Advanced Structural Materials Research Articles

ASSESSMENT OF COMFORT OF THE URBAN ENVIRONMENT (ON THE EXAMPLE OF THE CITY OF IZHEVSK)

The availability of housing is one of the most important basic human needs. The development of construction technologies, the emergence of more advanced structural materials and building mechanisms have significantly accelerated the process of building construction. The developed system of mortgage lending stimulates the growth of the purchasing power of the population. The problem of housing shortages is gradually weakening and replaced by the problem of excess housing supply over demand for it. In the new conditions, the potential buyer of the apartment is not only interested in its size and price, but also in the environment surrounding the selected house, its comfort. The need to assess the comfort of the urban environment in Russia has been discussed in the last 5-6 years. Comfort is the optimal state for a person of the surrounding social, economic, natural, infrastructural environment, ensuring the health and performance of individuals or their communities. Its level is estimated by a whole group of multidimensional, multidirectional indicators, some of which do not have a quantitative form. It is necessary to use an aggregated, integral, that is, a composite indicator for their successful sharing. Integrated indicators of urban comfort have significant drawbacks, applied in practice. The authors of the article proposed to apply a modified formula for calculating comfort, proven by practice. The authors used the developed indicator to assess the comfort of the urban environment in 247 Izhevsk new buildings. The results obtained showed the effectiveness of the methodology and the possibility of using the indicator in the practical activities of the developers of the city.

Microstructural Modifications of Dual‐Phase Steels: An Overview of Recent Progress and Challenges

Optimization of the microstructure and its effect on the strength and ductility of the steel is one of the main aspects of the researcher's effort toward production of advanced structural materials. There have been various investigations focusing on the thermomechanical treatment and grain refinement of steel while some researches are dealing with the modification of chemical composition. This article considering major parameters influencing the mechanical properties of steels aims to present an overview of the outstanding achievements in improvement of the dual‐phase steels. Following the obtained consensus, some advanced promising microstructural modification strategies are also suggested, which can bring new insights to shed light upon the further enhancement of the mechanical behavior of the dual‐phase steels.

Mechanical behavior of composite ship structures with open-hole

Composite materials, as advanced structural and functional materials, are increasingly used in naval and civilian fields. There are different structures with open-hole in the ship hull. The open-hole damages the continuity of the composite structure and has a direct impact on the strength and stability of the composite structure. Therefore, it is of great significance to study the mechanical behavior of composite ship structures with open-hole to ensure the safety of the ship. Based on the numerical method, the mechanical behavior of the typical composite ship structures with open-hole was investigated, and the critical buckling load, buckling mode, post-buckling behavior, ultimate bearing capacity and stress concentration of the composite structures with open-hole were analyzed. The Hashin failure criterion and complete unloading failure model were used to analyze the nonlinear buckling behavior of different composite structures with open-hole. The results show that the ultimate bearing capacity of the composite structures with typical open-holes such as rectangle, rhombus, ellipse and circle is more than 2 times of its critical buckling load, this proves that the composite structures with open-hole can have a certain bearing capacity after initial buckling. Compared with the same scale structure without open-hole, the critical buckling load and ultimate bearing capacity are reduced by about 10% and 50%, respectively. The influence of various open-holes and layer thickness on the mechanical behavior of composite ship structures is estimated through the parametric study, which provides an effective reference for the design optimization and performance evaluation of composite ships.

Cavitation erosion-corrosion resilient surfaces through reciprocating friction processing

Here, an excellent cavitation erosion-corrosion resistance of stainless steel using a novel severe surface deformation technique, reciprocating friction processing (RFP) was demonstrated. The RFP treated stainless steel showed nano-grained, nano-twinned microstructure along with high dislocation density. The RFP treated steel significantly surpassed the performance of advanced structural materials including high entropy alloy (Al0.1CoCrFeNi) and complex concentrated alloy (SiC reinforced Al0.1CoCrFeNi), demonstrating the lowest cavitation erosion and cavitation erosion-corrosion rates for this class of materials. The RFP treated steel demonstrated outstanding corrosion behavior in 3.5% NaCl solution as well. The unusual performance of RFP treated steel is attributed to its excellent mechanical strength and strong passivating behavior.

Stable microstructure in a nanocrystalline copper\u2013tantalum alloy during shock loading

The microstructures of materials typically undergo significant changes during shock loading, causing failure when higher shock pressures are reached. However, preservation of microstructural and mechanical integrity during shock loading are essential in situations such as space travel, nuclear energy, protection systems, extreme geological events, and transportation. Here, we report ex situ shock behavior of a chemically optimized and microstructurally stable, bulk nanocrystalline copper–tantalum alloy that shows a relatively unchanged microstructure or properties when shock compressed up to 15 GPa. The absence of shock-hardening indicates that the grains and grain boundaries that make up the stabilized nanocrystalline microstructure act as stable sinks, thereby annihilating deformation-induced defects during shock loading. This study helps to advance the possibility of developing advanced structural materials for extreme applications where shock loading occurs.

Theory of designing the gradient microstructured metals for overcoming strength-ductility trade-off

Gradient microstructure design has been found to be an effective approach to significantly produce the utmost advanced structural metallic materials, which have a signature in mechanical characteristic of strength-ductility-hardenability combination. In this work, a physical theory and mechanism-based numerical model are developed for sophisticatedly designing the gradient microstructured metals. It considers the gradient distribution of grain size, twin, martensite and austenite in a metallic alloy. The numerical results are validated through experiments. The mechanical performance of high strength, large ductility and considerable hardenability is achieved and their trade-off is successfully overcome.

Recent advances in carbon nanotube-geopolymer composite

Benefiting from the superior engineering properties and reduced environmental footprints, geopolymer is being considered as an alternative to Portland cement for construction applications. The incorporation of carbon nanotube into geopolymer matrix contributes to improve the mechanical and electrical behaviours of resultant composites. Moreover, the obtained carbon nanotube-geopolymer composite possesses functionalities needed for future, i.e. improved safety and sustainability composed with smart features like self-condition monitoring. This kind of innovative and promising composite is attracting increasing attention from scientific and engineering fields. This work reviews the state-of-the-art progresses in the fabrication and characterization of carbon nanotube-geopolymer composites, including dispersion technologies of carbon nanotube, functional characteristics and smart features of resultant composites, and corresponding reinforcement mechanisms. Discussions on current research limits and potential opportunities are made to promote the investigation and application of carbon nanotube-geopolymer composite as advanced structural material.

Synergistic strengthening effect of in-situ synthesized WC1-x nanoparticles and graphene nanosheets in copper matrix composites

In metal matrix composites, it is commonly a hard task to achieve synergistic strengthening and toughening effects between two-dimensional graphene and zero-dimensional nanoparticles (NPs) reinforcements due to their huge dimensional gap. Herein, we developed an in-situ solid-state reaction method to incorporate graphene nanosheets (GNSs) and WC1-x NPs into copper matrix. It was proved for the first time by thermodynamics and crystallography calculations that the unusual γ-WC1-x phase can be generated from the solid reaction and maintain stable at room temperature. Thanks to the unique distribution types of WC1-x, i.e. intergranular or intragranular distribution while other parts anchored on the surface of the GNSs, Orowan strengthening and load transfer strengthening were simultaneously achieved in the composites. Meanwhile, the thermal conductivity was also measured to be equal to that of pure Cu, exhibiting a promising prospect in applications as advanced multifunctional structural materials.

Dissimilar-metal bonding of a carbide-dispersion strengthened vanadium alloy for V/Li fusion blanket application

Carbide-dispersion strengthened (CDS) vanadium alloy is a kind of advanced structural material for V/Li fusion blanket. The welding technology for the alloy is very important for its application in fusion reactors. In the present study, preliminary investigation on dissimilar-metal bonding by hot isostatic pressing (HIP) was carried out for the CDS V alloy by joining with the conventional V–4Cr–4Ti alloy. Microstructural characterization for the bonding interfaces and mechanical tests for bonding property evaluation were analyzed for the HIP joint. The results show that after the HIP, the grain size of the V–4Cr–4Ti base metal (BM) obviously increases, while the grain size near the interface is much smaller than that in the V–4Cr–4Ti BM. This is the reason why the hardness near the interface is larger than that of the V–4Cr–4Ti BM. By shear test evaluation, the HIP joint possesses good bonding property with sound strength and ductility. Because there is no phase transformation during HIP, no post-bond heat treatment (PBHT) is necessary for the dissimilar-metal joint.

Active corrosion protection of super-hydrophobic corrosion inhibitor intercalated Mg–Al layered double hydroxide coating on AZ31 magnesium alloy

Magnesium alloys, the advanced lightweight structural materials, have been successfully applied in the manufacturing field. Unfortunately, their poor corrosion resistance restrains the potential wide applications. In this work, anti-corrosion coatings were fabricated via the in-situ growth of the corrosion inhibitors intercalated magnesium-aluminum layered double hydroxide (Mg–Al LDH) on AZ31 magnesium alloy and then post-sealing it by a super-hydrophobic coating. SEM, XRD, EDS, FTIR, XPS and contact angle test were conducted to analyze physical/chemical features of these coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy were recorded to assess the anti-corrosion performance of prepared coatings. Surprisingly, Mg–Al LDH with molybdate intercalation and lauric acid modification achieves the excellent corrosion inhibition performance (99.99%) due to the multicomponent synergistic effect such as the physical protection of Mg–Al LDH, the corrosion inhibition of molybdate and super-hydrophobic properties of lauric acid. This work presents a scientific perspective and novel design philosophy to fabricate the efficient anti-corrosion coating to protect magnesium alloys and then expand their potential applications in other field.

Zr segregation in Ni–Zr alloy: implication on deformation mechanism during shear loading and bending creep

Grain boundary (GB) migration and grain growth in nanocrystalline metals are major obstructions to exploit these materials to their fullest potential, thus limiting their utility as advanced structural materials. Here, we investigate the effect of Zr segregation to a Ni GB on migration and subsequent strengthening during shear deformation and high-temperature bending creep. Specifically, using molecular dynamics simulation, we simulate deformation of a Ni bicrystal specimen having a symmetric ∑5 grain boundary with and without segregated Zr. It is found that GB segregation up to 0.4 at.% pins the CSL boundary resulting in increased shear strength. Similar behavior is also observed in the case of bending creep deformation where the creep resistance increases only up to 0.4 at.%. This study indicates that larger amounts of GB segregation cause destabilization of the local atomic structure and consequently affect the GB stiffness. Moreover, we investigate the effect of Zr segregation on the interaction between the GB and a dislocation. We find that the preexisting dislocation is absorbed in the GB region for both clean and segregated specimens; however, the absorption path of the dislocation is different due to the change in GB stiffness caused by the Zr segregation.

A gradient dislocation-structured low-carbon steel with enhanced strength-ductility synergy

Usually, the improvement of strength of structural materials is at the cost of ductility. Here, a superior synergy of high strength (σy ~ 526.8–582.6 MPa) and ductility (εf ~ 25.5–19.3%) is achieved in the gradient dislocation-structured low-carbon steel subjected to torsion deformation, which is much better than that (σy ~ 317.9 MPa and εf ~ 22.8%) of its coarse-grained counterpart. The enhanced strength is attributed to the back stress, grain refinement and the introduction of numerous dislocations (i.e., work hardening) whose density increases consistently with the radius along from the core to the surface. The high ductility results from the promising work hardening capacity of the gradient dislocation-structure. This study provides a practical route to developing advanced structural materials with enhanced integrated mechanical properties.

Enhanced Biocorrosion Resistance and Cellular Response of a Dual-Phase High Entropy Alloy through Reduced Elemental Heterogeneity.

The leaching out of toxic elements from metallic bioimplants has serious repercussions, including allergies, peripheral neuritis, cancer, and Alzheimer's disease, leading to revision or replacement surgeries. The development of advanced structural materials with excellent biocompatibility and superior corrosion resistance in the physiological environment holds great significance. High entropy alloys (HEAs) with a huge compositional design space and outstanding mechanical and functional properties can be promising for bioimplant applications. However, microstructural heterogeneity arising from elemental segregation in these multiprinciple alloy systems is the Achilles heel in the development of next-generation HEAs. Here, we demonstrate a pathway to homogenize the microstructure of a biocompatible dual-phase HEA, comprising refractory elements, namely, MoNbTaTiZr, through severe surface deformation using stationary friction processing (SFP). The strain and temperature field during processing homogenized the elemental distribution, which was otherwise unresponsive to conventional annealing treatments. Nearly 15 min of the SFP treatment resulted in a significant elemental homogenization across dendritic and interdendritic regions, similar to a week-long annealing treatment at 1275 K. The SFP processed alloy showed a nearly six times higher biocorrosion resistance compared to its as-cast counterpart. X-ray photoelectron spectroscopy was used to investigate the nature of the oxide layer formed on the specimens. Superior corrosion behavior of the processed alloy was attributed to the formation of a stable passive layer with zirconium oxide as the primary constituent and higher hydrophobicity. Biocompatibility studies performed using the human mesenchymal stem cell line, showed higher viability for the processed HEA compared to its as-cast counterpart as well as conventional metallic biomaterials including stainless steel (SS316L) and titanium alloy (Ti6Al4V).

A novel NDE approach towards evaluating adhesive bonded interfaces

Aerospace structural components are made by adhesively bonded layers of different materials for achieving specific properties for industrial applications. One such advanced structural material is made of glass fibre reinforced plastic (GFRP) composite. This is a layered engineered material with composite adhesively bonded to rubber to one of the surfaces. Such engineered materials can withstand structural, thermal and corrosive environments. GFRP composite have to be bonded with rubber using rubber solution or other adhesive to keep them structurally bonded. Any separation of these two layers will make the engineered structure redundant. In this paper, we report application of various NDE methods for evaluating bonded interfaces of engineered structural composite materials. Conventional methods such as X-ray radiography and ultrasonic (acousto-ultrasonic) methods were experimentally verified for identifying defects at the adhesively bonded interfaces. Disadvantages of these conventional methods were overcome by using advanced single sided nuclear magnetic resonance (NMR) technique. The use of low frequency single sided portable NMR for characterising defects at the adhesively bonded interfaces is discussed. In addition to the defect detection, application of NMR for measuring thickness of adhesive layers coated over rubber is also presented. Advantages of using NMR technique over other conventional methods is discussed.

Titanium in Shipbuilding and Other Technical Applications

Aerospace industry is currently the major consumer of titanium in Russia. Shipbuilding is its second largest consumer. Oil and gas, chemical, pulp-and-paper and other industries use less titanium. In the Russian industrial sector titanium is geting more applicable. Since the 13th World Ti-2015 Conference the titanium application trends have persisted [1]. Among the major development trends of titanium alloys one should note the development of titanium alloys for deep-water marine facilities, case designs of small-size nuclear power plants, the development of additive technologies, the technologies of isostatic pressing, the development of titanium products by new production facilities, etc. Titanium is still considered an advanced structural material used for scientific and technical progress in different industrial sectors.

A Method to Determine Material Length Scale Parameters in Elastic Strain Gradient Theory

Abstract With specimen size decrease for advanced structural materials, the measured mechanics behaviors display the strong size effects. In order to characterize the size effects, several higher-order theories have been presented in the past several decades, such as the strain gradient theories and the micro-polar theories, etc. However, in each higher-order theory, there are several length scale parameters included, which are usually taken as the material parameters and are determined by using the corresponding theoretical predictions to fit experimental results. Since such kind of experimental approaches needs high techniques, it is very difficult to be performed; therefore, the obtained experimental results are very few until now; in addition, the physical meanings of the parameters still need to be investigated. In the present research, an equivalent linkage method is used to simply determine the elastic length parameters appeared in the elastic strain gradient theory for a series of typical metal materials. We use both the elastic strain gradient theory and the higher-order Cauchy-Born rule to model the materials mechanics behaviors by means of a spherical expanding model and then make a linkage for both kinds of results according to the equivalence of strain energy densities. The values of the materials length parameters are obtained for a series of typical metal systems, such as the face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) metals.

Dispersing of functionalized CNTs in Si–O–C ceramics and electromagnetic wave absorbing and mechanical properties of CNTs/Si–O–C nanocomposites

Advanced structural materials with excellent electromagnetic wave (EMW)-absorbing properties and outstanding mechanical properties have stimulated attention in recent years. The application of CNTs as excellent EMW absorbers in ceramic matrix composites has been limited due to the difficulty of homogeneously dispersing these CNTs. Herein, CNTs/Si–O–C nanocomposites were synthesized by a polymer-derived ceramics method using polysiloxane (PSO) as a precursor and functionalized CNTs as fillers, and the CNTs/PSO precursors were pyrolyzed at 800 °C under Ar atmosphere. The carboxyl CNTs (CNTs-COOH) could be steadily suspended in PSO/ethanol solution for a longer time compared with pristine CNTs and hydroxylated CNTs (CNTs-OH); these results revealed that CNTs-COOH can disperse homogeneously in PSO/ethanol solution due to stronger electrostatic repulsions with each other and strong binding forces with PSO and ethanol. The effects of the loading ratio of CNTs-COOH on the EMW-absorbing properties at the X band (8.2–12.4 GHz) and the mechanical properties of CNTs/Si–O–C nanocomposites were investigated. When the filler loading ratio was 7.5 wt %, CNTs/Si–O–C nanocomposites had a minimum reflection loss of -60.40 dB at 10.15 GHz with a thickness of 2.5 mm, and the effective wave absorbing band covered 3.11 GHz (8.78 GHz–11.89 GHz). The flexural strength was significantly enhanced from 5.70 MPa of Si–O–C ceramic to 12.50 MPa with 7.5 wt % CNTs and 23.74 MPa with 10.0 wt % CNTs.

Evaluating and modeling rate sensitivity in advanced reactor structural materials: 316H, Gr. 91, and A617

Advanced reactor systems operate at high temperatures to achieve better thermal efficiency. During transients from lower temperatures to high operating temperatures structural metals transition from rate insensitive behavior to rate dependent behavior. In the rate dependent regime creep and plastic deformation are not separable hence requiring a unified treatment with a viscoplastic model. Several bounding design methods in the ASME Boiler and Pressure Vessel Code, Section III, Division 5, Subsection HB, Subpart B assume a decoupled treatment of creep and plasticity so establishing the boundary of the rate insensitive regimes for advanced reactor structural materials is necessary to set limits for the use of these bounding design methods. In the rate sensitive regime new bounding methods or fully inelastic analysis are required for the design of Division 5 Class A components. During temperature transients these components may operate in both the rate insensitive and rate sensitive regions, requiring computational models that can represent both types of behavior. This work establishes criteria for material rate sensitivity and develops a new composite method for modeling constitutive response in both the rate sensitive and rate insensitive regimes for three Division 5, Class A materials: 316H austenitic stainless steel, Grade 91 ferritic-martensitic steel, and Alloy 617, a nickel-based alloy. Both the criteria and new modeling strategy apply the concept of a normalized activation energy for thermally activated mechanisms developed by Kocks, Mecking, and co-workers. This work quantifies the average rate sensitivity of the three materials from an experimental database collected from the literature. Additionally, this work develops rate sensitivity criteria and a complete model for each material that can transition between both deformation regimes and provides several example simulations demonstrating the accuracy of the models and the numerical performance of the composite modeling method.

Advanced Structural Fibre Material for Single Link Robotic Manipulator Simulation Analysis with Flexibility

Advanced Structural Fibre Material for Single Link Robotic Manipulator Simulation Analysis with Flexibility

A carbon fiber thermoelectric generator integrated as a lamina within an 8-ply laminate epoxy composite: Efficient thermal energy harvesting by advanced structural materials

For the first time, the fabrication of a thermoelectric generator (TEG) consisting of carbon fiber (CF) tows and its integration as a lamina within an 8-ply laminate epoxy composite is reported. Commercially available M40B and A-38 CF tows exhibited a Seebeck coefficient (S) of +33.85 μV/K (p-type) and −11.83 µV/K (n-type), respectively. Scanning electron microscopy highlighted the CF morphological characteristics and the fiber mean diameters. Electrical conductivity measurements revealed the extremely high values of 1.63 ± 0.04 × 105 S/m for the CF-M40B and 1.14 ± 0.03 × 105 S/m for the CF-A38. CF-M40B of 33.4 mm length were employed to fabricate a TEG consisting of ten serially interconnected thermocouples. The TEG-enabled CF reinforced polymer (CFRP) composite consisted of unidirectional fabrics at an alternating [0/90]2s symmetric configuration, with the CF TEG module comprising the bottom lamina. The CFRP TEG laminate exhibited a voltage output of 19.56 ± 1.31 mV at a temperature difference (ΔT) of 75 °C. A reference CFRP was tested in terms of mechanical performance via three point bending and compared to the TEG-enabled one. Finite Elements modeling validated the CFRP thermoelectric performance corroborating the experimental findings. Structural TEG-enabled CFRPs demonstrated for the first time in this work are envisaged to harvest thermal energy losses on a large scale during the operational lifetime of advanced composites.