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Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on the microstructural evolution, mechanical properties, and corrosion resistance of SLM samples was investigated. Microstructural investigation showed a considerable grain refinement in the friction stirred area, which is due to the severe plastic deformation and dynamic recrystallization of the material in the stir zone. Micro-hardness measurements revealed that the micro-hardness values of samples treated using FSP are much lower compared to SLM components in the as-built condition. This reduction of hardness values in samples treated with FSP can be explained by the dissolution of the very fine Si-phase network, being characteristic for SLM samples, during FSP. Surface topography also demonstrated that the FSP results in the reduction of surface roughness and increases the homogeneity of the SLM microstructure. Decreased surface roughness and grain size refinement in combination with the dissolved Si-phase network of the FSP treated material result in considerable changes in corrosion behavior. This work addresses the corrosion properties of surface treated additive manufactured Al-Si12 by establishing adequate microstructure-property relationships. The corrosion behavior of SLM-manufactured Al-Si12 alloys is shown to be improved by FSP-modification of the surfaces.

The conditions for increasing the hot workability and extending the temperature range for the safe hot working of M2 high-speed steel (HSS) were studied and revealed. This was enabled by combination of two approaches, i.e. results obtained by an analysis of so individual as well as spatial influences of chemical elements on the hot workability using a conditional average estimator neural networks in combination with the results obtained from hot-compression tests that revealed the appropriate soaking conditions. The Latin Hypercube Sampling technique was used to model the uncertainty of the collected data used in the analysis. The obtained results reveal new, surprisingly complex, typically spatial and (highly) non-linear relationships between the chemical elements and the hot workability of M2 HSS, i.e. common mutual influence of carbon, carbide-forming elements as well as elements, i.e. Si, Mn and Co, which indirectly influence the formation of carbides. Further also new allowed upper limits for contents of some harmful elements like S, P, Al, Sb, Cu, Sn, As, Ni, etc. at which transition from higher to lower workability takes place were revealed. Finally, by applying a specially developed procedure for hot-compression tests the appropriate soaking time and temperature were assessed. New findings explain and considerably improve the intrinsic hot workability and extend the temperature range for safe hot working at its upper and lower limits.

In recent years, numerous scientific and technological innovations have been introduced in the fields of medicine and dentistry. The application of computer-based engineering techniques has enabled significant improvement in the design and performance of biomedical components, including implants and prostheses. Innovative and flexible manufacturing methods, such as single point incremental forming (SPIF), allow the cost-effective production of these “custom-made” components. The SPIF technology has been employed to manufacture a metal denture base plate (framework) of a complete maxillary (upper) denture to replace a traditional prosthodontic procedure based on a lost-wax technique, which is time-consuming and requires much manual work. Stainless steel sheet of quality X6Cr17 and thickness of 0.5 mm was adopted due to its biocompatibility, good mechanical properties, and reasonable price. The SPIF process was completely designed in a digital environment with a focus on achieving high quality and accuracy of the part followed by experimental verification. For validation, the formed part was compared in terms of the geometry and mechanical strength with the reference one fabricated using the lost-wax technique. The results obtained confirmed the high dimensional accuracy and good strength of the SPIF-made part. The experimental investigations also included analysis of sheet thinning, surface roughness, and microstructure.

In this study, the development of surface features of Inconel 718 samples fabricated by selective laser melting under different laser powers and scanning speeds has been studied and correlated with the powder melting behaviors through both experimental and modeling approaches. The interaction between laser beam and powder particles was studied by a three-dimensional model using the height function-lattice Boltzmann method. Different process parameters were introduced to perform the simulations, revealing the underlying physics of the surface morphology. Through the calculation of the surface forces, some new insights were given about the powder melting behaviors and the resultant surface features. It was found that the surface tension rather than recoil pressure pulled the melted powder into the molten pool during the SLM process. As for low energy input, the powder tended to fuse together with the neighboring particles before entering the molten pool, which was found to be the main cause of the formation of surface fluctuations and the subsequent surface pores. To some extent, the existence of recoil pressure was favorable for a relatively stable flow and a flat surface morphology. The simulation results of the top surface morphology were compared with experimental results, and they were in good agreement.

A multi-functional composite coating was fabricated on magnesium (Mg) AZ31 alloy through micro-arc oxidation (MAO) combined with self-assembly technology. Polyethyleneimine (PEI) as a medium was assembled on MAO coating based on the chemical bonding and electrostatic interactions. Adhered PEI successfully mediates the self-assembly of functional silver nanoparticles (Ag NPs) with a formation of Ag NPs/PEI/MAO (APM) composite coating. The morphology and microstructure of as-prepared APM coating were characterized by using of different technologies (e.g. scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy). Its corrosion behavior in simulated body fluid and the corresponding antibacterial performance against Staphylococcus aureus (S. aureus) were also investigated. The potentiodynamic polarization results showed that the corrosion current density of APM coated AZ31 decreased more than three orders of magnitude in comparison with that of uncoated AZ31, indicating an enhanced anticorrosive ability. Electrochemical impedance spectroscopy results further revealed that the improvement of corrosion resistance was attributed to a synergistic effect of Ag NPs/PEI and MAO. The hydrogen evolution tests confirmed that APM coating provided AZ31 an excellent corrosion protection during a relatively long term. And the antibacterial research showed that APM coated AZ31 had a great antibacterial activity. This study presents a promising approach to fabricate a multi-functional composite coating on Mg alloy, which improves the anticorrosive performance of the substrate and endows it an antibacterial activity to meet a better demand in the applications.

The target of this research study was to evaluate the shear-tensile and fatigue behavior of aluminum 6061 alloy welds, in two different heat treatment conditions, joined by the recently developed intermediate layer friction stir spot welding (FSSW) technique. The keyhole, which is the disadvantage of the conventional FSSW process, was avoided using an additional intermediate layer (IL) accompanied by a simple tooling. Shear-tensile experiments demonstrated acceptable mechanical performance of IL-FSSW joints in comparison with that obtained using alternative methods. Fatigue behavior of the joints revealed a dependency to pre-processing temper especially at high cyclic load levels with improved life for the aged condition. Observations on the failure regions under shear-tensile experiments exhibited plug type and shear-plug type fracture modes for the aged and annealed conditions, respectively. In contrast, the fracture mode showed variation with respect to the load level but not to the type of temper during cyclic loading.

In order to study the factors of columnar to equiaxed transition (CET) of high-Nb TiAl alloys, Ti46Al7Nb0.4W0.6Cr0.1B alloy has been fabricated by cold crucible directional solidification (CCDS) technique under different pulling rate from 3.3 μm/s to 16.7 μm/s. The marco/micro-structure and phase composition near solid–liquid interface have been characterized. Results show that the CET of the high-Nb TiAl alloy occurs with the increase of the pulling rate at the constant temperature gradient. The microstructure of the columnar grain is composed of α2/γ lamellar matrix and a coupling structure of striped-like B2+γ phases. The lamellar colonies in a columnar grain possess the same orientation, while the arrangement direction between the striped-like B2 phase and growth direction is 0° or 45°. A solidification map for CCDS is established which predicts columnar or equiaxed morphology according to the growth rate (R) and temperature gradient (G). The dendrite morphology at the solid–liquid interface after quenching and the CET is controlled by the actual temperature gradient at the tip of the dendrite. Meanwhile, the increase of growth rate and the satisfaction of heterogeneous nucleation conditions are the main factors for CET. The decrease of actual temperature gradient caused by quenching or the increase of liquidus gradient caused by increasing growth rate can increase the maximum supercooling degree ΔTC. When it reached the supercooling degree ΔTN required to form a new nucleus, equiaxed grains will be produced. In addition, the boride in this alloy can act as a heterogeneous nucleation core to promote CET.

The films of alizarin yellow GG (AYGG)–CuCl2 blended with polyvinyl alcohol (PVA) have been successfully synthesized by casting method. The results show that the dielectric properties of AYGG–Cu(II) blended with PVA are enhanced by lowering selected frequency while σac(ω) increases monotonically with frequency, acting in accordance with the correlated barrier hopping model. At low temperature, the DC electrical resistivity of AYGG–Cu(II) blended with PVA film is temperature independent, while it is decreasing with high temperature. Al/(AYGG – Cu(II) blended with PVA)/ITO is fabricated as organic photovoltaic cell, concluding that there are many mechanisms can control the current flow. Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell under illumination of green light be most effective compared to illuminations of others. It is concluded that Al/(AYGG – Cu(II) blended with PVA)/ITO solar cell is very important, with potential advantages such as low cost and low-temperature fabrication processes. It is recommended that this material can be used in different applications such as temperature sensors, inrush current limiters, thermistors, and NO2 sensor.

This paper presents a novel approach to investigate the relations between drilling signals and bit wear condition in real world full-scale mining operations. This research addresses the increasing demand for automation in mining to increase the efficiency, safety, and ability to work in harsh environments. A crucial issue in fully autonomous unmanned drilling is to have a system to detect the bit wear condition through the drilling signals analysis in real time. In this work, based on extensive field studies, a novel qualitative method for tricone bit wear state classification is developed and introduced. The relations between drilling vibration as well as electric motor current signals and bit wear are investigated and bit failure vibration frequencies, regardless of the geological conditions, are introduced. Bit failure frequencies are experimentally investigated and analytically calculated. Finally, the effect of bit design parameters on the failure frequencies is presented for the application of bit wear condition monitoring and bit failure prediction.

Soft zone formation in dissimilar Cr–Mo welding occurs during post weld heat treatment that could compromise the integrity of the weldment. The decomposition of martensite could cause this formation at the weld heat affected zone adjacent to the fusion boundary. There could not yet determine the actual width of this zone. The extent of martensite decomposition in soft zone Cr–Mo steel dissimilar weld was observed in semi in-situ stages using the x-ray absorption spectroscopy (XAS) at Synchrotron facility. 2.25Cr–1Mo was welded using ER90S–B9 using GTAW process. PWHT was performed at 730 °C for 0.5 h and 2.0 h in a chamber with opening for Synchrotron light analysis at various locations away from the fusion boundary. This was complemented by microstructure and grain size analysis. The results showed the decomposition of martensite started at the fusion boundary and could extend beyond 1000 microns covering both CGHAZ and FGHAZ. Since the experiment was performed in normal atmosphere, the oxide film could form during PWHT on the surface of the specimen. More oxide formed was observed more in the location with high carbide contents. There was more oxide formation at the locations further distance from fusion boundary due to less martensite decomposition. Therefore, the extent of the phenomena could be stated by using information from oxide formation and martensite decomposition which could help to determine the risk on both creep life and oxidation.

High-speed impact tests were conducted in transverse direction with strain rates (SRs) ranging from 1000 s−1–6000 s−1 to investigate the deformation mechanism and adiabatic shearing behavior of extruded Mg-8.0Al-0.1Mn alloy in as-extruded (AE), low temperature solution-treated (ST1) and high temperature solution-treated (ST2) states. At SR of 6000 s−1, the flow stress exhibits a slight drop after reaching its peak, except that of the ST2 sample. The highest strain rate hardening results in the highest peak stress of the ST1 sample. Deformation is first dominated by basal slip, and then gradually converts to be dominated by a coordinated mechanism between basal slip and twinning. In late stage, it shifts to be dominated by non-basal slip supplemented with twinning and basal slip, and then by a coordinated mechanism between non-basal slip and dynamic recrystallization (DRX). Heat treatment only affects the scope of the dominated mechanism. The adiabatic shear band occurs only at SR of 6000 s−1 with strain of 0.30, which strongly affects the crack propagation and DRX. Interestingly, the DRX only occurs in the AE sample due to the combined effect of adiabatic temperature rise and pre-existing twins.

Magneto-optical Kerr effect (MOKE) microscopy is a versatile technique to image magnetic domains and evaluate the behavior of magnetic materials. However, MOKE has been rarely applied to the research of low magnetic steels with complex microstructure including micron-sized features. This study reveals the potential of implementing MOKE microscopy for analyzing the microstructure and stress state of martensitic steels with high carbide density (example conducted on AISI M2 steel grade). For the first time, the resulting MOKE domain images are used to analyze the size and morphology of martensite lath structures without chemical etching of the material's surface. Furthermore, MOKE microscopy allowed the confirmation and volumetric fraction estimation of retained austenite, despite the small size and volumetric fraction of under 1%. The validity of the MOKE microscopy analysis is cross-checked with scanning electron microscopy of etched samples and X-ray diffraction. Finally, MOKE microscopy in combination with Vickers indentation is applied to determine the residual stress state of the selected steel, which was varied by processing the steel material with conventional heat treatment scheme and heat treatment including deep cryogenic treatment (DCT). The method is proven effective in indicating the residual stress qualitatively. The measurements proved, that the residual stresses are significantly reduced in DCT steel samples, as theoretically anticipated. The conducted pioneering work provides important research towards the application of MOKE microscopy for the research of steel microstructure, properties and residual stresses as well as delivers a new perspective for determining the effectiveness of DCT on the steel properties.

With increasing depth of exploration and process boreholes (at small drilling diameters), the probability of deviation of the borehole path from design trajectory increases many times; i. e. zenith curvature and azimuth deviation of the borehole path occur. Therefore, developing methods for keeping vertical path of the borehole when drilling deeper horizons of ore bodies is a very topical issue. The paper presents the results of developing a new bottom-hole assembly for drilling boreholes in soft rocks using screw casing centralizers, which provide good stabilizing and centering effects to mitigate horizontal departure of the hole axis from the design direction and minimize vertical curvature of the hole path (zenith angle) while maintaining sufficient drill string flexibility. The developed technical solutions provide simplicity of design and ability to adapt to wide range of mining, geological and technological drilling conditions. The feasibility of manufacturing the centralizers by own efforts and the technological feasibility of quick and easy connecting the centralizer with other elements of the bottom-hole assembly have been substantiated. The manufacture efficiency is proved by the use of inexpensive and wear-resistant materials in the centralizer armouring, for which tungsten-cobalt or titanium-cobalt hard-alloy inserts were used. In addition, prevailing volume of borehole drilling in soft rocks allowed using replaceable centering elements, as well as their repair and restoration to increase their service life. The manufactured centralizer has a low production cost due to the design simplicity and the use of inexpensive wearresistant material and will compete in the market of drilling tools and technical devices for drill string stabilization. The economic effect from the introduction of the self-produced centralizers amounted to more than 170,000 tenge per a borehole.

The microstructural evolution and mechanism of grain refinement during rapid solidification of Ni–Cu alloys were studied by molten glass purification and cyclic superheating. The maximum undercooling has achieved 320 K for Ni65Cu35, 295 K for Ni55Cu45 and 280 K for Ni50Cu50 alloys. Two mechanisms were found to be responsible for the grain refinements under small undercooling and large undercooling, respectively. The grain refinement at small undercooling is mainly caused by dendrite superheating and remelting, whereas that for large undercooling is mainly due to recrystallization occurred at high angle grain boundary and high proportion of twin boundaries. Meanwhile, almost no dislocations and other defects were observed in the substructure of the alloy with large undercooling.The average microhardness was found a sharp decrease in the alloy with large undercooling, which indicates that the plastic strain accumulated in the microstructure formed under large undercooling is completely dissipated in post-recalescence, and the deformation energy can offer the driving force for recrystallization in the microstructure.

Quenching and partitioning (Q&P) treated steels are traditionally alloyed with silicon (Si), but its precise role on microstructural mechanisms occurring during partitioning is not thoroughly understood. In this study, dilatometric analysis has been combined with detailed microstructural characterization to unravel the competing mechanisms occurring during partitioning either in parallel or in succession. Three 0.4 wt.% carbon steels with varying Si contents were quenched to 150 °C for ~20% untransformed austenite, and partitioned for 10–1000 s in the temperature range 200–300 °C. The steel with low Si content (0.25 wt.%) exhibited substantial bainitic transformation during partitioning at 300 °C and only 4% retained austenite (RA) at room temperature (RT) even after 1000 s hold. In contrast, a high Si fraction (1.5 wt.%) enabled retention of ~18% austenite under similar conditions. While η-carbides precipitated within the martensite laths in the high-Si steel, cementite precipitated in the low-Si variant. Furthermore, carbide precipitation and growth were strongly suppressed by high Si content. Secondary martensite formation occurred from carbon-enriched austenite during final cooling, irrespective of Si-content. Results illustrate that Si retards austenite decomposition at higher partitioning temperatures but does not improve carbon partitioning at lower temperatures.

The oxidation kinetics, oxide layers composition and thicknesses of X70 steel, Y55 steel and 304 stainless steel are investigated. The results show that the oxidation rate of X70 steel increases rapidly at 1000 °C, while that of Y55 steel and 304 stainless steel increases rapidly at 1100 °C. The oxidation kinetic coefficients of X70 steel, Y55 steel and 304 stainless steel are exp (10.7), exp (11.58) and exp (30.15), respectively, and the apparent activation energy of oxide layer are 196879.7 J/mol, 207608.1 J/mol and 469284.3 J/mol, respectively. The cross-sectional morphology and element distribution of oxide layer are obtained. With the oxidation time increases from 30min to 80 min at 1100 °C, the oxide layer thickness of X70 steel and Y55 steel increases by 1242.33 μm and 965.59 μm respectively when the weight of steels increases by 1 mg/mm2, and the oxide layer of Y55 steel is denser than that of X70 steel. A variable temperature oxidation mathematical model of the slab surface is established to predict the oxide layer thickness of slab surface.

The potentiality on alkali activation of volcanic tuff with calcium-based materials, fly ash, and their mixtures as additives were comprehensively investigated in this study. Several characterization strategies have been employed for mechanism exploration. CaO and fly ash (FA) brought about more dramatic responses than CaSO4 and alkaline activator on activating the volcanic tuff-based geopolymer, which was relatively stable under the wet-dry alternated conditions. The symmetrical stretching vibration of Si–O–T (T = Al or Si) was right-shifted to the band at approximately 1036 cm−1, implying the incorporation of Ca into Si–O–T. FA accompanying with CaO enhanced the polycondensation, gelation, and hardening of geopolymer. However, too many quartz balls brought into geopolymer paste by an excessive amount of fly ash deteriorated the cementing quality and reduced the mechanical strengths. This work contributes to the module usage of volcanic tuff in the construction industries and supplies an innovative method in activating geopolymerization.

Aluminium alloys are one of the choice materials with ever-increasing demands in manufacturing industries. The aluminium alloy 6 xx series such as AA6061-T6, has emerged as one of the promising materials utilized owing to its combination of favourable properties which include high strength to weight ratio, good ductility, excellent corrosion resistance and relatively low cost. These superior properties are responsible for its emergence and usage in the fabrication of aircraft wings and fuselages, yacht/ship construction, automotive rims and wheel spacers. However, joining of AA6061-T6 including the use of friction stir welding (FSW) has serious concerns because the mechanical and tribological properties of the AA6061-T6 welded joints deteriorate significantly compared with the base metal. This phenomenon has been attributed to the severe softening encountered at the stir zone (SZ) of the aluminium matrix during FSW. Other inherent challenges of FSW such as weld thinning, kissing bond and keyhole formation also contribute to the reduction in the weld joint quality. The softening phenomenon has been linked to the dissolution of the strengthening precipitates (B″-Mg5Si6) as a result of high heat input during the welding process. Hence, this paper attempts to review the various improvement strategies adopted in the existing studies to improve the quality of AA 6061-T6 welded joint. These include parametric optimization, selection of appropriate tool design, pre and post heat treatments, adoption of different groove/hole designs for particle addition as well as the addition of reinforcement particles to the weld joint. The variants of FSW recently developed will also be considered. The findings from the review will generally be useful for future work on FSW of heat treated aluminium alloys. The evolution of FSW and its associated challenges are briefly discussed while the research areas yet to be harnessed are suggested for future works.

The disintegration of Cu metal in 1 mol/L HCl and the mitigating effect of the expired Ceftazidime antibiotic were studied. The inhibition efficacy of Ceftazidime depends on its concentration in the medium. The mitigation efficacy increases from 77.7 to 94.2%, as the Ceftazidime concentration increases from 50 to 300 ppm in the corrosive medium. The polarization results confirmed that the antibiotic acts as a mixed-type inhibitor. The adsorption of the antibiotic on the Cu surface belongs to Timken's model. The adsorption constant, Kads, and the standard free energy change ΔGo were estimated. The adsorption of Ceftazidime drug follows a physical-type. Scanning microscopy (SEM) and energy dispersing X-ray (EDX) techniques demonstrated that the expired antibiotic molecules are firmly adsorbed at the copper surface. Electrochemical modulation (EFM), and polarization tests are in good agreement with the weight lack method.

The influence of size effect on deformation behaviors at quasi-static strain rate has been widely studied in recent years. However, there is little research about size effect on deformation behaviors of metal foils at high strain rate. To clarify how the size effect influences the deformation behavior of metal foils over a wide range of strain rate, the tensile tests at different strain rates of pure titanium foil with various grain sizes were originally conducted using material testing system (MTS) and a specially designed Split Hopkinson Tension Bar. It is found that microstructure evolution and fracture mechanism show great differences between quasi-static and dynamic tensile tests. Moreover, size effect on flow stress of pure titanium foil also shows obvious distinctions between quasi-static and dynamic tensile tests and this phenomenon was well explained by the proposed twinning refinement physics model. Furthermore, the uniform strain for pure titanium foil is larger at high strain rate than that at quasi-static strain rate, and a larger uniform strain for pure titanium foil with larger grains was observed at high strain rate. A modified Johnson-Cook model coupling effects of grain size and strain rate was proposed to predict the flow stress of pure titanium foil, and the prediction matched well with the experimental results.

In this study, a simplified approach to correlate the experimental tensile strength values of the randomly oriented short fiber (SF) reinforced polymer-based composites is presented. For this purpose, a constitutive model to correlate the experimental tensile strength values of SF reinforced composites is derived. The constitutive model was derived based on a rule of mixtures. The experimental results on the Short Carbon Fiber (SCF) reinforced composites reported in our earlier works show a non-linear increase in its tensile strength as the fiber volume fraction is increased. The experimental strength of the composite was found to be significantly dependent on the interfacial stress at the fiber–matrix interface and the percentage of fibers oriented in the loading (tensile) direction. Thus, the orientation dependence of the fibers was incorporated by assuming that the percentage of aligned fibers follow the Weibull Probability Distribution Function (PDF). Additionally, the derived constitutive model was verified against the reported tensile strength data of SCF composites. The correlations of the experimental results from our earlier published work and from other available data in the literature, with the proposed model, were found to be in good agreement. The analytical model was compared to other analytical models and found that the current model showed better agreement with the reported experimental results.

The hard roof difficult to collapse easily causes gas accumulation, which threatens the production safety of coal mine. Therefore, roof pre-cracking is required. Although blasting and hydraulic fracturing can also crack the roof, blasting can easily induce rock bursts, whereas hydraulic fracturing needs complex equipment. In contrast, soundless cracking demolition agents (SCDAs) with noise-free, dust-free, and safe characteristics have obvious advantages. The main component of SCDA is calcium oxide, which reacts with water to produce higher expansion pressure. In this paper, focused on the angles of the borehole, the effect of SCDA is analyzed by numerical simulation based on Pingdingshan coal mine. The research results showed that the azimuthal angle α (between borehole projection and the roadway direction) does not significantly affect the efficacy of SCDAs, whereas the influence of borehole elevation angle β is far more significant than that of the azimuthal angle. Therefore, the angle β is a dominant factor influencing the effect of SCDAs. Based on different effects of SCDAs at different angle of boreholes, the weakening unit was established, so the SCDAs could give full play to roof fracturing. Moreover, field tests validated the importance of borehole angle on weakening the hard roofs.

To explore the failure mechanism of roadway in layered soft rocks, a physical model with the physically finite elemental slab assemblage (PFESA) method was established. Infrared thermography and a video camera were employed to capture thermal responses and deformation. The model results showed that layered soft roadway suffered from large deformation. A three-dimensional distinct element code (3DEC) model with tetrahedral blocks was built to capture the characteristics of roadway deformation, stress, and cracks. The results showed two failure patterns, layer bending fracture and layer slipping after excavation. The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs. Six schemes were proposed to investigate the effects of layered soft rocks. The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata. When the roadway was completely in a coal seam, the change of deformation in ribs was not obvious, while the deformation in the roof and floor increased obviously. These results can provide guidance for excavation and support design of roadways in layered soft rocks.

Composite materials for vehicle parts require lightweight, high strength and good impact properties. In this study, the optimized manufacturing conditions of epoxy foam (EF) were investigated to improving mechanical performance of carbon fiber reinforced plastic (CFRP)/EF/CFRP sandwich composites for vehicle parts such as impact, flexural property. The optimal curing temperature was found to be 60 °C, by measuring the reaction rate, volume increase rate, density, cell size, glass transition temperature, and specific compressive strength of the EF. In addition, foams after 180 °C thermal aging were observed, and the properties of the EF cured at 60 °C were the most stable under the thermal aging. The performance of the sandwich EF composites was investigated using compressive, flexural strength, lap shear strength, and impact tests. The optimized cell condition of the EF was correlated to improving interfacial adhesion of sandwich composite.

In structural applications, catastrophic failure caused by fatigue occurs with more frequency because usually polymers are chosen when reduction in weight is necessary and overload is applied on it. In this study fatigue, crack growth at a humid, and very low temperature in a transparent unsaturated polyester resin has been investigated. The tests were conducted at a constant applied load ratio R = 0.1 using two different crack to width ratios (a/W) of 0.2 and 0.35 at room temperature and −60 °C. Polyester resin specimens are fabricated. The test used for the experiments is ASTM Standard D647 under tension–tension loading. The experimental results have been expressed in terms of Paris Law parameters. The fatigue crack results show that the fatigue resistance increases with decreasing a/w. It also shows that it increases with decreasing temperature up to −60 °C as the material becomes stiffer at the extremely low temperature and the polymer matric particles were much less mobile and ductile and discovered that low temperature has a positive influence on the strength of composites. The dominant failure mode was a polymer matrix -tear failure that was driven by a crack in the x-direction starts with the pre-crack in the case of a/w = 0.35 and it was slow enough in a/w = 0.2 because of the high energy of bonding and networking through the polymer matrix. The results proved that there is no through-the-thickness crack propagation due to fatigue in the polyester matrix.

A nanobainitic matrix composing of nanoscale α phase and carbon-riched γ phase was obtained for the ductile iron by austempering treatment. The microstructure and properties of ductile iron were compared with GCr15. The microstructural characteristic gave rise to a good strength with an ultimate tensile strength higher than 1200 MPa, which was comparable and even superior to conventionally forged steels. The friction coefficient of the ductile iron was approximate 1/3 compared with that of commercial GCr15 under dry sliding wear condition, which was related to the existence of homogeneously distributed spheroidal graphite in ductile iron. The low friction coefficient and moderate strength resulted in a superior wear resistance of ductile iron with nanobainitic matrix by contrast to GCr15.

The ultrasonic shot peening (USP) treatment was adopted to improve the compressive residual stress, microhardness and corrosion resistance of Ti–6Al–4V (TC4) titanium alloy fabricated by selective laser melting (SLM). The optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and hardness test were used to investigate the microstructure evolution. The effect of the USP on electrochemical behaviour of the SLM TC4 alloy in a 3.5 wt. % NaCl solution was studied using potentiodynamic polarization. After USP treatment, compressive residual stress was induced and microhardness significantly increased. Proper USP treatment can effectively improve corrosion resistance of the SLM TC4 alloy, which is manifested by the increase in corrosion potential and decrease in corrosion current density.

The increasing environmental problems as well as demand of energy encourage the research for safe as well as efficient energy sources. As most of the energy sources are not consistent; thus, there is a requirement for highly efficient energy storing systems. Supercapacitors emerge with great researcher interest because of their very high capacity of storing energy. The performance and efficiency of supercapacitor depends directly on the electrode materials. The oxides of transition metals are highly explored as pseudo capacitors material. Nickel based electrode materials, characterized by ultrahigh theoretical capacitance has gained significant attention. These days nickel oxide-based electrodes owing to their high chemical stability, good theoretical specific capacitance, less cost, easy availability as well as non-toxic nature makes it very popular. This review deals with the recent development in the field of nickel-based supercapacitor electrodes by grouping them on the basis different morphologies such as nanoparticles, nanowires, thin films, nanofibers, etc along with challenges as well as future research.

This study presents microstructural, electrochemical, and mechanical characterizations on pure copper fabricated using constrained groove pressing (CGP) in quiescent phosphate buffer solution (pH = 11.73). We tested the effect of surface modifications on electrochemical features using electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. A three-dimensional simulation via finite element modeling evaluates the CGP effects on the maximum principal stress and the plastic strain distribution. The transmission electron microscopy (TEM) micrographs confirm that the increasing CGP cycles result in a nano/ultrafine grain microstructure. Our electrochemical study showed that the CGP process can positively impact the passive behavior of pure copper. Mott–Schottky analyses illustrated that the point defect densities decline in the p-type semiconducting passive layer upon receiving CGP. Besides, increasing the CGP cycles lowers the corrosion current density and produces less defective passive films.

The present work, first detailed study in its nature, introduces wall curl as a source of geometric inaccuracy in the novel Incremental Sheet Forming (ISF) process, and aims at investigating role of the residual stresses, stretching force and process conditions on formation of the curl. A series of metal components are formed by varying the conditions. The curl height, residual stresses (surface, mean and equivalent) and stretching force are determined and their correlations are analyzed. The analysis reveals that curling is strongly influenced by the residual stresses in a way that the curl height increases linearly as their magnitude increases. Similarly, an increase in degree of non-uniformity in the through-thickness stress distribution promotes curling. The increase in stretching force, however, diminishes curling reasoning to reduction in the residual stresses. As regard the conditions, feed rate does not show any effect while mild annealing, greater tool diameter, smaller step size, and lower forming angle and rotation are found conducive to minimize curling. The geometric errors in wall and bottom of the produced parts (i.e., curling and pillowing) are found to show an interesting inverse relationship. The reported results are very useful to deepen the process mechanics and will also prove helpful in simultaneously controlling the two types of errors.

The tensile-shear strength of laser-welded lap joints developed in abrasion resistance ultra-high strength ARS-600 steel was optimized by evaluating the joints achieved with different welding parameters and various configurations of weld patterns, including multiple continuous longitudinal and transverse weldments. The microstructural evolution of the fusion zone was characterized by electron backscatter diffraction (EBSD) after welding with different values of energy input (60–320 J/mm). Furthermore, in order to better comprehend the shear response of different weld patterns, stress analysis of various longitudinal and transverse lap joints was conducted by the finite element method (FEM).

This article presents the results of an experimental investigation on the mechanical behavior of hybrid fiber reinforced Strain Hardening Cementitious Composites (SHCC) subjected to monotonic and cyclic loadings. For the study, PVA, ultra-high molecular weight polyethylene (UHMWPE) and steel fibers were used in a constant volume fraction of 2.0%. To study the synergetic effects between the fibers, hybrid compositions were also produced by replacing PVA and polyethylene by steel fibers in 0.5% and 1.0% volume fractions. The mechanical response was measured under direct tension tests, four-point bending tests on plates and three-point bending tests on notched specimens while the crack pattern was investigated using optical microscopy. To study the mechanical performance of the materials when subjected to loading/unloading cycles, cyclic three-point bending tests were also carried on. The partial replacement of PVA and polyethylene fibers by steel fibers increased the strength and post-cracking stiffness but reduced the ductility of the composites. The hybrid SHCCs presented a good mechanical performance when subjected to cyclic loadings, since the load bearing capacity and the multiple cracking behavior were maintained even for high crack opening values. The stiffness degradation and the dissipated energy over the loading/unloading cycles varied when different fibers combinations were used.

Fracture Forming Limit Diagram (FFLD) is gaining special attention for high strength materials like Inconel 718 alloy where the substantial necking tendency rarely seen. The present study mainly aims at accurate evolution of forming limits for Inconel 718 alloy with an improved Marciniak–Kuczynski (M–K) model coupled and various ductile fracture criteria. Firstly, uniaxial test has been performed for analyzing material properties and anisotropic parameters. The stretch forming tests have been conducted to evaluate the limiting forming limits of Inconel 718 alloy. Subsequently, an improved M–K model coupled with ductile fracture criteria has been developed for the theoretical prediction of the fracture strains. The different ductile fracture criteria, namely; Clift, Cockcroft and Latham, Oyane and Brozzo, have been implemented in the improved M–K model. A Newton–Raphson method has been used to solve improved M–K model. The improved M–K model coupled with Oyane's fracture criterion has shown good predictability of the fracture loci with the least average absolute errors and root-mean-square deviation ( Δ avg = 0.075 and RMSD = 0.105).

In this study, 6056 aluminum alloy produced through continuous casting direct rolling (CCDR) was investigated. This alloy is used in the automotive industry because of its high corrosion resistance and strength. However, the material may become embrittled as a result of excessive deformation during cold forging. Therefore, preheat treatment was employed to improve the formability of 6056 aluminum alloy. Five different preheating conditions were considered in this study: annealing (O), solution treatment (W), aging for 2 h at 195 °C after solution treatment (SPA195), aging for 2 h at 230 °C after solution treatment (SOA230), and aging for 2 h at 250 °C after solution treatment (SOA250). The results show that the over-aged specimen SOA250 exhibited the best formability and could compress 85% of the original diameter after cold rolling. However, the ductility decreased considerably after cold rolling. To increase ductility and strength, a T6 treatment was applied after cold rolling. The ductility and strength of the specimen were increased significantly, similar to the manner in which the ductility and strength of a raw material that has undergone T6 heat treatment. The CCDR 6056 aluminum alloys subjected to solution treatment and over-aging treatment exhibited good cold rolling formability, and with the subsequent T6 heat treatment, the alloys exhibited high strength and ductility. The materials can thus be used for the manufacture of automotive fasteners.

Post-weld slag and weld metal analyses were used to interpret the effects of different commercial flux compositions on element transfer between molten flux (slag) and weld metal in Submerged Arc Welding (SAW). Selected fluoride based flux compositions cover a wide range of basicity index (BI) values of 0.5–3.0. Thermochemical modelling in FactSage software is used to simulate the welding process in terms of gas-slag-metal equilibria. The importance of the gas phase in SAW element transfer is illustrated. The model provides improved accuracy in predicted weld metal oxygen values (ppm O) compared to the generally used empirical relationship of weld metal ppm O vs. flux BI. Model predicted oxygen values are within 150 ppm of the analysed values, compared to the empirical relationship values which are within 240 ppm from the analysed values. The model provides resolution in ppm O values at BI > 1.8. This information is lacking in the empirical relationship with constant ppm O of 250 ppm at BI > 1.8. The measured ppm O values follow the Fe–FeO equilibrium trend with a positive offset. The relative level of oxygen to deoxidation elements (Ti, Al, Mn, Si) in the weld metal is an important factor in oxide inclusion engineering. This model will aid in the specification of flux formulations to attain specific weld metal compositions for maximum acicular ferrite formation. In this way the weld metal mechanical properties can be improved. This model will reduce the number of welding tests required to develop new flux formulations.

Multiple seam interactions are a major source of ground instability in several U.S. coalfields. Empirical methods are well suited for this problem, because while the mechanics multiple seam interactions are very complex and poorly understood, many mining case histories are available for analysis. This study makes use of an updated database that includes 356 multiseam case histories, including 67 unsuccessful designs. The paper describes in detail the process used to design the study, collect the data, conduct the statistical analysis, and develop the quantitative model. The model can be used for mine planning in multiple seam situations, and has been made available as a module within the Analysis of Coal Pillar Stability (ACPS) computer program.

Glass-forming ability (GFA) of the Gd20Dy20Er20Co20Al20 high-entropy bulk metallic glass (HE-BMG) was improved through microalloying Si element. The critical diameter of this rare-earth-based HE-BMG increases from 1.5 to 8.5 mm with 0.5 at.% Si addition without any deterioration of magnetocaloric property. Compared with the Si-free sample, the BMG with 0.5 at.% Si addition exhibits low driving force for crystallization, strong supercooled liquid behavior and sluggish crystallization kinetics, whereas excessive Si addition leads to reverse variations. Furthermore, microalloying Si can enhance nanoscale heterogeneity of elemental distribution, and thus facilitates the formation of local crystal-like structures. The connectivity and competition between icosahedra-like clusters and crystal-like structures promote the formation of stable network structure which frustrates crystallization. As Si content is excessive, icosahedra-like cluster is consumed by the further grown crystal-like structure, leading to the destruction of network and decreasing GFA. This work not only elucidates the underlying mechanism of the GFA enhanced by microalloying, but also sheds light on improving the GFA of HE-BMGs through altering nanoscale elemental distribution and structural heterogeneity.

Grain boundary segregation engineering (GBSE) is a promising approach for accurately manipulating chemical composition, structure and properties of grain boundaries (GBs). With the aim of attenuating or even removing disadvantages of GBs in nickel-based superalloys, the GB segregation behaviors of 3d (Ti–Co), 4d (Zr–Rh) and 5d (Hf–Ir) transition-metal (TM) solutes X and their effects on the thermodynamic stability and fracture strength of Ni Σ3 [110](111) symmetrical tilt grain boundary were systematically investigated, using first-principles total-energy calculations based on density functional theory. We found that all TM solutes considered herein can segregate towards the Ni Σ3 [110](111) GB. For TM elements from same row of the periodic table, their segregation energies show a concave-up parabolic-like dependency on the atomic number of TM elements. The GB segregations of all considered solutes can lead to a reduction in GB energy and render the Ni GB more stable, and the GB energies of X-segregated GBs vary linearly with the GB segregation energies of solutes X. Except elements Zr, Hf and Rh, the GB segregations of the other 15 TM alloying elements increase the GB fracture strength. The Mn and Re segregations improve the GB fracture strength and thermodynamic stability to a maximum extent, respectively. The underlying mechanisms for segregation-induced GB stabilizing and strengthening effects were further revealed at the electronic level by analyzing the crystal orbital Hamiltonian populations and deformation charge densities. Our work could provide new insights into designing Ni-based superalloys with desired performances based on the concept of GBSE.

High niobium content TiAl alloys and Al2O3 ceramics were successfully joined using novel Nb particle-reinforced Ag–Cu composite filler. The changes in microstructure brazing at different temperatures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corresponding mechanical properties were studied by shear tests. The results showed that the brazed joints prepared at 900 °C can be divided into three zones. The typical microstructure of the brazed joints is high niobium content TiAl/AlCuTi + AlCu2Ti/Ag(s,s)+Cu(s,s)+Nb/Ti3(Cu,Al)3O/Al2O3. The brazing temperature was shown to have a significant influence on the microstructure and reaction layer thickness. After brazing at 810 °C, macrodefects could be observed in the brazing seam. At higher brazing temperatures, brazed joints without any defects were obtained. The addition of Nb particles and the suitable thickness of the Ti3(Cu,Al)3O reaction layer are the main reasons for the high shear strength. When brazing at temperatures higher than 900 °C, the volume fraction of the brittle AlCu(Ti, Nb) phase was increased and a thick Ti3(Cu,Al)3O reaction layer was formed, which deteriorated the shear strength of the joint. The maximal shear strength joint reached 228 MPa at 870 °C for 10 min, which is a substantial increase compared with conventional brazing processes.

The sulfuric acid industry produces large volumes of spent catalyst containing vanadium. To develop an efficient method for vanadium recovery, hydrogen peroxide was used to oxidize sulfur in the spent catalyst, forming sulfuric acid, which, in turn, leached the metals from the catalyst. Experimental results showed that the leaching efficiency of vanadium gradually increased with hydrogen peroxide concentration; other parameters had minor effects. The hydrogen peroxide concentration, stirring rate, and pH had negative effects on leaching percent of potassium. Leaching efficiency of iron decreased with an increase in leaching time, stirring rate, and pH; with the increase in hydrogen peroxide concentration and liquid:solid ratio, leaching efficiency of iron first increased and then decreased. The optimum leaching conditions for vanadium were hydrogen peroxide concentration of 148 g/L, leaching time of 5 min, leaching temperature of 25 °C, stirring rate of 300 r/m, and liquid:solid ratio of 3:1, and leaching efficiencies of vanadium, potassium, and iron were 92.2%, 48.2%, and 46.3%, respectively. For potassium and iron, the leaching efficiencies of 70.9% and 70.5% were achieved using pure water leaching under the conditions of leaching time of 30 min, liquid to solid ratio of 4:1, and the temperature of 25 °C.

The main purpose of this work was to synthesize ZnO nanoparticles (NPs) in situ into a chitosan (CS) matrix to obtain highly dispersed antibacterial composites by the sol–gel technique. These composites were characterized by their thermal, structural, morphological and optical properties. NPs were subsequently used and added into polyvinyl alcohol (PVA) in order to obtain electrospun fibers. Previously, it was determined the adequate PVA/CS ratio and changes in their morphological features in dependence of molecular weight of PVA and electrospinning parameters to avoid the beads and spindle-like defects in the final fibers. Then, optimal conditions were used to fabricate PVA/in situ ZnO:CS nanofiber composites. The hydrogen bonding interaction governs the ZnO:CS system, which forms a combination between flower-type and agglomerated rod morphologies. It was found that CS promotes the crystallinity of ZnO NPs maintaining the hexagonal phase. The addition of ZnO into the CS matrix was performed via weak interactions by stabilizing the hybrid compound after the second decomposition stage when the mass loss is above 50%. Free-defects uniform fibers with an improvement in hardness as well as in the elastic modulus was obtained in the electrospun PVA/in situ ZnO:CS fibers. The presence of ZnO NPs improves the spinnability in the fiber nanocomposites with an average diameter of 223 nm. PVA/in situ ZnO:CS mats displayed an inhibition of bacterial growth of Escherichia coli and Staphylococcus aureus.

The quantitative estimation of strengthening mechanisms of rails’ surface layer is carried out on the basis of regularities and formation mechanisms of structure-phase states revealed by the methods of modern physical materials science. It is performed at different depth of rail head along central axis and fillet of differentially quenched 100-m rails after extremely long-term operation (gross passed tonnage of 1411 mln. tons). The contributions caused by the matrix lattice friction, intraphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution strengthening of pearlite component of steel structure were estimated. It is shown that in the surface layer the main mechanism of strengthening is due to the interaction of moving dislocations with low-angle boundaries of nanometer dimensional fragments and subgrains. In a near-surface layer at a depth of 2–10 mm the main dislocation strengthening mechanism is due to interaction of moving dislocations with immobile ones.

Mine surveying in mining operations is of particular importance, since all technological processes of the full life cycle of a mining enterprise and, ultimately, its competitiveness depend on the surveying quality, efficiency and reliability. Organizations independently determine the structure of mine surveying services, taking into account the methods applied and the scale of mining. To ensure safe open-pit mining of minerals, it is necessary to permanently assess and monitor the pit bench and wall rock mass condition. Misjudgement of rock physical and mechanical properties, non-observance of the minerals mining and transportation process cycle, changes in climatic conditions and other problems lead to loss of stability of rocks in all parts of an open pit, including in the areas of ore production and mining and transport equipment operation. The existing practice shows that the effectiveness of an open pit wall and bench stability calculation can be achieved using a technique that should take into account the slope deformation and failure mechanism, as well as the nature of the stress-strain state of the open pit rock mass. The studies presented in the paper are based on comparative analysis of the sliding wedge parameters for benches, dumps and roads at open pits using analytical and graphical software packages, and taking into account the static load produced by dump trucks. The study findings allow to establish that: determination of the bench slope stability and the sliding wedge width, performed by the analytical method, gives higher accuracy results than those obtained by the graphical method; the bench slope stability and the sliding wedge width depend not only on the rock physical and mechanical condition, but also on the bench height, the dump truck (plus its freight load) weight per 1 linear meter of the placement area, the distance from the slope edge and other factors; the rock mass is stable and not subject to landslide phenomena for as long as the sum of the holding forces is greater than or equal to the sum of the shearing forces; when using large-sized transport equipment of nonstandard weight in open-pit mining, it is necessary to calculate the safe width of the sliding wedges, taking into account the loads on them (per 1 linear meter), the values of which can be 1.5–2.0 times higher than those calculated for the circular-cylindrical sliding surface.

The influence of different Mg concentrations on the mechanical properties and microstructure of an Al–Li alloy was studied. The highest Mg content was up to 1.1 wt.%. To the best of the authors knowledge, alloys with such a high Mg content has not been reported in the literature. The mechanical properties, yield strength and elongation at failure, of all of the alloys were investigated by tensile tests. Characterisation of the precipitates by analysing the dark field images and related diffraction patterns revealed that precipitation of the T1 phase (Al2CuLi) was retarded by high (1.1 wt.%) Mg concentration. We hypothesized that a competition between the precipitation of T1 phase and S' phase in high Mg containing alloy caused sluggish precipitation phenomenon and associated strengthening.

Lead-free halide double perovskite materials have the advantages of optical absorption efficiency, carrier mobility, adjustable bandgap, defect tolerance, wide variety of raw materials, low price, etc. which were used as many environmental substitutes for lead-based halide perovskite materials. In this work, we investigated the Cs2NaSbX6 (X = Cl, Br, I) systems with elements (K, In and Au) alloying and the photoelectric properties of the materials with the first principle method. The research results show that when the alloying concentration was 50%, all bandgaps of given double perovskite materials turned from indirect to direct bandgap. Especially, the alloying Cs2Na0.5K0.5SbI6's and the Cs2NaSb0.5In0.5I6's bandgaps were 1.92eVand 1.46eV, respectively. The energy values are well match within the range of applications as light absorbing materials. Optical properties show that the peak position of the absorption spectrum of the alloying elements of the Cs2NaSbX6 (X = Cl, Br, I) system is associated with the types of halogen elements at the X site, for X = Cl element, alloying elements to a certain proportion makes the absorption spectrum of the material red shift; for X = Br, There is no obvious change in the position of the peak of the absorption spectrum of the material; for X = I, after alloying elements to a certain proportion, the position of the peak of the absorption spectrum of the material has an obvious blueshifts. This work provides a reliable theoretical basis for the bandgap regulation of perovskite materials and a reference for the development of new non-toxic and environmentally friendly solar materials.

The effect of an electric field with different polarities on the inner wall of a submerged entry nozzle made of rare earth steel was investigated. The results show that the electric field induces a change in the decarburization, erosion, and clogging processes of the nozzle. In the casting of rare earth steel, the negative electric field affects the decarburization, erosion, and clogging of the nozzle. Moreover, when a reverse positive electric field is applied on the wall of the submerged entry nozzle, these processes can be effectively reduced. This ensures the integrity of the submerged entry nozzle and its smooth production during the continuous casting process.

The paper is devoted to the urgent problem of sustainable and economically secure development of enterprises in the Tver Region peat-extracting sector of the economy. Despite the fact that peat deposits are widespread in many regions of Russia, the efficiency of their industrial and economic use is extremely low. The purpose of the study was to determine the features of the assessment and analysis of the economic security of an enterprise that develops peat deposits. The paper examines the relationship between the concepts of “peat rent” and “economic security”, and also provides the author’s interpretation of their content and essence. An analysis of the existing approaches to assessing the economic security of peat extracting enterprises was carried out, and the use of the rent approach was substantiated based on the data on the peat industry enterprises used in this study. The indicators for assessing the economic security of a peat production were identified. The authors proposed a methodological approach, a feature of which was comprehensive accounting of technical, economic, and natural factors that objectively affected the level of economic security of peat extracting enterprises. The proposed methodological approach also makes it possible to develop recommendations for increasing the flexibility and adaptability of peat extracting enterprises, taking into account the individual conditions of their work. The methodological research toolkit included the fundamentals of economic theory, information methods for processing statistical data, and economic and mathematical modeling. The methodology approbation was carried out through the example of enterprises of the Tver Region peat-extracting industry, which had been at a low ebb (in protracted economic crisis) for a long time. The conclusions, recommendations, and proposals of the study were used in the development of the Regional program “Natural Resources Management and Environmental Protection” for 2017–2022 (Order of the Tver Region Government No. 414-pp of December 26, 2016 as amended on February 7, 2020).

Continuous TiNb fiber reinforced TiAl composites (TiNbf/TiAl) have tremendous potential for substituting brittle TiAl alloy to service on advanced aerospace equipment. This study has clarified microstructure evolution of TiNbf/TiAl composites and successfully achieved the structure modification of TiNb fiber by aging process where strengthening phase α-Ti could precipitate homogeneously in basket shape at the core of fiber meanwhile the formation and growth of brittle O phase could be effectively inhibited. Through aging process, both strength and toughness of composites have achieved a remarkable enhancement. Tensile fracture strength and strain of composites were significantly improved by 87% and 74% respectively compared with TiAl matrix. The K1C reflecting the toughness was enhanced nearly doubled benefit from multiple interaction mechanisms. The compressive strength of composites at 700 °C can reach 1078 MPa which still reached up to 847 MPa at 800 °C. The micromechanical properties of each phase were investigated systematically to reveal the strengthening and toughening mechanism. The growth behavior and the stability of interface structure were also involved with first-principles method.

The effect of Al content on the high-temperature oxidation (800 and 900 °C) of 18Cr–Al–Si FHSS (ferritic heat-resistant stainless steel) for up to 180 h in air was investigated via the isothermal oxidation method. The oxidation kinetic curves followed a parabolic law. A higher Al content reduced the oxidation rate and improved the oxidation resistance and also promoted the formation of a denser and more continuous Al2O3 film during the early oxidation stages, which provided an effective barrier that hindered the diffusion of oxygen into the matrix. The oxide films that formed on the 0.63Al FHSS and 1.06Al FHSS were composed of spinel MnCr2O4 in the outer layer, MnO and Cr2O3 in the middle layer, and Al2O3 and SiO2 in the inner layer. The middle layer of 0.63Al FHSS also contained a small amount of Fe2O3. The oxidation mechanism was also discussed based on oxidation kinetics, morphological observations, and phase analysis of oxide films.

The effects of rare earth (RE) addition on the corrosion behavior of micro-alloyed steels in 3.5 wt.% NaCl solution were investigated elaborately through electrochemical tests and material characterization analyses. Results showed that the corrosion rate decreased after addition of RE elements. The RE elements did not alter the pitting nucleation mechanism, while the sensitivity of pitting propagation was reduced by decreasing the pitting density and pitting depth. In the long-term corrosion, preferential precipitation of RE corrosion products promoted the formation of protective rust layers and accelerated the co-deposition of these layers, which probably be favorable for the formation of compact rust layers. Moreover, the RE addition reduced the surface electrochemical activity and the adsorption tendency of Cl− on the metal surface. As a consequence, the resistance of electrochemical reactions (represented by Rp values in EIS tests) increased, resulting in a decrease of corrosion rate by RE addition.