for accident tolerant fuel (ATF), surface modified Zr cladding has captured the interest of an army of nuclear workers in the past few years. In this paper, three coatings (TiN, Cr, and TiN/Cr) were deposited on Zr-4 by direct current magnetron sputtering. The microstructural properties of the three coatings were detected by using scanning electron microscope (SEM) and X-ray diffraction (XRD). The thickness of coating was determined by examining the cross sectional SEM image. The adhesion properties of was characterized by using scratch testing. The thermal shock resistance (TSR) tests were carried out in three temperature variations, that is, △T = 800 °C, 1000 °C, and 1200 °C, respectively. After the TSR test, the surface morphology of the tested specimens was observed, XRD, SEM and energy dispersive spectrometer (EDS) were used to examine the microstructural properties of the tested specimens, and scratch testing was executed to determine the adhesion properties. The results show that TiN coating was partially peeled off and the inner zirconium alloy was oxidized. And the thickness of the generated ZrO2 layer is about 50 μm. The specimens coated with single Cr coating remained intact. The cross-sectional analysis result show that only about 30% of Cr coating is oxidized, and the residual Cr coating and inner zirconium alloy are not oxidized. It is mainly due to the dense and uniform structure of Cr2O3 formed by the oxidation of the outermost layer of Cr coating, which prevents the further penetration of oxygen into the interior and plays a very prominent protective role. For the bilayer TiN/Cr-coated specimens, the coefficient of thermal expansion (CTE) of intermediate TiN layer is different from that of zirconium alloy substrate. After TSR test, cracks and a large number of pores appear, and there are obvious gaps between the bulk oxidation products, which leads to poor protection of the internal materials. It indicates that the zirconium alloy coated with a single Cr coating has excellent TSR property.

Wrinkling is one of the main failure modes in sheet metal forming process and may lead to assembly problems of the parts. Control of wrinkling is difficult due to the complex deformation behavior of the sheet metal. A finite element model for side blankholder method to control wrinkling was established and used for the simulation. Trials and simulations were conducted to analyze the parameters of wrinkling characteristics. Results show that with the increase in the angle of the side blankholder, the resistance force of the side blankholder decreases. The blank length on the side blankholder should be small enough. The fillet radius of the side blankholder should be large enough to reduce the deformation. The bottom gap between the die and the side blankholder cannot be too large because the support of the blank will decrease in the forming process. In order to verify the simulation results, three blank lengths (20, 15, and 5 mm) over the side blankholder were used in the experiment. The results of the comparison tests testify the reliability of the simulation. The optimal parameter of the blank length is 5 mm. A new clamp method was designed for wrinkling control to overcome the shortcomings of the side blankholder method. The precision of the part met the requirement using soft rubber and two layers of rubber plates.

The tensile tests of Mn18Cr18 N austenitic stainless steel plates with rolled reductions of 10%–40% were investigated, in which the tensile loading direction is perpendicular to the direction of rolled loading. The variation of tensile properties and microstructures of rolled Mn18Cr18 N plates with different reductions were analyzed. The results show that the tensile stresses increased with increasing of rolled reductions. And the plasticity indices decreased with the increasing of rolled reductions. The maximum tensile stress value of 1394 MPa before necking was obtained at the 30% rolled reduction, the corresponding yield stress is 1092.0 MPa, and the corresponding elongation is 37.9%. The tensile microstructures observed by OM and TEM indicated that grain refinement and grain orientation occurred. Deformation microstructures characterized by planar slips, twin-like bands and twins with increasing of rolled reductions, which resulted in the increasing of tensile stresses and the decreasing of plasticity indices of the rolled plates with increasing of rolled reduction. It also caused the tensile fracture morphologies from ductile fracture with dimples to brittle fracture with cleavage steps with increasing of rolled reductions. The transition rolled reduction from ductile fracture to brittle fracture is 30%, which is independent on loading path.

Thermal behavior of three pure sulfates (CaSO4, K2SO4 and Na2SO4) as well as solid-phase reactions between each sulfate and cement raw materials (CaO-SiO2-Al2O3-Fe2O3, CSAF) at high temperature were investigated experimentally. As the results, K2SO4 is much more thermally stable and less reactive than CaSO4 and Na2SO4 in the CSAF system, moreover, CaSO4 and Na2SO4 can facilitate the formation of 2CaO·SiO2 (C2S) and reduce eutectic temperature of cement raw materials by 100 °C. CaSO4 can react with Al2O3 and CaO to form the mineral 3CaO·3Al2O3·CaSO4 ( C 4 A 3 S - ) at 1250 °C, while the formation temperature is decreased to 1150 °C in the CSAF-Na2SO4 system. For CSAF-K2SO4 system, the decomposition rate is very slow at low temperature, and K2SO4 can react with Al2O3 to form K3AlO3 at high temperature. For CSAF-Na2SO4 system, Na2SO4 can be easily melted to liquid phase, and react with CaO·SiO2 (CS) and C2S to generate Na2O·3CaO·2SiO2 (NC3S2) in the CSAF system, then inhibit the formation of 3CaO·SiO2 (C3S) in the clinker.

Hydrophobic coatings for practical applications demand good durability of hydrophobicity and excellent adhesion. Therefore, the preparation of crosslinked crystalline polymers with perfluoroalkyl side-chains and long alkyl side-chains were proposed. In this paper, the influence of the crosslinking on the crystallization of fluorinated acrylate copolymers was investigated through experimental and molecular dynamic simulation results. According to the FT-IR spectroscopy, XRD data and DSC curves, P(SA-co-HEMA-co-FOEMA) was amorphous, while P(SA-co-FOEMA) and the cured resin formed crystalline polymers with hexagonal packing of alkyl side-chains, and the degree of crystallinity in the cured resin is larger than that in P(SA-co-FOEMA). These phenomenons were further interpreted through the snapshots of the equilibrated systems, the radial distribution function, and the concentration profiles. Intramolecular hydrogen bonds and arrangement of main-chains, corresponding to the embedding of N3300, were considered to contribute to these phenomenons. These findings could be expanded to other comb-shape crystalline polymers for preparing functional surfaces and smart materials.

Two types of magnetostrictive resonators – magnetostrictive microcantilever (MSMC) and magnetostrictive particle (MSP) – have been introduced as sensor platforms. Their principles and advantages as sensor platforms are discussed along with the materials selection. A detailed and complete comparison between the MSMC and MSP is given. It is concluded that for the resonators with the same size, an MSP exhibits a higher sensitivity and has a much higher resonant frequency. For the resonators with the same resonant frequency, MSMCs exhibit a much higher sensitivity and have a much smaller size than MSPs. Using antibody as the sensing element, MSP biosensors for in situ detection of Escherichia coli and Listeria monocytogenes are developed and characterized. These biosensors exhibit a high performance. For example, the MSP-antibody biosensors of 1 mm × 0.3 mm × 15 μm exhibit a detection limit less than 100 cfu/ml for in situ detection of bacterial cell in water. A new type actuator is introduced using MSPs. The MSP actuator is operated using AC magnetic field with a frequency close to, but different than, its resonant frequency. The MSP actuator exhibits an unlimited displacement, and its moving direction is controlled by the operating frequency used.

The microstructure evolution of TC11 alloy with lamellar structures deformed at temperatures of 980–850°C and strain rates of 0.001, 0.01 and 0.1 s−1, and the static structure evolution and mechanism of the alloy annealed at different temperatures were investigated. The results show that dynamic recrystallization process at higher reduction, higher temperature and lower strain rate is almost complete, and the globularized fraction of the annealed microstructure mainly depends on the dynamic recrystallization during deformation. But the dynamic recrystallization process at lower reduction, lower temperature and higher strain rate is restrained, and the globularized fraction of the annealed structure depends on both of the deformation state and the static recrystallization process during annealing. α-grain size mainly depends on annealing temperature and holding time mainly. EBSD tests of dynamic and static globularized microstructures show that the mechanism of static globularization during annealing involves the static recrystallization of β-phase and the static recovery of α-phase, and subsequent globularization and coarsening.

A white-emitting phosphor Sr2SiO4: Pr3+ was synthesized through a solid-state reaction, and characterized by XRD, scanning electron microscopy (SEM), fluorescence spectrophotometer and thermo luminescence (TL) meter. Its emission spectra is composed of bluish purple (peaking at 390 nm), green (peaking at 535 nm) and red (peaking at 604 nm) light emission. They originate from the transitions of 4f → 5d, 3P0 → 3H5 and 1D2 → 3H4 of Pr3+. The afterglow emission spectrum is similar to the emission spectra. And the afterglow can last over 40 min in darkness. The TL curve shows that there is only one thermo luminescence band peak at about 376.480 K, which is responsible for the long-lasting emission.

It is the basis for the new casting-rolling compound forming technology to investigate the rules of rolling deformation and microstructure evolution of casting ring blank. The initial rolling temperature of casting ring blank is one of the key factors influencing deformation and dynamic recrystallization behavior. In this paper, dynamic recrystallization models of as-cast 42CrMo steel were derived from thermo-simulation experimental results. Then, under DEFORM-3D software environment, deformation and dynamic recrystallization of 42CrMo casting ring blank were simulated at different initial rolling temperature by coupled thermo-mechanical finite element method. According to the simulation results, the effects of initial rolling temperature on strain fields distribution and dynamic recrystallization of 42CrMo casting ring blank were discussed. The results show that: (1) increased initial rolling temperature makes plastic deformation expand from ring’s outer and inner-layer to middle and distribute ever more evenly; (2) increased initial rolling temperature can lead to increased dynamic recrystallization fraction, but grain size of ring’s inner and outer-layer becomes smaller and smaller, while that of mid-layer coarser and coarser.Copyright © 2013 by ASME

Food borne illnesses from the ingestion of S. typhimurium have been of primary concern due to their common occurrence in food products of daily consumption. In this paper, micron size, magnetoelastic (ME) biosensors for the detection of S. typhimurium were fabricated and tested in liquid solutions containing known concentrations of S. typhimurium cells. The biosensors are comprised of a ME sensor platform and immobilized bio-molecular recognition element (E2 phage) that has been engineered to bind the S. typhimurium multi-valently. The micron size ME sensor platforms were manufactured using microelectronics fabrication techniques. Phage was engineered at Auburn University and immobilized onto all surfaces of the sensor. The ME biosensor oscillates with a characteristic resonance frequency when subjected to a time varying magnetic field. Binding between the phage and bacteria, adds mass to the sensor that causes a shift in the sensor's resonance frequency. Sensors with the dimension of 500x100x4 μm were exposed to S. typhimurium with increasing known concentrations ranging from 5 x10 1 to 5 x 10 7 cfu/ml. The ME biosensor exhibited high sensitivity and a detection limit better than 50 cfu/ml.

Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME) biosensors. The biosensor is composed of a ME resonator platform coated with filamentous E2 phage, engineered to bind with S. typhimurium . The ME biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. The sensors used in this study were 0.028 mm × 0.2 mm × 1 mm in size. In this study, the tomato surface was spiked with S. typhimurium suspensions with concentrations ranging from 5 × 10 1 to 5 × 10 8 CFU/ml and then allowed to dry in air. The detection was conducted by directly placing ME measurement biosensors and control sensors on the spiked surface for 30 min in a humid environment. The control sensors were identical to the measurement biosensors, but without phage. Both measurement and control sensors were blocked with BSA to reduce non-specific binding. The resonance frequencies of both measurement and control sensors were measured prior to and after the placement of the sensors on the tomato. Shifts in the resonance frequency of the measurement biosensors were observed, while the control sensors showed negligible change. Scanning electron microscopy (SEM) was used to verify the specific binding of S. typhimurium to the biosensor. Results of multiple biosensor detection and corresponding analyzes showed statistically different responses between the measurement and control sensors for tomatoes spiked with S. typhimurium suspensions with concentrations of 5 × 10 2 CFU/ml and greater. This study demonstrates the direct detection of food-borne bacteria on fresh produce.

Magnetoelastic (ME) sensors provide a fast, sensitive method to detect bacteria with smaller sensors have higher mass sensitivity for detecting lower concentrations of bacteria. However, signals from smaller sensors are weaker and have more noise due to manufacturing defects. In this paper, we present a biosensor system for the detection of Salmonella typhimurium using multiple magnetoelastic sensors, each with the size of 2000 × 400 × 30 μm. The sensors are immobilized with E2 phage, which specifically binds with S. typhimurium. Unlike traditional methods, our system uses a step pulse to “shock” the sensor, causing it to vibrate at its natural resonance frequency and produce a signal in the pickup coil due to reverse magnetostriction. A Fast Fourier Transform (FFT) was used to determine the resonance frequency. As the biosensor captures S. typhimurium cells, its mass increases with a corresponding decrease of its resonance frequency.The detection system was composed of one coil with a reference sensor to monitor stability, and another coil with three measurement sensors separated in three tubes for simultaneous detection of bacteria. With multi-sensors the effect of a manufacturing defect is decreased and we get the benefit of averaging for more accurate and reliable results. Stability tests show that the variance of frequency detection is less than 122 ppm of its resonance frequency. SEM pictures of the sensor surface show a uniform binding of S. typhimurium cells. Cells were counted and the mass change calculated. The measured frequency change corresponds well to the theoretical change. The results show that the multiple phage based ME biosensors are able to simultaneously detect S. typhimurium and offer good sensitivity and reliability of detection.