Lattice Stress Research Articles

Homogeneous elasto-plastic deformation and improved strain compatibility between austenite and ferrite in a co-precipitation hardened medium Mn steel with enhanced hydrogen embrittlement resistance

A co-precipitation hardened medium-Mn steel with respective NiAl and Cu-rich particles in dual phases (austenite and ferrite) has been designed by using a quenching-partitioning-tempering (QPT) treatment. The influences of co-precipitates on the elasto-plastic transition and strain compatibility has been investigated based on the micro-mechanical behavior of constituent phases, the evolution of lattice strain and stress components. Compared to the Cu-Free steel, in which single NiAl precipitates form in ferrite, co-precipitation in the Cu-Added steel results in an improved strain compatibility between austenite (γ) and ferrite (α). The lattice strains of both γ and α phases show similar evolutions during the entire strain regime, and a homogeneous elasto-plastic deformation occurs together with a continuous yielding and weak transient of strain hardening rate. The improved strain compatibility leads to an alleviation of strain localization in the phase interfaces, so that the overall back stress increases slowly with the tensile strain increasing during the whole plastic deformation process, although the transformation-induced plasticity (TRIP) effect of the Cu-Added steel only occurs at low strains (<5%) due to the low mechanical stability of the retained austenite. In contrast, a non-continuous yielding of the constituent phases occurs in the Cu-Free steel leads to strong strain transfer across the α/γ interfaces due to a low deformation compatibility between austenite and ferrite. High internal stress in the phase interfaces results in easy damage-crack formation, but it can be accommodated by the TRIP effect which dominates in large strains, resulting in back stress decreasing and effective stress hardening during the subsequent deformation stage. However, the introduction of hydrogen can aggravate the dislocation accumulation and strain transfer between austenite and ferrite; thus, hydrogen-induced cracks (HICs) are prone to nucleate at the α/γ interfaces while the TRIP effect is not significant, leading to premature failure and significant elongation loss (85.4%) of the Cu-Free steel. Therefore, the improved strain compatibility of the Cu-Added steel contributes to a better resistance to hydrogen embrittlement, although both medium Mn steels possess similar tensile strength (1 GPa) and elongation (25%) values.

Structural and chemical network studies of thermal chemical vapour deposited ZnO nanostructured thin films

In this work, we have investigated the role of process temperature on microstructural, structural, vibrational and phonon behaviour of Zinc Oxide Nanostructured (ZnO-NS) thin films deposited via thermal chemical vapour deposition reactor (TCVD) on Si substrate. The various spectroscopic methods such as Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Raman Spectroscopy were used to evaluate its morphology, structural, vibrational and phononic behaviour. We have observed that the change in process temperature considerably modifies the inherent material properties of ZnO-NS thin films. The AFM result revealed that the density distribution of agglomerated ZnO-nanograins increases with increasing process temperature from 650° C to 750° C. XRD result revealed that the average crystallites size of ZnO-NS thin films was decreased from 22.35 to 12.47 nm with increasing process temperature. The lattice strain and stress in ZnO-NS thin films decrease with increasing process temperature. The FTIR spectra revealed the decreasing intensity of ZnO stretch with increasing process temperature indicates a change in defect distribution of nanostructure at the higher temperature. The Zn-O–H bond shows asymmetry towards the lower wavenumber region can be attributed to the presence of another chemical compound with similar bonding strength overlap with each other. The Raman spectrum confirmed that the FWHM of E1(TO), E2(high), A1(LO) and E1(LO) phonon were increased whereas FWHM of A1(TO) and SO phonon decreased with increasing process temperature. The phonon lifetime of various phonons was calculated using energy-time uncertainty relation and found that the phonon lifetime of E1(TO), E2(high), A1(LO) and E1(LO) phonon decreased with increasing process temperature.

Numerical estimation of lattice strain, bending and generation of misfit dislocations in CdHgTe heterostructures grown on GaAs substrate

Using our own computer program, we determined the spatial distribution of lattice strains in the HgCdTe heterostructure grown on a GaAs substrate. Lattice stress resulting from lattice mismatch between the substrate and the epitaxial layer and bending of the heterostructure is almost completely relaxed by misfit dislocations forming matrixes in the interfaces’ areas. The average distances between dislocation lines in individual interfaces were calculated based on the minimum energy, i.e. elastic energy condition resulting from the interaction of stress fields and deformations caused by lattice misfit, bending and the presence of dislocation plus electrical energy of dislocations.

Effects of microwave oxygen plasma treatments on microstructure and Ge-V photoluminescent properties of diamond particles**Project supported by the Key Project of the National Natural Science Foundation of China (Grant No. U1809210), the National Key Research and Development Program of China (Grant No. 2016YFE0133200), the Belt and Road Initiative International Cooperation Project from Key Research and Development Program of Zhejiang Province,

The microstructure and Ge-V photoluminescent properties of diamond particles treated by microwave oxygen plasma are investigated. The results show that in the first 5 min of microwave plasma treatment, graphite and disordered carbon on the surface of the particles are etched away, so that diamond with regular crystal plane, smaller lattice stress, and better crystal quality is exposed, producing a Ge-V photoluminescence (PL) intensity 4 times stronger and PL peak FWHM (full width at half maximum) value of 6.6 nm smaller than the as-deposited sample. It is observed that the cycles of ‘diamond is converted into graphite and disordered carbon, then the graphite and disordered carbon are etched’ can occur with the treatment time further increasing. During these cycles, the particle surface alternately appears smooth and rough, corresponding to the strengthening and weakening of Ge-V PL intensity, respectively, while the PL intensity is always stronger than that of the as-deposited sample. The results suggest that not only graphite but also disordered carbon weakens the Ge-V PL intensity. Our study provides a feasible way of enhancing the Ge-V PL properties and effectively controlling the surface morphology of diamond particle.

Interstitial doping enhances the strength-ductility synergy in a CoCrNi medium entropy alloy

An equiatomic CoCrNi medium entropy alloy (MEA) with face-centered cubic (FCC) structure exhibits excellent combination of strength and ductility. Here we employ interstitial doping to enhance its mechanical performance. Interstitial CoCrNi MEAs with two different carbon contents, i.e., 0.5 at. % and 1 at. %, as well as a carbon-free CoCrNi reference MEA have been studied. The results show that up to 1 at. % carbon can be fully dissolved into the homogenized plus water-quenched FCC solid solution structure. Subsequent annealing leads to precipitation of nano-sized M23C6 type carbides which provide dispersion strengthening and enhanced strain hardening. The best combination of ultimate tensile strength of 1180 MPa at an elongation above 60% was obtained in fine grained CoCrNi doped with 0.5 at. % of carbon. Carbon alloying is also shown to significantly increase the lattice friction stress. Dislocation glide and mechanical twinning act as main deformation mechanisms. Thus, the joint contribution of multiple deformation mechanisms in the carbon-doped MEAs leads to significantly enhanced strength-ductility combinations compared to the carbon-free reference alloy, demonstrating that interstitial alloying can enhance the mechanical properties of MEAs.

Gigahertz coherent longitudinal acoustic phonons in GaAs Single crystals with different orientations

We report an experimental study on the ultrafast dynamics of coherent longitudinal acoustic phonons (CLAPs) in GaAs single crystals with different orientations by using femtosecond pump–probe technique. Under an above-bandgap pumping at 400 nm, the CLAP wave is generated on the surface of a GaAs crystal with [100] orientation, and then it propagates into the crystal and is detected by the transient reflection of the probe beam at 800 nm. As the pumping intensity is increased, the amplitude and lifetime of generated CLAPs in GaAs crystals are increased and decreased respectively, while the phonons oscillation frequency remains a constant of 44.3±0.2 GHz. Furthermore, the CLAPs frequency is varied in GaAs crystals with different orientations which is determined by the elastic anisotropy. In addition, from the initially opposite oscillation phase of [100] and [111] oriented GaAs, tensile or compressive lattice stresses can be easily determined. Our results can facilitate the understanding of ultrafast phonon dynamics in GaAs single crystals.

Magnesium-rich nanoprecipitates in calcite: atomistic mechanisms responsible for toughening in Ophiocoma wendtii.

The brittlestar Ophiocoma wendtii is theorised to employ a technique already used in metallurgy in order to optimise the mechanical properties of calcitic microlenses within their skeletons. These microlenses contain arrays of Mg-rich nanoprecipitates, which are proposed to inhibit crack propagation through the compression of the local host lattice. Here, we employ classical molecular dynamics in order to study the effects of Mg-rich nanoprecipitates on lattice strain, stress distributions and crack propagation in calcite. Our quantitative results on lattice strain and stress induced on the host matrix are compatible with empirical estimates. Simulations of crack propagation demonstrate that the inclusion of a Mg-rich region results in an increase in stress required to fracture the crystal, as well as higher residual stress in the fractured crystal. This is the result of an inhomogeneous stress distribution causing a more disordered fracture, as well as deflections of the crack away from the lowest energy (10.4) surface. The results agree with the proposal that the compression of the host lattice inhibits propagation, and offer insight into other mechanisms through which the nanoprecipitates affect crack propagation.

Модификация структуры градиентных покрытий Ti-Al-Si-Cu-N при механических испытаниях

The research of structural state at the indentation and scratch regions of the gradient coatings Ti-Al-Si-Cu-N was carried out with the use of dark field electron microscopy analysis method of the crystal lattice bending. It was found out that the strength properties of the substrate, which determine the degree of plastic relaxation of the applied load are significant for modifying the coating structure. The increase of the crystal lattice bending relative to undeformed state, the heterogeneity and anisotropy of its value relative to the point and axis of the load are found for the material under the indenter apex. The formation of the localized bands is shown, in which the increase of crystal sizes, decrease in the bending of the crystal lattice and residual local stresses were observed.

Crystal growth and optical properties of ammonium dihydrogen phosphate (ADP) crystals doped with Fe(II) and Fe(III): Oxidation number effects

Single crystals of Fe(II) and Fe(III) (1 mol %) doped ammonium dihydrogen phosphate crystals were obtained by slow evaporation solution growth technique (SEST). Single crystal X-ray diffraction studies of doped samples shows slight structural changes. The obtained crystals was further characterized by FT-IR, SEM, UV-DRS. The band gap energies of the crystals were estimated by the application of Kubelka-Munk algorithm. Second harmonic generation (SHG) efficiency of Fe(II) and Fe(III) crystals let out that Fe(II) doping in ADP has better nonlinear optical (NLO) property than Fe(III) due to lattice stress.

Stress localisation in lamellar cementite and ferrite during elastoplastic deformation of pearlitic steel studied using diffraction and modelling

Synchrotron X-ray diffraction was applied to study the evolution of lattice strain and stresses in both phases of pearlitic steel during a tensile test. The advantage of the methodology used in this work is the possibility of experimental study of stress localisation, which is directly determined from measurements and can be used to study the process of strain strengthening of lamellar pearlite. It was found that in the elastic range of deformation, both cementite and ferrite are loaded similarly due to the nearly equal elastic properties of both phases, while plastic deformation leads to significant load transfer from ferrite to cementite. Due to the complexity of the lamellar microstructure of the material, the classical elastic-plastic self-consistent model does not correctly predict the partitioning of the stresses between phases during plastic deformation. Therefore, the grain-matrix interaction given by the self-consistent model was modified and successfully applied to simulate the interaction between phases.The synchrotron experiment allowed us to determine the critical resolved shear stresses of ferrite phase in the pearlitic steel subjected to different thermal treatments. The role of cementite in material strengthening was evaluated on the basis of the evolution of von Mises stress, experimentally determined in both phases. It was found that during plastic deformations, the von Mises stress does not change significantly in ferrite compared to an important increase in elastically deformed cementite. Therefore, the partitioning of stresses between phases is mainly responsible for the strain strengthening of the tested pearlitic steel exhibiting fully lamellar microstructure.

Acid resistance enhancement of human tooth enamel surface by Nd:YAG laser and incorporating silver nanoparticles: in vitro study

This work was devoted to assess the use of Nd:YAG laser with and without nanosilver particles to enhance tooth resistance of dental enamel against carries. Forty-eight tooth samples were randomly divided into three main groups and received different treatments. Samples of group 1 were illuminated by a single pulse at different laser fluences, while those of group 2 received different number of laser pulses at fixed laser fluence, and finally the samples of group 3 received laser and colloidal silver nanoparticle treatments at different conditions. The samples were subjected to Vickers microhardness test, atomic force microscopy analysis, scanning electron microscopy observation, energy dispersive spectroscopy investigation, and demineralization and re-mineralization tests. Due to fast laser heating and quenching, a significant microhardness increase in the treated dental enamel samples was seen. This resulted in an improvement in the enamel resistance against acids because of the decrease in hydroxyapatite lattice stress and the reduction in enamel solubility. The addition of silver nanoparticles to the laser-treated enamel surface helped stabilize the granules of the enamel surface tissue under the effect of laser irradiation. The demineralization of laser-treated samples showed higher Ca/P ratios than control group, indicating a higher resistance against acids. The combined laser illumination and the addition of silver nanoparticles lowered the tooth abrasion degree and increased tooth resistance to decay. The demineralized samples of all laser-treated samples had higher Ca/P ratios compared to the demineralized control sample. Laser energy has modified the Ca/P mineral ratio and forms steadier and lesser acid soluble compositions.

Yolk-shell manganese oxide nanostructures for lithium-ion battery anodes

Nowadays, anodes based on graphitic materials are struggling with the ever-stringent requirements on lithium ion batteries (LIBs) in terms of energy and power densities, life-span, and deformability, from their extended applications such as automobiles, power grids and wearable electronics. As one of the promising alternates, transition metal oxides (TMOs) hold great perspectives. Unlike the lithium insertion mechanism of graphite, the lithiation/delithiation of TMOs is through redox conversion, imparting higher capacity and better safety. Among the numerous TMOs that have been extensively studied for LIB anodes, manganese oxides (MnO x ) are particularly attractive due to their high natural abundance, environmental benignity, tunable oxidation states, and low fabrication costs. However, as common to most of the TMOs, MnO x are essentially non-conductive and suffer from severe volume expansion upon lithiation, which greatly limit their rate capability and cycle performance. To overcome the above problems of MnO x (as well as other TMOs), many solutions have been attempted and can be majorly classified into two strategies: nanostructuring and carbon-compositing. The former based on developing diverse nanostructures brings in numerous benefits such as shortened ion diffusion path, enlarged electrochemically active surface, promoted electrolyte infiltration, as well as relieved lattice stress. The later based on hybridizing with various kinds of carbonaceous materials enables to greatly enhance electronic conductivity, buffer the cyclic volume fluctuation, and reinforce the electrode stability by providing structural supports for the active materials. Of the explored nanostructures, the yolk-shell structure has gained increasing attentions due to the prominent advantages in buffering the volume expansion and promoting the utilization of active materials. On one hand, when compared to solid nanoparticles the void spaces in the yolk-shell structure can accommodate the cyclic volume change during charge/discharge, effectively preventing the pulverization of active materials. On the other hand, in comparison to the hollow nanospheres and nanocages, the volumetric specific capacity of the yolk-shell structure is obviously superior. Nevertheless, despite of these apparent benefits, previous reported fabrications of yolk-shell nanostructures have been quite complex and typically involved multi-step synthesis with both high material and energy inputs. Besides, the structural stability and integrity of the yolk-shell structure itself pose an issue, in which the nanostructures might crack and collapse due to mechanical stress, especially in the prolonged charge/discharge process. Therefore, a rational design and facile fabrication of yolk-shell nanostructures for optimizing their utilization and stability in LIB anodes are highly desired for achieving the outstanding electrochemical and cycle performance. In this paper, a simple method involving polypyrrole-coated metal organic framework is adopted to synthesize manganese oxides with yolk-shell structure and use them as the anodes for lithium ion batteries. The as-prepared yolk-shell MnO x nanoparticles exhibit good specific capacity during charge/discharge, and demonstrate high specific capacities of 723, 651, 384 mAh g–1 at current densities of 0.1, 0.5 and 2 A g–1, respectively. Great stability and rate performance are also achieved with minimal capacity attenuation for over 200 cycles. Both the fabrication methodology and electrochemical understandings gained here for nanostructured manganese oxides can also extend to the other TMOs towards their ultimate implementation in high-performance LIBs.

Effect of pH on the crystallite size, elastic properties and morphology of nanostructured ZnS thin films prepared by chemical bath deposition technique

Zinc Sulphide thin films have been fabricated on glass substrate via chemical bath deposition technique using zinc acetate, thiourea as the precursor of zinc and sulfur and ammonia for varying pH. The X-Ray diffraction patterns indicate the nanocrytalline nature of the films with broadening of diffraction peaks. Effective Mass Approximation, Scherrer Method and Williamson-Hall plots have been employed for determining crystallite size. The calculated crystallite sizes correlate well with the estimated crystallite sizes from High Resolution Transmission Electron Microscopy images. The HRTEM images show clear lattice fringes of nanocrystallites overlapping each other with random orientations. The elastic properties such as lattice strain, stress and energy density of ZnS thin films have been calculated from the modified form of Williamson-Hall analysis namely Uniform Deformation Model, Uniform Stress Deformation Model, and Uniform Deformation Energy Density Model. The Scanning Electron Microscope images indicate the granular texture of synthesized ZnS thin film at pH 9.6 and coagulation of granules into larger one with increase of pH. The results reveal the obvious effect of ammonia concentration on the optical properties, crystallite size, elastic properties and morphology of the surface of the films.

Hall-Petch relationship and corrosion behavior of cold-rolled CoNiFe medium entropy alloy

CoNiFe medium entropy alloy samples are synthesized by vacuum arc melting and subsequent thermo-mechanical processing. The fully-recrystallized face-centered-cubic (FCC) single phase microstructures with grain sizes ranging from 10 to 100 μm are obtained by annealing processes and the grain growth kinetics and Hall-Petch relationship are investigated. The activation energy for grain growth is 153.9 kJ mol−1 and the recrystallized sample processed at 700 °C possesses superior mechanical properties including high strength and ductility. The lattice friction stress is 168.4 MPa which is larger than that of the CoNiCrFeMn high entropy but less than that of the CoNiCr medium entropy alloy. In addition, in order to investigate the effect of solution temperature on corrosion behaviors of CoNiFe MEA, electrochemical tests in NaCl/H2SO4 solution with different temperature are carried out. The electrochemical experiments show corrosion current density increases and corrosion potential decreases, indicating the corrosion resistance of CoNiFe MEAs in NaCl and H2SO4 solution is weaken with increasing solution temperature.

Valent control and spectral tuning by cation site engineering strategy in Eu doped Sr1−xBaxAl2Si2O8 phosphor

Control of Eu valence is one of the main issues to obtain mixed−valent Eu2+/3+ co−doped phosphor with flexible−tunable emission spectra. In this study, for the first time, we report a simple single cation substitution strategy for controlling Eu valence. The structure of Sr1−xBaxAl2Si2O8 host was tailored by Ba2+ substitution for Sr2+ ions. The lattice parameters show a linear evolution with increase in Ba2+ amount. Correspondingly, the Eu3+ emission intensity also increases over Ba2+ amount. The spectral variation was considered to be attributed to the suppression of Eu3+ reduction by the lattice stress, which is introduced by ion substitution. Finally, valence control of Eu and spectral tuning of Eu3+/2+ co−doped Sr1−xBaxAl2Si2O8 phosphor were realized by the proposed strategy. This study will open a novel avenue for Eu valence control and spectral tuning of mixed–valent Eu doped phosphors.

Structural, morphological, thermal and optical investigations on Mn doped GdCrO3

Perovskite-type GdCr1-xMnxO3 (0.0 ≤ x ≤ 0.4) nano-crystalline samples are synthesized using sol-gel auto combustion process. The effect of Mn-doping in GdCrO3is investigated in term of structural, morphological, optical and thermal properties. X-ray diffraction (XRD) patterns confirm orthorhombic crystal structure of all the samples. The lattice parameters bond lengths and bond angles as obtained from Rietveld refinement analysis are found to vary systematically with Mn concentration. The crystallite sizes as calculated from the Scherrer's equation are found to decrease with Mn content. The Williamson-Hall (W–H) analysis reveals that the crystallite sizes decrease whereas lattice strain, stress, and energy density become more with the increase in Mn doping except for x = 0.3.The particle size estimated using transmission electron microscopy (TEM) are consistent with that obtained through W–H analysis. Scanning electron microscopy (SEM) images with energy dispersive x-ray (EDX) analysis exhibit significant change in the surface morphology with Mn doping and ensure the elemental compositions of the samples. The Fourier transform infrared (FTIR) spectra of these samples confirm the formation of desired crystal structure with two main characteristic bands at 476 and 586 cm−1. The optical band gap is found to reduce whereas Urbach energy increases with the increase in Mn concentration. The values of refractive index decrease in the ultraviolet region as a function of wavelength for all the samples and minimizes at the main absorption peak position as observed in the UV/Vis. spectra. The value of heat capacity at constant pressure (Cp) decreases with Mn doping except for 30% Mn concentration. Therefore, the present investigation suggests that the properties of GdCrO3 system can be tuned with the appropriate doping of Mn for the potential applications.

Enhanced numerical design of two-barrier infrared detectors with III\u2013V compounds heterostructures considering the influence of lattice strain and misfit dislocations on the band gap

The goal of this work is the design of efficient infrared radiation detectors based on InAsSb compounds with two energy barriers around the absorber region. Two types of two-barrier detectors that work in the 3–5.5 μm wavelength range at 230 K is designed. Using our computer program to iteratively solve the Poisson equation, the spatial distribution of energy band edges in III–V heterostructures was calculated The influence of lattice stress, bending of the structure and doping on the energy shift of the edge of the bands is considered. Lattice strain is the cause of the formation of the misfit dislocations at the boundaries of the individual layers of the heterostructure. These dislocations partially relax the resulting stress and affect the lattice deformation in individual layers. From the minimum elastic energy condition, the density of these dislocations is determined. It has been shown that the band offset can be eliminated in the areas of both barriers in the designed two-barrier detectors.

Lead-free high Tc ferroelectric material: Hierarchical Dy-doped ZnO architectures co-assembled by 1D nanorods and 2D nanosheets

High temperature ferroelectricity (Tc ∼435 °C, Ec ∼6.15 kV/cm & Pr ∼0.16 μC/cm2) was observed in a novel 3D hierarchical dysprosium (Dy)-doped ZnO nanorods-nanosheets (NRs-NSs) architecture synthesized using wet chemical co-precipitation method. Such a conclusion was drawn on the experimental confirmation obtained from the temperature variation of real part of dielectric constant and the room temperature P–E hysteresis loop. Dy3+ doping strongly modified the morphology of ZnO from nanotaper to hierarchical NRs-NSs architecture. Lattice strain (ε), crystallite size (L), deformation stress (σ), and deformation energy density (u) of both pristine nanotapers and 3D hierarchical Dy-ZnO NRs-NSs architectures were evaluated using line broadening analysis followed by the Debye-Scherrer and Williamson-Hall methods. Temperature variation of real component of dielectric constant (ε′) for Dy-doped ZnO NRs-NSs architecture attains a maxima (ε′m ∼34,500) at ferro-to para-electric transition temperature, Tc ∼435 °C. Temperature dependent complex component of dielectric constant (ε''), tangent dielectric loss (tan δ) and ac conductivity (σ) were found to increase with rise in temperature. The frequency dependent dispersion plots of dielectric properties of Dy-ZnO NPs showed a decrease in dielectric constant and tangent loss with increase in frequency whereas ac conductivity showed an opposite trend. The Dy-doped ZnO NRs-NSs architectures exhibit feeble ferroelectricity with a remnant polarization (Pr) of 0.16 μC/cm2 and a coercive field (Ec) of 6.15 kV/cm at room temperature. Moreover, the novel Dy-doped nanorods-nanosheets architectures with high temperature ferroelectricity will pave the pathway towards designing futuristic material in the field of low-power and wide-temperature ferroelectric based memory devices.

Determination of compressive strength of 3D polymeric lattice structure as template in powder metallurgy

Powder metallurgy has been developed to fabricate metal foams from various materials including magnesium. One particular challenge on powder metallurgy is fabrication of highly-ordered and interconnected porous products. Pores interconnectivity is important in application of porous magnesium alloy for biodegradable orthopedic implants. Meanwhile, 3D polymeric printing technology offers capability to build precise and rapid lattice wireframe products in a simple and low-cost manner. Here, we design and validate the capability of 3D polymeric lattice as template in powder metallurgy for fabrication of magnesium-based biodegradable implants. Lattice structures were made of ABS, PLA, and PVA filaments. Lattice structures were cubical-shaped with uniform dimension and variations in pore size are included in the study. Both computational and experimental tests are performed to determine the compressive strength of the lattice structures. Uniaxial stress with uniform magnitude is applied to test the lattice structures. The resulting stress, strain, and deformation of the 3D polymeric lattice are observed. Variations in materials and pore size affect the stress, strain and deformation of the 3D polymeric lattice. Parameters can be further optimized to meet the requirement of the design and fabrication process in consideration of the tolerable stress, strain and deformation.

Hydrogen Embrittlement and Improved Resistance of Al Addition in Twinning-Induced Plasticity Steel: First-Principles Study.

Understanding the mechanism of hydrogen embrittlement (HE) of austenitic steels and developing an effective strategy to improve resistance to HE are of great concern but challenging. In this work, first-principles studies were performed to investigate the HE mechanism and the improved resistance of Al-containing austenite to HE. Our results demonstrate that interstitial hydrogen atoms have different site preferences in Al-free and Al-containing austenites. The calculated binding energies and diffusion barriers of interstitial hydrogen atoms in Al-containing austenite are remarkably higher than those in Al-free austenite, indicating that the presence of Al is more favorable for reducing hydrogen mobility. In Al-free austenite, interstitial hydrogen atoms caused a remarkable increase in lattice compressive stress and a distinct decrease in bulk, shear, and Young’s moduli. Whereas in Al-containing austenite, the lattice compressive stress and the mechanical deterioration induced by interstitial hydrogen atoms were effectively suppressed.