Behavior Of Metallic Materials Research Articles

Effects of Notches and Defects on Dwell Fatigue Mechanism and Fatigue Life of Ti-6Al-4V ELI Alloy Used in Deep-Sea Submersibles

The notch (i.e., stress concentration) and defect are important factors influencing the conventional fatigue behavior of metallic materials. What is the influence of notches and defects on the dwell fatigue mechanism and fatigue life? In this paper, the effects of notches and defects on the dwell fatigue behavior of the Ti-6Al-4V ELI alloy used in deep-sea submersibles are investigated under the load control mode. It is shown that the dwell fatigue is insensitive to the defect size (190–438 μm) compared to the conventional fatigue. For notched specimens, they all present fatigue failure mode under dwell fatigue testing, and the dwell fatigue life is higher than that of the smooth specimen at the same local maximum stress. The dwell of the maximum stress has no influence on the fatigue life and failure mechanism for notched specimens. Moreover, the facet feature is observed in the crack initiation region for both the conventional and dwell fatigue of notched specimens. Electron backscatter diffraction observation indicates that the feature of the fine line markings on the facet in the image by scanning electron microscope is due to the steps on the fracture surface of the α grain.

Influence of grain refinement on the corrosion behavior of metallic materials: A review

Influence of grain refinement on the corrosion behavior of metallic materials: A review

A new macroscopic strain hardening function based on microscale crystal plasticity and its application in polycrystal modeling

A new phenomenological strain hardening function is proposed to describe the strain hardening behavior of metallic materials. The function is based on a simplification of an earlier established self and latent hardening crystal plasticity approach. The proposed function contains only four parameters, which can be readily obtained using an efficient numerical technique by fitting the experimental curve. Several applications on different materials are presented and good agreements with the experimental counterparts were obtained. One great advantage of the proposed empirical function is that its parameters can be directly used in polycrystal viscoplastic modeling (VPSC approach) for crystal plasticity-based incremental strain hardening simulations. For the conversion of the parameters between the macroscopic scale and the grain-level, the Taylor factor was used, which was re-defined for polycrystals in the present work. The VPSC simulations also led to good reproduction of the experimental strain hardening behavior for all investigated cases, with rapid convergence.

Recent progress on the corrosion behavior of metallic materials in HF solution

Abstract Hydrofluoric acid (HF) or fluoride ion corrosion issues are often encountered in many fields, which have attracted extensive research due to its strong corrosiveness. In this paper, a critical review is presented based on recent progress on HF corrosion. In view of the discrepancy of fluoride ion compared with other ions, the special attack characteristics of fluoride ion are firstly discussed. Afterwards, the corrosion mechanisms of stainless steels, nickel-based alloys, and titanium alloys in HF solution or fluoride ion-containing environment are reviewed, and three typical corrosion behaviors are summarized, which are essentially weakening process of passivation of metallic materials. The effects of influencing factors (e.g. alloying elements, environmental factors, and stress, etc.) on HF corrosion are also discussed, which involve changes in passivation mechanism, the influence of HF attack mode and multiple damage mechanisms due to mechanical–chemical coupling. Finally, future research works on HF corrosion are proposed.

A Review: Graphene Modified Polymer Coatings For Corrosion Protection

Environmental and other chemical factors lead to decimated corrosive behaviour of metallic materials that is a severe hazard and an emerging challenge for times. Different protection strategies have been proposed to suppress this problem and among them graphene based coatings are considered to be great technique against corrosive behaviour because of its hydrophobic properties and ability to provide corrosion resistance of composite material. The incorporation of functional nanoparticles can provide the corrosion resistance to mild steel. It regarded a promising nonmaterial in corrosion protection. Present written text focuses on the preventive applications of graphene based nanomaterials, nanocomposites, polymeric coating techniques and their methods to fight the corrosive act of steel.

Deformation behavior during hot processing of the alloy of the Al-Mg system economically doped with scandium

Hot deformation behavior of the new alloy 1580 sparingly doped with scandium (Al-5Mg-0.6Mn-0.10Sc-0.11Zr) was studied under the deformation temperature ranging from 350 to 450 °C and strain rate ranging from 0.01 to 10 s−1. Hot deformation by uniaxial compression and torsion was carried out on a Gleeble 3800 thermomechanical simulator. Hot deformation of the alloy 1580 is accompanied by dynamic softening with the establishment of a balance between the rates of nucleation and annihilation of dislocations. Alloy flow stresses increase with increasing strain rate and decreasing temperature. The experimental results for the new alloy are in full agreement with the known concepts that the combined effect of temperature and strain rate on the deformation behavior of metallic materials is described by the Zener-Hollomon parameter. The deformation activation energy of the alloy obtained by the regression analysis of steady-state flow stresses is 175.7 kJ/mol. When using the steady-state flow stresses normalized to the shear modulus, the deformation activation energy is 148.8 kJ/mol and is close to the activation energy of self-diffusion of aluminum. Analytical expressions are obtained for steady-state flow stresses as a function of the Zener-Hollomon parameter, which make it possible to predict the deformation resistance of the alloy 1580 in a wide range of temperatures and strain rates. This result is important for FEM modeling and for the choice of temperature and stain rate of hot deformation of the alloy under study. Comparison with the literature data showed that in the region of high temperatures and low strain rates, the flow stresses are weakly dependent on the scandium content in the alloy. However, with a decrease in the temperature and an increase in the strain rate, an increase in the scandium content in the alloys leads to a noticeable increase in the flow stresses. In torsion tests, a sharp increase in the ductility of the alloy is observed at a temperature of about 400 °C. One of its probable causes may be dissolution of particles Al3(Sc,Zr) during hot deformation in this high-temperature region.

Prediction of Anisotropic Elastoplastic Instability with Rice’s Criterion in Plane Compression

Objectives: The main objective of this work is the development of a mechanically coherent framework for the implementation of numerical simulation tools for sheet metal forming processes. The work at hand is part of a study of the mechanical behaviour of metallic materials subjected to large elastoplastic deformations during channel-die testing and a study of the mechanisms that limit their formability and cause their instability. We analyse the effect of induced rotation on the appearance of plastic instability predicted by Rice’s criterion. Methods: At the beginning, an adequate modelling of the mechanical behaviour of metals in large elasto-plastic deformations using the formalism in rotational referential is made. Then, a prediction of plastic instabilities is developed using Rice’s bifurcation criterion. Indeed, the integration of the law of anisotropic elastoplastic behaviour is presented in a three-dimensional kinematics framework in order to write the deformation tensor as a superior triangular matrix, with Hill’s anisotropic yielding function, using Runge Kutta’s method to integrate the obtained equations. Findings: we were able to show that Rice’s criterion can be used for any kind of material and that this criterion is effective in predicting what happens in metals. It predicts shear-band bifurcation in a continuous plastic medium. Hill’s criterion is suitable for what is weakly anisotropic. The model described above represents a good mathematical framework for analysing the behaviour of materials and plastic instability. Novelty: This study allows to apply Rice’s criterion in the case of a channel-die compression test, so as to locate plastic instability and see the appearance of shear bands for all types of materials; it demonstrates that the initial rotation of the material influences the appearance of shear-bands during a test simulating rolling. Keywords: Elastoplastic; Large deformations; Anisotropy; Plastic instability; Localisation

Effect of Water Vapor on Alumina Scale Growth Based on First-Principles Calculations

Despite much effort directed at elucidating the impact of water vapor on the high-temperature oxidation behavior of metallic materials, a complete understanding of its atomistic mechanisms remains ...

In-Situ SEM High Strain Rate Testing of Large Diameter Micropillars Followed by TEM and EBSD Postmortem Analysis

BackgroundDislocation dynamic simulations are intended as a tool to understand and predict the mechanical behavior of metallic materials, but its prediction has never been directly verified by experiments due to differences in specimen strain rate and size.ObjectiveIn this work, a comprehensive experimental framework is proposed to attempt direct comparison between experiments and discrete dislocation dynamics (DDD) modelling. MethodsBy integrating high-throughput sample fabrication and a customized testing apparatus, the sample size and strain rate typically employed in DDD simulations are explored experimentally. Constitutive properties such as stress-strain response are measured, and microstructural information is obtained from transmission electron microscopy (TEM) imaging, electron backscatter diffraction (EBSD), and TEM-based orientation mapping. ResultsMagnesium and copper were selected, as case studies, to demonstrate the newly developed experimental procedure. Measured stress-strain responses for Mg are consistent with those obtained with a miniaturized Hopkison bar experiments. By exploiting the validated workflow, the effect of strain rate on micropillar heterogeneous deformation and associated dislocation plasticity were revealed.ConclusionThe work establishes a methodology for the systematic study of not only metals but also other materials and structures at the microscale and high strain rates.

Abrasive and adhesive wear behaviour of metallic bonds in a synthetic slurry test for wear prediction in reinforced concrete

The understanding of the tribological system and the corresponding wear behaviour of metallic materials is, especially in wet condition and in presence of abrasive particles, of high importance. This particularly applies for construction applications, like core drilling and sawing in reinforced concrete, where the knowledge about adhesive wear but also abrasive micro- and macro-mechanisms is limited. If it comes to material removal in reinforced concrete, adhesive wear between the metal matrix and the reinforcement steel is observed, besides abrasive wear as a result of the metal matrix–concrete interaction. To differentiate adhesive and abrasive wear, a new approach for testing metal materials with varying counter parts and different sliding speeds in a wet-slurry test is presented. A for this work modified B611 - 13 test is used to test two different metal compositions to investigate their change in mass, micro-hardness and the microstructure at the sliding interface zone. Additionally, the wear pattern is identified by optical microscope and under the scanning electron microscope. To differentiate the main wear mechanisms, a S355 steel and a silicon carbide ceramic are used as a counterbody. The results show that it is possible to separate the wear behaviour while testing in different conditions.

Hot deformation behavior and processing maps of hybrid SiC and CNTs reinforced AZ61 alloy composite

The hot deformation behavior of hybrid SiC and CNTs reinforced AZ61 alloy composite was investigated by hot compacting at the strain rate range of 10−4–0.1 s−1 and temperature range of 250–400 °C. The constitutive equation and processing maps were successfully established and checked. The results revealed that the composite exhibited typical flow behavior of metallic materials, and the flow stress increased as the temperature decreased and strain rate increased. The flow behavior was precisely described by using hyperbolic sine constitutive equation in this work. The average stress exponent and activation energy of the composite are 4.9 and 174 kJ/mol, respectively, indicating that the dominant deformation mechanism might be dislocation climb. The processing maps of the composite exhibited two instability zones and two safe zones (250–330 °C, 0.001–0.006 s−1 and 350–390 °C, 0.0001–0.0005 s−1) for selection of optimum processing parameters. Dynamic recrystallization (DRX) occurred in the safe zones, however, cracking and twinning were observed in the instability zones. In addition, the examination of microstructure evolution revealed that DRX gradually occurred more adequately as the temperature increased and strain rate decreased, and SiC particulates could promote the DRX of the composite due to the particle stimulating nucleation (PSN) effect.

Efficient parameters identification of a modified GTN model of ductile fracture using machine learning

The ductile fracture behavior of metallic materials is usually coupled with complex stress states. In order to describe the facture behavior of metallic materials under a broad range of stress states, a modified Gurson-Tvergaard-Needleman damage model was proposed by Wei Jiang and has been used to simulate the ductile fracture of 2024-T3 aluminum alloy. However, it was a heavy and trifle job to determine the unknown parameters of the model because of the large number of them and inefficient identification strategy. In this research, we propose an efficient parameters identification strategy of this new damage model based on machine learning algorithm. This strategy combines resilient back-propagation neuro network with genetic algorithm and simulations were implemented in terms of ABAQUS/Explicit. The same strategy of optimization was also used to reduce simulation time. Damage model parameters of 2024-T3 aluminum alloy were identified from the experimental force-displacement curves of the specimens exhibiting high stress triaxiality and negative triaxiality. The identified parameters were verified by using the test results of the specimens providing low and zero stress triaxialities.

Identification methodology of a rate-sensitive constitutive law with mean field and full field modeling approaches for polycrystalline materials

The present paper deals with the consideration of the rate-sensitivity mechanical behavior of metallic materials, in the framework of mean field and full field homogenization approaches. We re-examine the possibility of describing properly this rate sensitivity with a simple and widely used power law expressed at the level of the slip system, and we propose a methodology to accelerate the identification of the global material constitutive law for Finite Element (FE) simulations. For such an aim, simulations of a tensile test are conducted, using a simple homogenization model (the Taylor one, used in a relaxed constraint form) and an FE code (Abaqus), both using the same single-crystal rate-dependent constitutive law. It is shown that, provided that the identification of this law is performed with care and well adapted to the examined case (rate-sensitive or insensitive materials, static and/or dynamic ranges), the simple power law can be used to simulate the macroscopic behavior of polycrystalline aggregates in a wide range of strain rate (including both static and dynamic regimes) and strain-rate sensitivity values (up the rate-insensitive limit).

Heat treatment effect on 17-4PH stainless steel manufactured by Atomic Diffusion Additive Manufacturing (ADAM)

A growing interest is observed in industry for metallic additive manufacturing. Atomic Diffusion Additive Manufacturing (ADAM) is a new extrusion-based process. The mechanical behavior of metallic materials obtained via ADAM has not been analyzed much. In the present work, a microscale experimental investigation was performed to study the behavior of 17-4PH stainless steel. The effect of heat treatment on the mechanical properties of the material was also examined.

A Modified Phase-Field Damage Model for Metal Plasticity at Finite Strains: Numerical Development and Experimental Validation

Steel structures are designed to operate in an elastic domain, but sometimes plastic strains induce damage and fracture. Besides experimental investigation, a phase-field damage model (PFDM) emerged as a cutting-edge simulation technique for predicting damage evolution. In this paper, a von Mises metal plasticity model is modified and a coupling with PFDM is improved to simulate ductile behavior of metallic materials with or without constant stress plateau after yielding occurs. The proposed improvements are: (1) new coupling variable activated after the critical equivalent plastic strain is reached; (2) two-stage yield function consisting of perfect plasticity and extended Simo-type hardening functions. The uniaxial tension tests are conducted for verification purposes and identifying the material parameters. The staggered iterative scheme, multiplicative decomposition of the deformation gradient, and logarithmic natural strain measure are employed for the implementation into finite element method (FEM) software. The coupling is verified by the ‘one element’ example. The excellent qualitative and quantitative overlapping of the force-displacement response of experimental and simulation results is recorded. The practical significances of the proposed PFDM are a better insight into the simulation of damage evolution in steel structures, and an easy extension of existing the von Mises plasticity model coupled to damage phase-field.

An experimental and numerical investigation on impact spot welding of metallic plates using gas mixture detonation technique

In this paper, the impact spot welding of metallic plates was investigated both experimentally and numerically using a single-stage gas mixture detonation apparatus. The impact spot welding process was carried out on aluminum alloy and steel materials using rigid steel projectiles. In this process, the mixture of oxygen and acetylene was detonated in a combustion chamber to launch the projectile. The masses of flat- and spherical-nosed projectiles were 270 and 230 g, respectively. The impact velocity was measured in all experiments. The cross-sections of the weld spots were inspired by a scanning electron microscope to assess the quality of welding. For several experiments, wavy interfaces were observed showing there is a good bonding. For numerical simulation of the process, Abaqus/Explicit software was used and the deformation and failure mechanisms of impact spot-welded specimens were further investigated. The Johnson–Cook thermoplasticity model along with its failure model was utilized to predict the behavior of metallic materials. The numerical simulation results were in good agreement with those obtained from experiments in terms of the deformation mode and failure pattern. The propagation of the wave on the surface of the flyer plate was further studied. The results showed that the stress waves start from the center and propagate to the corners of the plate. To numerically evaluate the welding quality, two parameters of the shear stress at the collision point as well as the equivalent plastic strain for the flyer and target plates were obtained in the numerical simulation. The numerical results showed opposite directions of shear stress for flyer and base plates at the contact point, which can be used as proof for good bonding. Besides, the magnitudes of the equivalent plastic strain for both flyer and base plates were higher than those reported values in the open literature that confirms successful welding.

Dislocation-grain boundary interaction in metallic materials: Competition between dislocation transmission and dislocation source activation

Dislocation transmission across grain boundary (GB) and activation of dislocation source in adjacent grains are considered common features of dislocation-GB interactions in regulating mechanical properties and behaviors of metallic materials and structures. However, it is currently unclear which of dislocation transmission and dislocation source activation plays the dominant role in regulating dislocation-GB interaction. To study the competition between dislocation transmission and dislocation source activation, a theoretical framework is established based on a dislocation pile-up model. It is found that both dislocation transmission and dislocation source activation exhibit strong dependence on the GB misorientation angle. The critical transmission stress derived based on an energy method also depends on the grain size in a scaling form similar to the Hall-Petch relation. The outgoing slip systems during dislocation transmission are successfully predicted and agree with experimental observations. Regarding the dislocation source activation, the critical activation stress is investigated by examining the local stress fields generated by single and multiple slip dislocation pile-ups. It is found that compared with single slip dislocation pile-up, the result of multiple slip dislocation pile-ups displays lower critical activation stresses and exhibits feature of sensitivity to loading direction, interpreting the reported results of dislocation source activation in polycrystals. Further comparison between dislocation transmission and dislocation source activation for ⟨100⟩ tilt GBs indicates that the dislocation transmission prevails at low angle GB, while dislocation source activation is prone to occur at high angle GB. Our theoretical studies quantify the dislocation-GB interaction induced by dislocation pile-ups, shed light on the competition between dislocation transmission and dislocation source activation, and might provide essential guidance for high-performance metallic material design.

RESEARCH STATUS OF DRY FRICTION BEHAVIOR OF METALLIC MATERIALS: A BRIEF REVIEW

Metallic materials are a class of well-developed engineering materials and have been extensively used in various engineering fields. Material removal that resulted from wear, mostly dry friction conditions, must be taken into consideration in the practical engineering application. Therefore, the tribological behavior of metallic materials and the process to improve their wear resistance under dry friction conditions are worth studying. This work begins with the research progress of the friction behavior of metallic materials in the sight of at room temperature and high temperature, as well as under the effect of magnetic field. Some surface modification technologies for improving the wear resistance of metallic materials under dry friction are also summarized.

Asymmetrical Rolling of Aluminum Alloys and Steels: A Review

Asymmetric rolling is an attractive metal forming process due to its simplicity, low cost and capability to produce unique characteristics in materials. The asymmetry promoted by the process leads to a formation of a large collection of texture components and a refined structure which is capable to improve the mechanical behavior of metallic materials. The aim of this work is to present a perspective of the process and to construct the bases for future development and application of this technique. Thus, several aspects are addressed such as process methods (i.e., dissimilarity of the rolls diameters, rolls angular speed or friction conditions), the process parameters (i.e., total thickness reduction, thickness reduction per pass, peripheral speed ratio, rolling routes) and their effect on material properties, including texture and microstructure evolution, and mechanical properties. This review is focused on the experimental description of asymmetric rolling applied to aluminum alloys and steels. Although the asymmetric rolling application was mostly at a laboratory scale, there is a good perspective for its implementation in the industry. The pros and cons based on the up to date literature and authors’ experience are presented and discussed.

A comparison of different crystal plasticity finite-element models on the simulation of nickel alloys

ABSTRACT Continuum crystal plasticity models based on the kinematics of plastic slip are widely developed and used in recent years to describe the anisotropic elasto-viscoplastic behaviour of metallic material. Various microstructural physical-based models have been proposed to reproduce experimental evolutions. This work aims to analyse and compare different crystal plasticity finite element models, especially those based on dislocation densities, from the simulations of stress–strain curves of a nickel base super alloy CMSX-4. Special attention is paid on hardening matrix. The adequacy between the simulated results and experimental data is commented, and it is found that a strain-rate- dependent double hardening matrix model can give a better prediction of the CMSX-4 behaviours.