Abstract

1. Introduction

2. Experimental

3. Results and discussion

4. Conclusion

Conflict of Interest

Supplementary Information

References

Abstract

     This study investigates the effect of graphene oxide (GO) on the mechanical and corrosion behavior, antibacterial performance, and cell response of Mg—Zn—Mn (MZM) nanocomposite. MZM/GO nanocomposites with different amounts of GO (i.e., 0.5wt%, 1.0wt%, and 1.5wt%) were fabricated by the semi-powder metallurgy method. The influence of GO on the MZM nanocomposite was analyzed through the hardness, compressive, corrosion, antibacterial, and cytotoxicity tests. The experimental results showed that, with the increase in the amount of GO (0.5wt% and 1.5wt%), the hardness value, compressive strength, and antibacterial performance of the MZM nanocomposite increased, whereas the cell viability and osteogenesis level decreased after the addition of 1.5wt% GO. Moreover, the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5wt% GO. In summary, MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.

Introduction

     Currently, because magnesium (Mg) alloys have more benefits than common metallic materials, ceramics, and biodegradable polymers, their biomedical applications have been increasing. In terms of mechanical features, metals have higher mechanical strength and fracture toughness than ceramics or polymers; thus, metals are more appropriate for load-bearing usages than ceramics or polymers [1–2]. The density of human cortical bone (1.75 g/cm3 ) is similar to the density of Mg (1.738 g/cm3 ) and Mg alloys (1.75–1.85 g/cm3 ) but lower than the density of biomedical titanium alloy Ti6Al4V (4.47 g/cm3 ) [3–4]. In terms of biocompatibility, certain amounts of Mg ions in the human body are connected with many metabolic reactions and biological mechanisms [5–6]. Mg alloys are suitable orthopedic and cardiovascular implants because further surgery to remove them is not needed [7–8]. However, an important drawback of Mgbased implants is that they do not have good resistance against corrosion in physiological environments [9]. Mechanical strength could be significantly reduced by rapid and uncontrollable corrosion processes, which leads to premature failure [10]. Moreover, the health of patients who have such implants could be at risk because of the evolution of hydrogen gas and alkalinization of the environments close to the interface between implant and tissue [11]. Therefore, to achieve the secure deployment of biomedical devices, the degradation/corrosion rate of Mg alloys needs to be controlled [12]. In this context, several methods, such as alloying, powder metallurgy (PM), and surface modification strategies, have been used in an extensive number of studies that aimed to solve the problem of corrosion in Mg alloys [13–14]. Among the best methods to enhance the corrosion resistance of porous Mg are PM processes, such as mechanical alloying [15–17].

Conclusion

     In this study, using the semi-powder metallurgy method, different contents of GO were embedded in the Mg–Zn–Mn (MZM) matrix to prepare MZM/xGO nanocomposites for orthopedic applications. The corrosion performance and the 24 20 16 12 8 4 0 0 −0.5 −1.0 −1.5 −2.0 Extension / mm MZM/GO Graphene oxide Graphene oxide Graphene oxide Graphene oxide Crack Crack (a) (c) 1.5GO 0.5GO 1GO MZM (b) MZM composite MZM/0.5GO MZM/1GO MZM/1.5GO 49 59 63 64 Compression strength / N 4820 17810 19960 9620 1.12 1.31 1.44 0.72 Force / (10 3 N) Micro hardness, HV Extension / mm Material nanocomposite Fig. 10.    (a) Typical compressive curves and (b) hardness and compressive strength values of the MZM/xGO nanocomposites; (c) schematic diagram of the crack deflection toughening mechanisms of GO in the MZM/xGO nanocomposites. S. Jabbarzare et al., Effect of graphene oxide on the corrosion, mechanical and biological properties of Mg-based … 317 mechanical and biological characteristics of the MZM/xGO nanocomposites were analyzed. The microstructural assessment showed that a uniform distribution was achieved in the MZM/0.5GO and MZM/1GO nanocomposite specimens. However, agglomeration was observed in the MZM/1.5GO nanocomposite specimen. The results showed that the GO content, hardness value, and compressive strength are positively associated. In this context, the MZM/1GO nanocomposite has higher hardness value and compressive strength than the Mg-based nanocomposite without GO. The MZM/ 0.5GO nanocomposite exhibited a nearly comparable corrosion resistance to the MZM/1GO nanocomposite, even though the incorporation of more GO has an unfavorable effect on the Rct value of the MZM matrix. The MTT assay results showed that the MZM/1GO nanocomposite increased the MG63 cell viability and ALP activity, indicating the increasing level of osteogenesis. The results of the analysis of antibacterial activity showed that the MZM/1.5GO nanocomposite had a noticeable effect on antibacterial effectiveness toward bacteria, including Salmonella–Shigella and Klebsiella pneumoniae. In summary, the results indicate the possibility of utilizing the MZM/1GO nanocomposite for implant applications with effective anti-infection characteristics.

1- Introduction

2- Experimental method

3- Results and discussion

4- Conclusions

References

Abstract

The deuterium permeation behavior of palladium-coated 316L stainless steel and 430 stainless steel was studied by the gas permeability testing device in this study. The results show that the deuterium permeability of the palladium-coated 316L stainless steel tested at 350 °C∼650 °C was very close to the Forcey’s results. This way, the conformity to some other reported results has been verified for the gas permeability testing device. The deuterium permeability for the oxidized 430 stainless steel was compared with that for the palladium-coated 430 stainless steel at temperature range of 350 °C–600 °C. The deuterium permeability for the oxidized 430 stainless steel was reduced by one order of magnitude compared with that for the palladium-coated 430 stainless steel. However, the activation energy of deuterium permeation as gas form for the oxidized 430 stainless steel was almost the same as that for unoxidized 430 stainless steel.

Introduction

Zirconium hydride is used as the reactor moderator in the thermionic space nuclear power and it easily decomposes hydrogen in the operating environment. The released hydrogen penetrates into the core through the relevant structural components, affecting the physical parameters of the reactor [1]. Compared with 316L austenitic stainless steel, 430 ferritic stainless steel has the advantages of good thermal conductivity, low thermal expansion coefficient and low sensitivity to stress corrosion cracking. It is selected as one of the alternative reactor core materials for structural components of the thermionic space nuclear power. Therefore, investigating the hydrogen permeation behavior of 430 ferritic stainless steel has important engineering application value for the development of thermionic space nuclear power. A lot of research has been carried out on the preparation and properties evaluation of hydrogen isotope permeation barrier coatings for the fusion reactor. However, 316L stainless steel or low-activity ferritic/martensitic steel was used as the substrate material in most of these studies [2–15]. There are few reports on the hydrogen isotope permeation behavior of 430 ferritic stainless steel. In the present study, the deuterium permeability of palladium-plated 316L stainless steel was first tested and compared with the reported values to verify the conformity to other reported results for the gas permeability testing device. Then the deuterium permeation behavior of the palladium-plated 430 stainless steel as well as that with natural oxide film was investigated.

1- Introduction

2- Thermodynamic calculation on solidification path and segregation behavior

3- Modeling of the eutectic fraction

4- Experimental procedure

5- Results and discussions

6- Conclusion

References

Abstract

The effect of cooling rate on the microstructure and TiC precipitation of TiC-reinforced wear-resistant steel was investigated by different casting techniques. Thermodynamic and solute segregation modeling was performed to determine the evolution of TiC fraction in wear-resistant steel after rapid solidification. The evolution of TiC fraction due to solute segregation within the framework of Clyne–Kurz (C-K) model was examined. The model prediction is consistent with the experimental results.

Introduction

As transition metal carbide, TiC is characterized by its excellent properties such as very high melting point and hardness [1,2]. These properties have led to their wide applications as important precipitates for strengthening steels [3,4]. The volume fraction, particle size and distribution of the reinforcing phase are significant for improving the mechanical properties [5,6]. To obtain the desired wear resistant properties and mechanical strength of steels, it is important to control the volume fraction of TiC [7]. As it is known, the inevitable solute segregation occurred in non-equilibrium solidification process enriches the solute in liquid, and influence the amount of eutectic and other phases [8]. Quantitative prediction of microsegregation is complicated by the difficulties in accounting for eutectic and secondary phase formation in steel. Within the past decades, correspondingly various analytical models were developed to predict solute redistribution and related phenomena [9-14]. Among these microsegregation models, the Clyne–Kurz model is considered to be the most popular one. However, previous works have the disadvantage that a constant partition coefficient must be assumed.

1. Introduction

2. Test specimens

3. Methods for corrosion tests

4. Test results on the chemical properties of corroded specimens

5. Test results on the mechanical properties of corroded specimens

6. Concluding remarks

Declaration of Competing Interest

Acknowledgements

References

Abstract

The objective of the paper was to experimentally examine the effects of corrosion wear on the chemical and mechanical properties of structural steels. Naturally-progressed corrosion testing on structural steel specimens was conducted during a period of 12 months. Three types of structural steels were tested: mild steel (grade A), AH32 steel, and DH32 steel. Different conditions of the corrosive environment were applied with three dry or water-immersed conditions, namely air (dry), freshwater immersion and seawater immersion, and with three temperatures, namely room temperature (18 °C), 0 °C, and −10 °C. The chemical and mechanical properties of structural steels were measured before and after the corrosion testing. Based on the test results, the characteristics of corrosion progression rate for structural steels were studied and reported in a separate paper [21, doi: https://doi.org//10.1080/17445302.2019.1664128]. It is concluded that corrosion does not affect the chemical and mechanical properties of structural steels. Details of the test database were documented.

Introduction

Steel is a common material used for the construction of naval, offshore, mechanical, and civil engineering structures. As steel structures get older, their safety and integrity can suffer from corrosion wear which is affected by various parameters of influence in the corrosive environment, including oxygen content, salinity, pH value of water, temperature, atmospheric pressure, suspended solids, velocity of water waves, together with various physical and chemical factors of material [1–5]. Land-based steel structures may be exposed to the immersion of freshwaters or related humidity while the surfaces of steel ship and offshore structures at sea are usually touched on seawaters [6]. In winter season or Arctic area, the operational temperature of such structures is in sub-zero temperatures (or lower than the room temperature).

To evaluate the structural integrity with corrosion damage at the level of steel structural members or entire structures, it is essential to identify the chemical and mechanical properties of corroded structural steels, i.e., at the level of materials. It is generally considered that corrosion does not affect the chemical and mechanical properties of structural steels [3], but obvious evidences or test database are lacking in the literature and thus some studies attempted to derive computational models that the corrosion wear was dealt with as a parameter of influence on the mechanical properties of structural steels [7–11]. The objective of this paper was to obtain the physical test database to investigate the effects of corrosion wear on the chemical and mechanical properties of structural steels, and ultimately to contribute to the prevention of such an unnecessary confusion on the issue.

1. Introduction

2. Significance of the research

3. Materials and experimental procedure

4. Results and discussion

5. Conclusions

Declaration of competing interest

Acknowledgements

References

Abstract

Alkali-activated concretes are being considered as an alternative environmentally friendly construction materials compared to the ordinary Portland cement. However, although these materials have reported mechanical properties comparable to those of OPC, the corrosion of reinforcing bars is a major durability issue that needs to be studied. This article studies the corrosion performance of an alkali-activated binary reinforced concrete (AABC) based on natural volcanic pozzolan (NP) and ground blast furnace slag (GBFS) exposed to chlorides ions. OPC concrete was used as reference material. To carry out the study, accelerated chloride ingress methods (impressed voltage, wet-dry cycles, and saltwater immersion (3.5% NaCl)) were used. Monitoring of the corrosive process was carried out using the techniques of half-cell potential, linear polarization resistance, polarization curves and curves of current intensity versus time. As complementary techniques, surface electrical resistivity and resistance to chloride ion penetration were evaluated. AABC showed higher resistance to chloride ion penetration compared to OPC concrete, a reduction of the charge passed up to 60% at 360 days of exposition. In general, the various accelerated chloride ingress techniques employed in the present research revealed that reinforcing steel embedded in AABCs have a higher resistance to corrosion compared to steel bars embedded in Portland cement (OPC)-based concrete. It should be noted that the B constant values obtained for AABC differ from the values commonly used in (OPC)-based concretes. In addition, the results indicate that the ranges of corrosion probability, such as half-cell potentials or corrosion currents, specified for OPC concretes should be checked for its application in alkali-activated concretes.

Introduction

Reinforced concrete based on ordinary Portland cement (OPC) is one of the most widely used materials in the civil industry due to its versatility, properties and low cost. One of the most important factors for the construction industry is the durability, which is determined by the useful life of the material under real service conditions, including its exposure to aggressive environments [1]. Durability is not an intrinsic property of a material, since it depends on the conditions of service, so that in concrete it is known to vary according to the type of environment to which it is exposed. One of the biggest threats that reinforced concrete faces is the corrosion of reinforcing steel due to cracking, delamination, and in severe cases, the partial or total collapse of a structure. The primary cause is the exposition to aggressive environments such as CO2 and/or the entry of chloride (Cl−) ions [[2], [3], [4], [5]]. These agents have been responsible for most structural damage and, therefore, a significant increase in investment in structure maintenance and repair. Chloride ions can come from a range of sources – marine environments, the use of de-icing salts (≈NaCl), chemical substances coming into contact with the concrete, or they may be present in the concrete mix, as happens with the inclusion of some types of additives (CaCl2) during production. Chlorides diffuse through the concrete and, on reaching a critical concentration near the steel, cause destruction of the passive layer and initiate the corrosive process, generating pitting corrosion in the steel [6,7]. In addition to concrete durability, a major concern is the environmental impact associated with production, especially relating to the use of Portland cement (OPC). Indeed, the OPC industry generates annually 2 billion tons of CO2, corresponding to 8–10% of greenhouse gas emissions into the atmosphere [[8], [9], [10]]. For this reason, research applied to the development of alternative low carbon footprint cementitious materials is a priority for the construction sector [11]. Among these alternatives, alkali-activated materials (AAMs) have caught attention. These are obtained from chemical interaction between an alumina-silicate material (precursor) and a strongly alkaline solution (activator) [[12], [13], [14]]. AAMs are synthesized at temperatures between 25 and 100 °C, while OPC production temperatures rise to 1460 °C to obtain clinker. AAMs can thus be considered as potential low carbon cements [15]. These types of materials also have structural mechanical strengths and physical characteristics such as reduced permeability and thermal stability [16,17].

1- Introduction

2- Materials and Methods

3- Results and Discussion

4- Summary of Passive Behaviour

5- Conclusions

References

Abstract

The corrosion behaviour of type 316L stainless steel in aqueous 30–50 wt%. NaOH at temperatures up to 90 °C has been elucidated. Exposure to room temperature environment showed parabolic weight loss behaviour, with corrosion rates of up to 0.4 mm/year. Higher NaOH concentrations and exposure temperatures resulted in a reduced stability of the electrochemical passivity domain, associated with higher corrosion rates. Exposure to de-aerated 50 wt%. NaOH presented corrosion rates of up to 0.5 mm/year at open circuit potential, with maximum corrosion rates under polarisation of up to ≈ 18 mm/year. The formation of a dark iron-oxy-hydroxide and nickel-oxide was observed, with exposure to temperatures in excess of 50 °C. The behaviour of type 316L stainless steel in hot caustic environment is compared to types 204, 304, 2205 stainless steel, and nickel alloy 200.

Introduction

The corrosion of stainless steel in hot caustic environment has been the subject of a number of investigations, typically with a focus on Kraft pulping liquors [1–11]. The material performance in these environments is governed by the stability of the passive surface flm, which develops as a function of alloy microstructure, chemical composition, and associated environmental interactions. Austenitic stainless steels generally show high corrosion rates when exposed to concentrated, deaerated alkaline aqueous environment at temperatures above 60 °C, with typical corrosion rates of 0.05–2 mm/year. Very dilute caustic solutions show reduced corrosion susceptibility, for example, with exposure to mildly caustic environment up to pH 12, resulting in corrosion rates of 0.01 mm/year [12–14]. The latter investigation also concluded that temperature is key for understanding material behaviour in these environments, directly afecting corrosion rates of stainless steel in NaOH containing environment [6, 7]. In NaOH environment at room temperature, rates as low as a few μm/year have been reported [6, 15–22]. Based on the Pourbaix diagrams of Iron, Chromium and Nickel, the possibility of forming a passive flm with exposure to caustic pH supports the argument of using stainless steel in these media. A summary of the corrosion behaviour of stainless steels with exposure to diferent caustic environments is provided in [12]. The aim of this paper is to provide a comprehensive overview of the corrosion performance of type 316L in hot caustic aqueous environments. The project was centered on identifying alloy composition and environment-related parameters, including temperature, de-aeration, and NaOH concentration, to better understand the passivation behavior of stainless steels microstructure.

INTRODUCTION

EXPERIMENTAL

RESULTS AND DISCUSSION

KINETIC STUDIES

CONCLUSIONS

REFERENCES

Abstract

The present paper aims to compare the corrosion protection performance of electrodeposited Ni‒P with Ni–P–C nanocomposite coatings in 3.5 wt % NaCl solution in order to assess the influence of carbon nanoparticles on corrosion behavior of these coatings, by the potentiodynamic polarisation Tafel curves and electrochemical impedance spectroscopic (EIS) techniques. The effect of heat treatment on the coatings performance was also studied. The results revealed that heat treated Ni–P–C nanocomposite coating in air at 673 K significantly improved resistance to corrosion compared with Ni–P coatings. This behavior was related to incorporation of carbon nanoparticles into Ni–P matrix using in-situ electrochemical reduction of L-lysine, which shift the corrosion potential (Ecorr) positively, also the corrosion current density (Icorr) and the double layer capacitance (Cdl) values decrease, the charge transfer resistance (Rct) and efficiencies of inhibition (IE, %) increase, indicating improvement in the corrosion resistance in seawater environment. Microstructure, phase change and chemical composition of the prepared coatings were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD) and elemental microanalysis (EDX), respectively.

INTRODUCTION

Electrodeposited composite coatings based on a Ni–P alloy matrix containing different fine particles of nonmetallic, ceramic or polymer compounds [1‒10] have attracted attention in many industrial fields due to their good mechanical, chemical and electrocatalytic properties including enhanced wear resistance combined with a good corrosion resistance and especially high electrocatalytic activity for hydrogen evolution reaction (HER) in chlor-alkali industries and water electrolysis [11–17], when compared to pure nickel coatings. Ni–P coating with phosphorus content over 9 wt % are considered amorphous and possesses excellent mechanical properties such as corrosion resistance [18, 19]. This protective film can be deposited by electroplating and electroless plating onto a metallic or nonmetallic substrate to prevent attack by hostile environments [20].

1- Introduction

2- Mechanism

3- Corrosion inhibitor chemistry

4- Conclusions and prospects

References

Abstract

Corrosion of metals has been a widespread issue in industries for centuries. The use of corrosion inhibitors in rust preventative fluids are commonly employed to provide the temporary corrosion protection to metals. The aim of this review is to summarize the rust inhibition properties, inhibition mechanism, chemistry and development of corrosion inhibitors for rust preventative fluids. Some suggestions for further research on corrosion inhibitors have also been discussed.

Introduction

Corrosion is the degradation of a material’s properties by chemical and/or electrochemical reaction with the environment, and in most cases it means the electrochemical oxidation of metal. The study of National Association of Corrosion Engineers (NACE) estimated that the global cost of corrosion to be $ 2.5 trillion annually, equivalent to about 3.4% of the global Gross Domestic Product (GDP) [1]. It also found that implementing corrosion prevention best practices can save 15–35% of the cost of damage, that is $ 375–875 billion. Among the various methods available to prevent corrosion of metals, rust preventative fluids are extensively used to provide temporary corrosion protection during manufacturing processes, storage and shipment. Rust preventative fluids are prepared by mixing corrosion inhibitors, film-forming agents and other additives into a base fluid, and it can be classified as solvent-based, oil-based and water-based rust preventatives according to the types of base fluid [2]. It is definite that corrosion inhibitors are critical for them to achieving high performance. Inorganic and organic inhibitors are the two main types of corrosion inhibitors. Inorganic inhibitors, such as nitrite, nitrate, chromate, dichromate, phosphate, are widely used in different base fluids and for various metals [3]. On the other hand, organic inhibitors are the compounds containing one or more polar groups (with O, N, P, S atoms, and π electrons), which are effective to prevent corrosion via adsorption on the metal surface [4–6]. Since the polar groups are usually regarded as the reaction centers for the adsorption process, the strength of adsorption is strongly dependent on the electron density and polarizability of the polar groups [7]. Accordingly, organic inhibitors include sulfonates, alcohols, ethers, amines, amides, amine salts, carboxylates, heterocyclic nitrogen compounds, phosphates, polymers, natural products, and others in consideration of polar groups nature. The present article reviews the mechanism and development of corrosion inhibitors for rust preventative fluids.

1- Introduction

2- Criteria for crack initiation and propagation

3- A model for the crack density evolution

4- Analysis of the delamination onset and propagation

5- Conclusions

References

Abstract

A damage-based design procedure has been developed by the authors to predict the damage evolution and the stiffness degradation in polymeric composite laminates under fatigue loading. For a safe and reliable design against fatigue degradation and failure, the initiation of the main damage mechanisms (off-axis cracks, delamination and fiber failure) as well as their evolution are considered and suitable models are proposed for the quantitative assessment of the lifetime associated to each mechanism. In parallel, the stiffness degradation deriving from the damage evolution over the fatigue life is properly described. After the illustration of the overall damage-based strategy, the paper discusses in details the analysis and modelling of the off-axis crack initiation and propagation. The initiation of cracks in the off axis plies has been proved to be the consequence of a damage process occurring at the microscopic scale since the early stages of fatigue. On this basis, crack initiation prediction is based on the use of local stress parameters: Local Hydrostatic Stress, LHS, and Local Maximum Principal Stress, LMPS, depending on the local degree of multiaxiality of the stress state and accounting for the statistical distribution of the local laminate strength. The propagation phase is then quantified by using a conventional fracture mechanics approach. The model has been implemented in a Matlab procedure for the quantitative evaluation of the crack density in each ply of a laminate during its entire fatigue life. The knowledge of the crack density trend allows the description of the laminate stiffness evolution taking advantage of another model recently developed by the authors, valid for a generic laminate configuration and accounting for the interaction between cracks in the neighbouring plies.

Introduction

Composite materials are excellent candidates for the development of reliable lightweight components and structures complying, for instance, with the needs of decreasing fuel consumptions in the transportations field or increasing the specific energy production in the wind energy field. Most of structural components manufactured with composite materials are subjected during their in-service life to cyclic loadings, which might lead to a progressive damage, a consequent loss of stiffness and residual strength and, eventually, to the final failure. The “design against fatigue” is therefore fundamental to improve the reliability of composite structural parts. To meet the demand of fatigue design tools for composite structures, the Composite Group at DTG-University of Padova is working since several years to the development of a design framework suitable to predict the initiation of damage, its evolution and the final failure of composites under cyclic loadings [1-11]. As a starting point of the discussion, it is important to clarify the concept of “design against fatigue”, which can be meant in different ways depending on the requirements of the part under design: i) design against crack initiation (no damage); ii) design against stiffness degradation (damage tolerant design); iii) design against final failure. In applications like fuel and pressure vessels, fuel rails or other, the onset of damage has to be avoided to satisfy the safety requirements. In this case, the capability to predict the life spent for the initiation of the first crack is essential. In other cases like automotive composite frames, turbine blades, bicycle cranks or composite rims, the global stiffness can be the design driver. Due to the several fatigue damage mechanisms, structural composite components can lose up to 30-40% of their initial stiffness (depending on lay-up and load conditions) much before the final failure. Therefore, for a more reliable and cost-effective design, it is important in these cases to estimate the stiffness degradation under the specific loading conditions [6]. When only the load bearing capability of the part is of interest, the final failure (separation into two or more pieces) is the design target.

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION

REFERENCES

INTRODUCTION

Magnetic films are widely used in various electric devices and many fabrication processes, such as sputter depositions, vapor depositions, ion plating, and electroplating. To apply the films to commercial applications, a high deposition rate of the process is an important parameter, and some methods, e.g., pulsed laser deposition, aerosol deposition and arc plasma deposition are well known as high-speed deposition processes. Owing to high economic viabilities and high deposition rates, electroplating is one of the more effective methods to obtain magnetic films. Many studies on electroplated magnetic films have been carried out, and superior soft magnetic properties have been reported. Typical electroplating processes for soft magnetic films employ distilled water as the solvent for electroplating baths. Although aqueous solutions are suitable plating baths, it is difficult to deposit some metals due to decomposition of the water during the plating. Therefore, we recently introduced deep eutectic solvents (DES) for electroplating since many productive advantages of DES have been reported. In our previous studies on soft magnetic films for DES-based plating baths, we found that the textures of electroplated Fe-Ni films dramatically changed depending on the Fe content in the film, confirming the high current efficiency of the plating process (> 90%). Since the current efficiency and the current density during the electroplating are particularly important parameters to obtain a high deposition rate, the obtained high current efficiency for the DES-based baths is attractive for realizing a high deposition rate. In the present study, we focused on another parameter of current density to enhance the deposition rate and investigated the effect of current density on the plating rate, the surface morphology and the magnetic properties of the Fe films.

This paper is concerned with the behaviour of composite beams made from stainless steel. Steel-concrete composite members are widely used in the design and construction of modern structures such as bridges and high rise buildings. Depending on the degree of composite action, a significant increase in strength and stiffness performance is gained compared to a bare steel or concrete section. This results in savings not only in construction depth but also in terms of material consumption, which means also lower environmental impact and reduced energy consumption [1]. Composite beams which are subjected to positive bending (i.e. sagging) offer a particularly efficient use of the constituent materials. In this case, the steel section is subjected to tensile stresses whilst the concrete slab acts primarily in compression, thus utilising the favourable characteristics of each material. It is generally desirable for plastic design that composite beams have a ductile cross-section, in which strain hardening develops in the lower flange before the collapse moment is reached [2]. However, for calculating the load-bearing capacity of composite beams, design codes such as Eurocode 4 [3] generally neglect strain hardening effects and employ a rigid-plastic analysis of the cross-section, thus providing conservative predictions of the capacity in many cases, particularly when ductile materials such as stainless steel are employed. Stainless steel has been employed in construction since the 1920s, when the main usage was in building facades. Nowadays, stainless steel has become popular in a wide range of construction and load-bearing applications due to its excellent mechanical properties such as higher strength and ductility, better retention of strength and stiffness at high temperature [4] and excellent corrosion resistance properties, compared with carbon steel. Stainless steel does not require coatings to be applied, thus leading to life-cycle cost savings relative to carbon steel especially for offshore steel structures [5], as well as reducing maintenance and rehabilitation costs. In recent years, stainless steel has been the subject of intensive research in order to provide useful, efficient and reliable design guidance for engineers. The vast majority of research into stainless steel has been focussed on bare steel elements. Researchers have investigated the flexural behaviour of stainless steel columns subjected to compressive loading or combined compression and bending moment (e.g. [6–9]) and beams (e.g. [10–13]) as well as beams and columns under fire conditions (e.g. [14]). The use of stainless steel in composite structures has hitherto received little attention from the engineering community and research studies have generally been limited to investigating the behaviour of concrete-filled stainless steel columns under different loading conditions using experimental and numerical analysis. Lam et al. [15] conducted experiments on the behaviour of axially loaded concrete-filled stainless steel elliptical sections made from normal and high strength concrete. Uy et al. [16] carried out experiments on concrete-filled stainless steel circular, square and rectangular sections of short and slender columns subjected to combined axial compression and bending moment. The behaviour of concrete-filled stainless steel circular and square tubular sections subjected to axial compression under fire conditions has also been studied through a series of experiments [17]. Moreover, nonlinear finite-element analysis was used to investigate the performance of concrete-filled stainless steel tubular columns of square, L-, T-, and + shape sections under axial compression or combined compression and bending moment [18, 19]. To date, there has been no research available in the public domain on traditional composite beams (i.e. a bare steel section connected to a concrete slab through shear connectors) using stainless steel. The following section describes the context in which these members are highly relevant in the current era.

مقاله سال 2017

هدف مقاله حاضر تشخیص اثرات موقعیتهای نمونه گیری و بارگذاری موجی شکل بر روی خستگی کم چرخه درجه بالا (HTLCF) و عمر خستگی-خزشی یک سوپر آلیاژ GH4169 پایه نیکل سختکاری رسوبی شده، است. هر دو مکانیسم شکست و تغییر شکل در اینجا در نظر گرفته است. مشخص شد که HTLCF و عمر خزشی-خستگی نمونه ها بوسیله زیرساختارهای ناهمگن در موقیتهای مختلف تحت تاثیر قرار گرفته است. در مقایسه با آزمایشهای HTLCF، حضور زمانهای ساکن در آزمایشهای خزشی-خستگی، تمایل به کاهش تعداد چرخه های شکست را دارد. آسیب بین دانه ای در هر دو مرحله شروع و انتشار ترک خوردگی مشاهده شد. برای بارهای ساکن تحت تنش، آسیب بین دانه ای بطور عمده با حفره های دستیار-رسوب همراه است. با این حال اکسیداسیون برای حضور آسیب بین دانه ای برای بارهای ساکن تحت فشار، در نظر گرفته میشود.