Properties Of Metallic Materials Research Articles

A novel apparatus dedicated to the estimation of the thermal diffusivity of metals at high temperature

In order to characterize thermophysical properties of high conductivity metallic materials, this work proposes a novel experimental apparatus supported by an analytical solution and a numerical simulation. The experimental set-up measures simultaneously the temperature evolutions on both the front and rear faces of a sample using a single detector following the high-speed thermography principle through a dedicated system of six mirrors. This innovative configuration allows to reach high temperatures in a controlled atmosphere without pollution by contact. A transient 2D-axisymmetric model is developed, considering heat transfer along the radius and thickness directions. In a first stage, the model is compared to a finite element model, then the estimation procedure is validated by a noised direct model. Afterwards, the experimental temperatures versus time are used to estimate the thermal diffusivity of pure iron and stainless steel 304 in the solid state at high temperature in a pollution-free environment. The estimated values for a temperature range between 1300 K and 1600 K are then compared with published data.

Design of synergistic alloying CoCrFeNi eutectic high entropy alloy based on infinite solid solution

Multivariate synergistic alloying is an effective means to improve the comprehensive mechanical properties of metallic materials. Eutectic high-entropy alloys achieve heterogeneous biphasic layered structures on the micro and nano scale resulting in very good properties, most of the current alloying studies of CoCrFeNi eutectic high-entropy alloys focus on unitary alloying. In this work, the design strategy of CoCrFeNi eutectic high-entropy alloys based on infinite solid solution synergistic alloying is proposed, and a series of eutectic high-entropy alloys consisting of face-centered cubic (FCC) and intermetallic compound (IM) with fine and regular microstructures are successfully designed, and some of the synergistic alloying eutectic high-entropy alloys have very excellent comprehensive mechanical properties.

Effects of external loads on microstructure and properties of P92 steel

During the metal-solid phase transition, the mechanical properties of metal materials are affected by the nucleation rate and growth rate of grain. In this work, external loads (200 N, 400 N, 600 N, and 800 N) were applied to P92 steel during the heat treatment process in an attempt to improve and optimize the microstructure and mechanical properties of P92 steel. The effects of different external loads on the morphology, corrosion resistance, microhardness, and mechanical properties of P92 steel were investigated by using optical microscopy, microhardness testing, electrochemical testing, tensile strength measurements, and semi-automatic impact tester. The results show that the grain growth rate of P92 steel was moderate under an external load of 600 N; the grain distribution was uniform and orderly whereas the microhardness and corrosion resistance of the sample reached the optimum value (528 Hv). The tensile strength, yield strength, and elongation of the sample were 786 MPa, 525 MPa, and 37.8 %, respectively. However, the impact power of the P92 steel under an external load of 200 N was the minimum, and its average value was 132 J. The results depict that the external load can improve the mechanical properties of P92 steel.

Coercive Force of Low-Carbon Steel Specimens Subjected to Cyclic Loading and Impulse Current

The change in the coercive force of the 10kp5 steel specimens subjected to cyclic loading and impulse current has been studied. The choice of processing methods, including their combination in a certain sequence, was shown to provide the best plastic or strength properties of metal materials. The feasibility and good perspectives of express assessment of the effectiveness of the chosen method or methods of processing metal materials by magnetic properties, e.g., coercive force, without resorting to mechanical tests with the destruction of specimens, are noted. The highest changes towards increase in strength and coercive force in the 10kp5 low-carbon steel have been found after cyclic loading and in a combined mode with cyclic loading at the final stage. The optimal combination of cyclic loading and pulse current can make it possible to control the strength and magnetic properties of ferromagnetic materials.

Data-driven time–frequency analysis of nonlinear Lamb waves for characterization of grain size distribution

Nondestructive characterization of grain size distribution is significant for revealing the mechanical properties of metal materials. Traditional linear ultrasonic methods have been applied to estimate mean grain size but are less sensitive to small grain size. Nonlinear ultrasonic technology shows high sensitivity to microstructures, while it unfortunately encounters underdetermined problem in the characterization of microstructures across multiple scales. Combining linear and nonlinear ultrasonic responses would be a quite attractive way to achieve comprehensive observation of microstructural evolution. This work presents a data-driven approach for characterizing grain size distribution using nonlinear Lamb waves. The short-time Fourier transform (STFT) of detected ultrasonic signals were input into a convolutional neural network (CNN) to comprehensively learn the implicit linear and nonlinear dynamics involved with grain size distribution. Multiple convolution kernels slide across the STFT images with multiscale receptive fields to collectively model hierarchical representations and capture local correlation of interesting from time-frequency domain. The trained model achieved 94.7% accuracy in predicting mean grain size, and also achieved 95.4% and 86.3% accuracy in predicting the expectation and standard deviation of the lognormal distribution of grain size, respectively. The visual activation maps demonstrate that local interesting features are successfully captured. In particular, the prediction accuracy was demonstrated to reduce greatly after removing the fundamental frequency and second harmonic from the STFT images, confirming that incorporating linear and nonlinear ultrasonic information is indispensable for accurate characterization of grain size distribution.

In situ synthesis of N-containing CoCrFeNi high entropy alloys with enhanced properties fabricated by selective laser melting

Although there have been extensive studies on CoCrFeNi high entropy alloys (HEAs), they are still far from industrial applications due to their inferior strength. Based on the approach of interstitial atom strengthening which has been shown to be one of the effective ways to modify the properties of metallic materials, a series of (CoCrFeNi)100-xNx (x = 0, 0.25 and 0.50 at. %) HEAs were prepared in this study by selective laser melting (SLM). It was found that nitrogen addition in CoCrFeNi HEA can slightly refine the microstructure but did not change the preferred orientations after SLM. By increasing the nitrogen content in the matrix, the strength increases while the ductility is reduced. Also, the addition of nitrogen in CoCrFeNi HEA can decrease the stacking fault probability, leading to the increased stacking fault energy (SFE) in N-doped CoCrFeNi HEA. The increased strength in N-doped CoCrFeNi HEA samples mainly attributes to the solid solution strengthening of nitrogen, whereas the ductility loss results from the impediment on the formation of deformed twins induced by increased SFE. These results can provide a new strategy for designing high-strength N-doped HEAs.

Ultra-fast amorphization of crystalline alloys by ultrasonic vibrations

• A facile and rapid solid-state amorphization method was discovered. • The tuning of amorphous content was achieved. • Ultrasonic vibration method exhibits an outstanding time advantage than other methods. • The elements redistribute uniformly and rapidly under ultrasonic vibration. • A new order-disorder transition mechanism was introduced. The amorphization of alloys is of both broad scientific interests and engineering significance. Despite considered as an efficient strategy to regulate and even achieve record-breaking properties of metallic materials, a facile and rapid method to trigger solid-state amorphization is still being pursued. Here we report such a method to utilize ultrasonic vibration to trigger amorphization of intermetallic compound. The ultrasonic vibrations can cause tunable amorphization at room temperature and low stress (2 MPa) conveniently. Remarkably, the ultrasonic-induced amorphization could be achieved in 60 s, which is 360 times faster than the ball milling (2.16 × 10 4 s) with the similar proportion of amorphization. The elements redistribute uniformly and rapidly via the activated short-circuit diffusion. Both experimental evidences and simulations show that the amorphous phase initiates and expands at nanograin boundaries, owing to the induction of lattice instability. This work provides a groundbreaking strategy for developing novel materials with tunable structures and properties.

Laser Powder Bed Fusion of Dissimilar Metal Materials: A Review

The laser powder bed fusion (LPBF) technique is used to manufacture complex and customised components by exploiting the unique advantages of two types of metal materials to meet specific performance requirements. A comprehensive overview of LPBF-processed dissimilar metal materials, a combination of different single metals or alloys, is developed. The microstructure in the fusion zone and the corresponding mechanical properties of LPBF-processed dissimilar metal materials are summarised. The influence of processing factors on the mechanism of defect formation, wetting properties and element diffusion behaviour at the interface between different materials and their typical cases are scientifically investigated in detail. Particular attention is paid to energy input, Marangoni convection and interfacial bonding behaviour. The underlying science of the metallurgical structure and properties of the LPBF-processed dissimilar metal materials is revealed. The build quality and efficiency could be further improved by designing machine structures and predicting the process-property relationship. This review provides a significant guide for expanding the industrial application of LPBF-processed dissimilar metal materials.

Specimen geometry design for plasticity and fracture characterization of sheet metal under high testing speed and various stress states

To model a vehicle crash event using the finite element (FE) method, accurate material properties of automotive sheet metals at high strain rates and various stress states need to be known. In this paper, a series of specimen geometries were designed for dynamic tensile tests in a servo-hydraulic tensile machine to get rid of the system ringing effect. These specimen geometries, which consist of different Stress triaxialities and Lode angle parameters, were optimized according to a similar physical principle as that used for the Gen. III specimen of Fang and Grams using FE simulations. Oscillation-free forces were obtained during the high-speed tests in the strain rate range of up to 103 s−1 using specimens that have a novel design. The deformation and local strain fields of the specimens were measured using digital image correlation (DIC) techniques. Furthermore, the deformation and fracture behavior of a micro-alloyed steel (H340) were characterized and analyzed. The determination of the model parameters for plasticity, damage/fracture modeling, and the material’s strain-rate dependency could be conducted more accurately based on the improved oscillation-free force measurements, which resulted in an improved prediction of the plasticity and fracture behavior of the investigated steel.

Technological Aspects in Fatigue Design of Metallic Structures

Traditional manufacturing processes, such as welding and casting, and modern techniques, such as additive manufacturing, can significantly affect the local material properties of metallic materials [...]

Simultaneously optimizing the strength and ductility of high-entropy alloys by magnetic field-assisted additive manufacturing

The mechanical properties of many metallic materials have been optimized by magnetic field-assisted additive manufacturing, however, there is still a gap in high-entropy alloys (HEAs) in this field, which is not conducive to the control and optimization of the microstructure and properties of HEAs. This work studied the tensile properties of laser powder bed fusion (LPBF) CoCrFeMnNi HEA. After applying a magnetic field, the relative density increased, and the grain size became larger and more uniform. Because of amperage force, crystallographic textures gradually change from< 100 > to< 110 > and< 111 > , which contributes to the improvement of tensile properties. Additionally, low-angle grain boundaries and geometrically necessary dislocations decrease, while the Schmidt factor increases. In the results of these changes, most factors contribute to improving the mechanical property, eventually optimizing the strength and ductility simultaneously. This indicates that magnetic field-assisted LPBF is promising to be an important means to optimize the mechanical properties of HEAs.

Exploring nonlinear strengthening in polycrystalline metallic materials by machine learning methods and heterostructure design

To improve the strength and plasticity of structural materials, researchers often introduce various strengthening mechanisms such as second-phase strengthening, dislocation strengthening, and back stress strengthening (HDI). Due to the interaction of multiple mechanisms, the linear superposition relationship has a poor fitting effect and is only used for rough calculations of the strengthening mechanisms. In this study, the transfer learning data was used to optimize the deep learning network structure (Re-CNN) based on the residual algorithm, and the yield strength prediction physical neural informed model (PNIM) of polycrystalline metallic materials was established. To promote the industrial application of the heterostructure design method, a medium carbon steel heterostructure design strategy based on the existing equipment of the factory was proposed. Medium-carbon heterostructure materials (MHSM) with mixed strengthening mechanisms were successfully prepared. MHSM exhibits excellent comprehensive mechanical properties. When a linear relationship is used to describe the MHSM yield strength, there is a large error, while Re-CNN shows satisfactory prediction accuracy. The linear relationship is incompatible with homogeneous structure materials and heterogeneous structure materials, and its universality is lower than that of nonlinear Re-CNN. Re-CNN shows high cross-scale prediction ability and can be compatible with homogeneous microstructures and heterogeneous microstructures. Using the heterogeneity evolution characteristics of MHSM, the key factors deviating from the linear relationship were revealed. The overestimation and underestimation of the linear relation are demonstrated by Taylor factor and TEM analysis to be caused by the multiscale properties of ferrite, the behavior of the second phase particles, and the interaction of various mechanisms. This study provides a new idea for the cross-scale calculation of the mechanical properties of polycrystalline metallic materials.

Controlling diffusion in gold bonding materials for high reliability via microalloying of trace rare earth metals

Diffusion plays a vital role in regulating microstructure evolution and properties of metallic materials. However, understandings of how microalloying affects diffusion kinetics in gold bonding materials remain far from comprehensive, which severely threatens the reliability of microelectronic devices in the big-data era. This problem persists challenging due to enormous difficulty in accurate and cost-effective experimental measurements. Here, first-principle based theoretical computations are performed to explore the control of diffusion at elevated service temperatures by trace rare earth (RE) microalloying in gold bonding materials. We identify the light lanthanides can stably bind excess vacancies and the efficacy to modulate vacancy/solute-vacancy evolution depends on the RE concentrations and ambient temperatures. Above critical doping concentrations, self- and impurity-diffusion can be simultaneously hindered. These findings successfully point to a rational microalloying strategy to withstand heat and a novel perspective on improving the service life-time of microelectronics packaging materials.

Magnetic Field‐Assisted Laser Shock Peening of Ti6Al4V Alloy

Laser shock peening is widely used in mechanical property improvements of metallic materials. One concerning factor is the nonuniformity of mechanical properties and microstructures, such as surface hardness and grain refinement. Herein, a new strengthening strategy that integrates femtosecond laser shock peening and pulse magnetic field that can uniformize the performance of metallic materials is proposed. With the magnetic field‐assisted laser shock peening (MFLSP), the reduction of preferred‐clustering points shows uniform grain refinement with the maximum area fraction of small grains. The fabrication of uniform grain refinement is attributed to the dislocation redistribution by the release of pinning effect. With magnetic field stimulation, dislocation lines are observed to disperse from low‐angle grain boundary to the intragranular area. Dislocation behaviors stimulated by magnetic field are attributed to atomic migration. The dispersed dislocations serve as potential glide sources for grain refinement during laser‐induced plastic deformation. The enhanced grain refinement results in uniform surface hardening of metallic materials. The application of this integrated strategy with laser processing and external energy field can be used for adjusting mechanical properties of metallic materials with uniform microstructures and surface hardness.

Failure Analysis of Ф73.02 mm × 5.51 mm S13Cr 110 Tubing Collapse in an Oil Field

The field service conditions of a well’s collapse tubing were investigated, and the physical and chemical properties of metal materials (chemical composition analysis, mechanical property test, metallographic structure analysis of tubing materials), hydrogen sulfide stress corrosion cracking test of tubing materials, and scanning electron microscopy analysis of tubing cracks and fracture surfaces were tested in this paper. The results show that the major cause of tubing collapse is that the tubing material is super 13Cr (S13Cr). When it is used in the environment containing hydrogen sulfide, plenty of longitudinal stress corrosion cracks is generated on the inner wall, which greatly reduces the actual anti extrusion ability of the tubing. During the gas lift of the well in the later stage, the upper part of the oil pipe was blocked and the oil jacket was in series, and the gas lift pressure was transmitted into the oil jacket annulus, so that the pressure difference between the inner and outer parts of the oil pipe exceeded its actual anti extrusion capacity and collapse failure occurred.

Recent Advances in Liquid Metal Photonics: Technologies and Applications.

Near-room-temperature liquid metals offer unique and crucial advantages over solid metals for a broad range of applications which require soft, stretchable and/or reconfigurable structures and devices. In particular, gallium-based liquid metals are the most suitable for a wide range of applications, not only owing to their low melting points, but also thanks to their low toxicity and negligible vapor pressure. In addition, gallium-based liquid metals exhibit attractive optical properties which make them highly suitable for a variety of photonics applications. This review summarizes the material properties of gallium-based liquid metals, highlights several effective techniques for fabricating liquid-metal-based structures and devices, and then focuses on the various photonics applications of these liquid metals in different spectral regions, following with a discussion on the challenges and opportunities for future research in this relatively nascent field.

Hardness-thermal stability synergy in nanograined Ni and Ni alloys: Superposition of nanotwin and low-energy columnar boundary

• A series of highly oriented NT Ni and Ni alloys are fabricated by electrodeposition. • The NT Ni and Ni alloys exhibit superior combinations of high hardness and good thermal stability. • The low driving force for grain growth induced by the low-angle columnar boundary architecture contributed to superior thermal stability for NT Ni. • Minor Re/Mo solutes provide an additional pinning effect on the migration of twin/columnar boundaries. Refining grains into nanoscale can significantly strengthen and harden metallic materials; however, nanograined metals generally exhibit low thermal stability, hindering their practical applications. In this work, we exploit the superposition of the contribution of nanotwins, low-angle grain boundaries, and microalloying to tailor superior combinations of high hardness and good thermal stability in Ni and Ni alloys. For the nanotwinned Ni having a twin thickness of ∼2.9 nm and grain size of 28 nm, it exhibits a hardness over 8.0 GPa and an onset coarsening temperature of 623 K, both of which are well above those of nanograined Ni. Re/Mo microalloying can further improve the onset coarsening temperature to 773 K without comprising hardness. Our analyses reveal that high hardness is achieved via strengthening offered by extremely fine nanotwins. Meanwhile, the superior thermal stability is mainly ascribed to the low driving force for grain growth induced by the low-angle columnar boundary architecture and to the additional pinning effect on the migration of twin/columnar boundaries provided by minor Re/Mo solutes. The present work not only reveals a family of nanotwinned metals possessing the combination of ultra-high hardness and high thermal stability but also provides a strategy for tailoring properties of metallic materials by pairing low-angle grain boundaries and twin boundaries.

Toward Material Property Extraction from Dynamic Spherical Indentation Experiments on Hardening Polycrystalline Metals

Static indentation and dynamic indentation are reviewed, with a focus on extraction of material properties of isotropic strain-hardening polycrystalline metals that may be rate- and temperature-sensitive. Static indentation is reviewed first, followed by dynamic indentation, since the former is regarded as a specialization of the latter with inertia, rate dependence, and adiabatic heating excluded. Extending concepts from the literature review, a treatment of dynamic indentation using dimensional analysis is forwarded, and a general framework for extraction of material property information (i.e., constitutive model parameters) from instrumented dynamic spherical indentation experiments is set forth. In an example application of the methodology, experimental data obtained from instrumented spherical indentation in a miniature Kolsky bar apparatus are evaluated via dimensional analysis. The substrate material is aluminum alloy Al 6061-T6. Several definitions of indentation strain proposed for static indentation are assessed for dynamic indentation, as are indentation strain rates. While the fidelity of the experimental method and inertial effects could inhibit extraction of elastic properties, extraction of certain plastic constitutive properties may be feasible. Current data are insufficient to enable determination of a complete and unique set of all physical properties. Motivated by the present review and analysis, new experiments and simulations are proposed that would identify influences of material properties, facilitating their extraction from data.

A numerical study of enhanced lithium-ion battery cooling using a module insert

Thermal performance of an electric vehicle (EV) battery module with an integrated cooling insert was numerically analyzed using computational fluid dynamics (CFD). Twelve NCM prismatic cells were packaged into a module where each cell was physically isolated from its neighboring cells by the cooling insert, designed to enhance the module’s thermal performance. The battery cells and the cooling insert were attached to a thermal interface material (TIM) and a cooling plate with integrated liquid cooling where the coolant was a 50/50 ethylene glycol water (EGW) mixture. A heat generation model based on the discharge rate was used to assess the thermal responses of the module such as heat flux and temperature distribution. Thermal characteristics were studied under various discharge rates, coolant flow rates, insert thicknesses and material conditions. Results showed that the cooling insert reduced the cell temperature by 1.4 °C and increase the heat flux by 15.6% at 3 mm thickness with a coolant flow rate of 4 L/min. Cooling plates with plastic and metallic material properties were also studied and temperatures reductions up to 0.7 and 1.0 °C were observed, respectively. Furthermore, temperature uniformity was maintained to within 0.3 °C across all twelve cells at a coolant flow rate of 9 L/min. The results of this study could potentially lead to the development of a compact and low-cost intra-cell heat spreader in a battery module that can be readily implemented in production EVs.

Layer thickness dependent plastic deformation mechanism in Ti/TiCu dual-phase nano-laminates

Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials, but the underlying deformation mechanism is still under the way of exploring. Here, the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates (DPNLs) with different layer thicknesses are investigated using molecular dynamics simulations. The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible, while it affects the plastic deformation mechanism of amorphous layers distinctly. The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs, which is inversely proportional to the layer thickness. It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat. Young’s moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces. Furthermore, the main plastic deformation mechanism in crystalline part: grain reorientation, transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti, has also been displayed in the present work. The results may provide a guideline for design of high-performance Ti and its alloy.