Chemical Composition Of Alloy Research Articles

Corrosion of Anodized Titanium Alloys

Ti and Ti alloys are employed in demanding industries such as aerospace, automotive, biomedical, aeronautic, structural, naval, and chemical, thanks to their resistance to corrosion due to the formation of the TiO2 film on the surface. Diverse research has established that different corrosive media could attack the oxide layer. One way to generate a stable, compact, and continuous oxide film is through anodizing treatment. The efficiency of anodization depends on diverse factors such as the microstructure, chemical composition of alloys, pH of electrolyte, time, and temperature of anodizing. This review aims to examine the corrosion resistance of the anodized layer on Ti and Ti alloys, with different parameters. The discussion is centered on the influence of the different parameters and alloy properties in the effectivity of anodizing when they are characterized by electrochemical techniques while studying the behavior of oxide.

The efficiency of thermal protection of ICE pistons with the micro-arc oxidation

BACKGROUND: In order to protect pistons of internal combustion engines (ICE) from burnout and increase their durability, it is reasonable to use ceramic coatings formed on the piston head with micro-arc oxidation (MAO). Many scientific papers have been devoted to the study of the efficiency of these coatings. However, most of these studies were carried out at laboratory facilities simulating the engine operation, generally, not taking into account the real thermophysical parameters of the MAO coating. Therefore, the thermal protection efficiency of these coatings is difficult to assess. AIM: Study of efficiency of the thermal protection of pistons using a ceramic coating formed by micro-arc oxidation on the piston head with numerical simulation. METHODS: The study was conducted in the SolidWorks Simulation software. Two piston aluminum alloys were used as the piston material: AK12d (with a silicon content of 12%) and AK4-1 (with a silicon content of 0.35%). Temperature loads corresponding to the operation of a real engine were applied to the surfaces of the model piston. At the first stage of the study, the thermal state of pistons made of different uncoated alloys was simulated. At the second and third stages of the study, the effect of the coating thickness on the piston thermal state was simulated. The piston material of the second study stage was the AK4-1 alloy. The piston material of the third study stage was the AK12d alloy. Ceramics, which properties correspond to the coatings properties formed with the micro-arc oxidation method on these alloys, were used as the coating material. The coating thickness varied in the range from 50 to 350 µm in increments of 100 µm. The probing method was used to determine the temperature in various areas of the piston, such as at the piston head surface at the MAO coating and under it, in the area of piston grooves, at a piston skirt and the piston head from the side of a crankcase. RESULTS: With the simulation, it was found that: The micro-arc coating of the piston head reduces the thermal tension of the piston regardless of the aluminum alloy chemical composition. The efficiency of the piston’s thermal protection increases with an increase in the ceramic coating thickness and a decrease in its thermal conductivity coefficient. The greatest heat-protecting effect is achieved by the piston made of the AK12d eutectic alloy. CONCLUSIONS: It is found that the MAO coating at the piston head is an effective way to reduce the thermal tension of the ICE pistons. Increasing the ceramic coating thickness and a decrease in its thermal conductivity coefficient increases the efficiency of the pistons thermal protection. Reducing the thermal conductivity of the MAO coating and increasing the MAO coating thickness increases the temperature on the coating surface.

Corrosion Behavior of Aluminum Alloys in Different Alkaline Environments: Effect of Alloying Elements and Anodization Treatments

Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline solutions (i.e., pH and presence of chlorides) on the corrosion resistance of three aluminum alloys (AA 5083-H111, AA 6082-T6, and AA 7075-T6) with and without anodizing treatments. Open circuit potential (EOCP) and anodic polarization measurements were carried out and typical corrosion parameters such as corrosion current density (icor) and corrosion rate (CR) were determined. Morphology of the corrosion attack and samples microstructure were investigated by scanning electron microscope. Results show that corrosion behavior of the three investigated alloys is influenced by (i) the aggressiveness of the testing environments; (ii) the thickness of the anodizing treatment; (iii) the alloy chemical composition; (iv) the distribution of intermetallic phases in the aluminum matrix. Moreover, three galvanic series have been built also testing other metallic alloys commonly used in mechanical applications, i.e., carbon steel (C40), stainless-steel (AISI 304), and Cu-based alloys (Cu-Ni alloy and CW 617 N, respectively). Results clearly indicate that galvanic series play a fundamental role when it is necessary to select an alloy for a specific environment, highlighting the thermodynamic conditions for corrosion occurrence. On the other hand, kinetic measurements and microstructural studies carried out on the three aluminum alloys stress the importance of the surface treatments and relevant thickness as well as the effect of metal exposure. Future work will involve the study of other surface treatments on aluminum alloys and the evaluation of their corrosion behavior in acidic environments.

Exfoliation of an extruded Mg-4Li-1Ca alloy in presence of glucose and bovine serum albumin

Exfoliation corrosion (EFC) on extruded Mg-4Li-1Ca alloys as bone implant materials has not been reported. This study aimed to elucidate the degradation mechanism of a corrosion type-exfoliation occurred on an extruded Mg-4Li-1Ca alloy under the interaction of glucose (Glu) and bovine serum albumin (BSA) in Hank’s solution. The alloy microstructure, chemical composition, texture, stress distribution and Volta potential maps were characterized using metallographic microscopy, scanning electron microscopy and electron backscattered diffraction, and scanning Kelvin Probe. The alloy corrosion behavior was investigated via electrochemical testing and hydrogen evolution rate methods. X-ray diffraction, Fourier transform infrared spectrometry, X-ray photoelectron spectrometer, and fluorescence microscopy were used to analyze the corrosion products and the adsorption of the organic molecules. The experimental results indicated that the anodic second phase (Mg2Ca) were distributed in lamellar and rod-like patterns along the extrusion direction of the alloy, a lower Volta potential for Mg2Ca, texture and residual stresses also promote EFC. An increase in Glu concentration exacerbated the EFC, whereas BSA inhibited the EFC of the alloy. Higher Glu concentrations in BSA in turn inhibited EFC since Glu can complex with amino acids in proteins to form Glu-amino acid amides, which promoted protein adsorption and thereby forming a dense protective film on the alloy surface. The preferential dissolution of the Mg2Ca phase particles led to the complexation and adsorption of Glu and protein. This study enriches the understanding of the corrosion types in biomedical Mg-4Li-1Ca alloy and paving the way for enhancing the EFC resistance of the alloy.

Corrosion Properties of Quenching and Partitioning-Processed Martensitic Stainless Steels

The increasing demand for lightweight and energy-efficient automobile materials has prompted consideration of the Quenching and Partitioning (Q&P) process for developing martensitic stainless steels with enhanced combinations of strength and ductility. The microstructures of Q&P-processed martensitic stainless steels primarily consist of a matrix of carbon-depleted martensite and films of retained austenite, although some high-carbon fresh martensite may be present.This research aimed to elucidate the influence of chemical composition (manganese content), heat treatment, and phase fractions (martensite and retained austenite) on the corrosion properties of Q&P-processed martensitic stainless steels.The microstructures were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). Corrosion properties were evaluated through electrochemical measurements in a 3.5% NaCl solution, which included open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Scanning Kelvin probe force microscopy (SKPFM) measurements were also conducted.Q&P process ideally minimizes carbide formation, as all carbon atoms are partitioned into austenite. Nevertheless, our research demonstrates that this condition is not always met. Depending on the alloy's chemical composition and the partitioning temperature, carbides and inclusions may still form, favoring localized corrosion such as pitting and intergranular corrosion.

Structural and mechanical properties of the additive manufactured CrFeCoNi(Al,Ti) high-entropy alloys produced using powder blends

High-entropy Alloys (HEAs) are considered prospective materials demonstrating the new approach of alloy design creating new compositions for harsh conditions. However, searching for alloy chemical composition providing the best material properties is a costly process. Additive manufacturing (AM) can be an effective technique for adjusting the alloy composition by using several initial materials. The powder bed fusion (PBF) AM process allows the printing of solid parts using powder blends. In the present study, the CrFeCoNi(Al,Ti) HEAs were printed by the PBF technique using the blends of three powders. The structural and phase investigations revealed the chemical inhomogeneity in the materials that led to the new phase formations affecting the mechanical characteristics. The high-temperature annealing at 1200 °C can be considered a post-treatment process for the printed alloys as a homogenization process while the annealing at a lower temperature of 800 °C initiates the decomposition of the initially formed f.c.c. phase.

Prediction Modeling of Low Alloy Steel Based on Chemical Composition and Heat Treatment Using Artificial Neural Network

The utilization of machine learning methods in modern material science enables the design of more efficient and innovative materials. This research aims to develop a machine learning model using the Artificial Neural Network (ANN) algorithm to predict the mechanical properties of low alloy steel. The dataset used consists of 15 input variables and 2 output variables, namely Yield Strength (YS) and Tensile Strength (TS). In this study, three ANN architectures were designed and their performance was compared using evaluation metrics such as Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and R-squared. During the search for the best parameters for the ANN model, variations were made in the optimizer, learning rate, and batch size. The evaluation was conducted using cross-validation technique with k=10. The evaluation results indicate that the model with the best performance in predicting YS had MAE of 18.197, RMSE of 23.552, and R-squared of 0.969. For predicting TS, the model achieved MAE of 27, RMSE of 36.696, and R-squared of 0.907. The research results demonstrate that the ANN model can be used to predict the mechanical properties of low alloy steel based on alloy chemical composition and heat treatment temperature with reasonably high accuracy

FEM Numerical and Experimental Work on Extrusion Welding of 7021 Aluminum Alloy.

Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures-400, 450 and 500 °C-and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature-pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96-101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature-speed conditions of deformation.

Machine learning interphase precipitation behavior of Ti micro-alloyed steel guided by physical metallurgy principle

Nano-sized interphase precipitates, which form in ordered rows, are critical for high strength low alloy (HSLA) steels, in achieving the desired strength needed for downgauging for light-weighting automotive structures. The occurrence of interphase precipitation depends on many interrelated parameters, such as alloy chemical composition, temperature, processing parameters and crystallography. In this paper, we use data analysis based on machine learning algorithm: decision tree to predict whether interphase precipitation can occur. Due to the high strength of interphase precipitation and the minimum alloy content is one of the important goals pursued of iron and steel enterprises. Therefore, under the condition that interphase precipitation occurs, the chemical composition of the alloy can be reduced by using interphase precipitation. Guided by the physical metallurgy principle, this paper transforms the processing parameters into physical metallurgy parameters such as grain size, stored deformation energy, ferrite phase transformation temperature, and decision tree (DT) algorithm was used to model and verify whether interphase precipitation can occur. Under the condition of interphase precipitation, the support vector machine (SVM) models of interphase precipitation characteristic values were established. Based on the DT model and the SVM model, the particle swarm optimization (PSO) algorithm was used for the reduction design of the alloy, and the chemical composition can be reduced according to the target strengthening strength. The results of alloy reduction have been verified by experiments, which shows that the alloy can be reduced by using interphase precipitation.

THE IMPLEMENTATION OF PANDAS PROFILING AS A TOOL FOR ANALYZING MECHANICAL PROPERTIES DATA OF NICKEL-BASED SUPERALLOYS BASED ON ALLOY CHEMICAL COMPOSITION

The purpose of this study is to evaluate the mechanical properties of nickel-based superalloys with variations in alloy chemical compositions using the Exploratory Data Analysis (EDA) method with the assistance of the pandas profiling library on Google Colab. In this study, data from 312 tensile tests of nickel-based superalloys were used as research samples, with alloy chemical compositions including carbon (C), manganese (Mn), silicon (Si), chromium (Cr), nickel (Ni), molybdenum (Mo), vanadium (V), nitrogen (N), niobium (Nb), cobalt (Co), tungsten (W), aluminum (Al), and titanium (Ti), as well as mechanical properties such as yield strength (YS), tensile strength (TS), and elongation (EL). The methodology used in this study was the EDA method with the assistance of the pandas profiling library on Google Colab, which enables the automatic creation of a dataset report, presenting information on various aspects such as data structure, descriptive statistics, correlation, distribution, and missing values. The results show that yield strength has a fairly high correlation with titanium (0.51), medium correlations with nickel (0.25), vanadium (0.2), and cobalt (0.2). Tensile strength in nickel-based superalloys has a fairly high correlation with yield strength (0.88), carbon (0.49), and cobalt (0.55), and medium correlations with titanium (0.25) and vanadium (0.25). Elongation in nickel-based superalloys has a negative and fairly high correlation with tensile strength (-0.62) and yield strength (-0.58). Some warnings for missing data and zero values in some variables were identified. These results indicate that the pandas profiling library can be used as a tool to analyze the data of mechanical properties of nickel-based superalloys quickly and easily, and provide clear information on data patterns, data structure, and correlation among data.

Role of ZnO/MWCNTs hybrids nanoparticles addition on the tribological behaviour of SN150 paraffinic mineral oil

AbstractNanoparticle incorporation plays an active feature in heat transfer, ultimately enhancing the tribological process under boundary conditions of heat stress. Nanoparticles like zinc oxide (ZnO) and multiwall carbon nanotubes (MWCNT) are well known to significantly affect the cooling and lubrication applications, resulting in improved heat transfer and kinematic viscosity. The present work investigates the tribological performance of ZnO/MWCNTs hybrids as lubricant additive in the paraffinic type of mineral base oil of Group I (SN150) engine oil. The chemical composition of the modified and unmodified oil was examined by an inductively coupled plasma‐optical emission spectrometer (ICP‐OES), energy dispersive x‐ray fluorescence (EDXRF) spectrometer, and Fourier‐transform infrared spectroscopy (FTIR). A ring‐on‐disk tribotester was performed to investigate the tribological behaviour through the linear reciprocating mechanism alloy‐steel contacts. The worn steel alloy surfaces morphology and chemical compositions were examined by scanning electron microscope (SEM), energy‐dispersive x‐ray spectroscopy (EDX), and 3D optical profilometer. Different ZnO/MWCNTs nanomaterial volumetric concentrations were examined in order to determine the most effective performance. According to the tribological results, ZnO/MWCNTs hybrid nanomaterials in the engine oil were found to have significantly higher friction temperature and antiwear capability than the base oil. A volumetric concentration of 3.00 wt% ZnO/MWCNTs nanomaterials to SN150 engine oil imparted excellent wear protection to the steel sample than the pure SN150 base oil. Based on the statistical analysis, the modified oil anti‐wear performance was enhanced by reducing the wear loss by 80.5% and friction temperature by 55.8°C compared with the oil base.

Mechanical Properties Enhancement of Biomedical Au–Cu–Al Shape Memory Alloys by Phase Manipulation

β-type Au-Cu-Al alloy, which is known as Spangold, has been developed for biomedical applications due to its high biocompatibility and X-ray contrast. Despite that, the workability of the polycrystalline functional phases (i.e., L21 parent and martensite phases) is limited by grain boundary embrittlement. To enhance the mechanical properties of the martensite phase (M-phase) alloy, this study aims to introduce a ductile α-fcc phase with various fractions into the M-phase alloy by manipulating the alloy chemical composition. Fundamental analysis such as phase identifications, thermal analysis, microstructure observations, and tensile tests were performed. As a result, the dual-phase M+α-fcc alloys with varying α-fcc phase fractions were successfully practiced. Among all alloys, their lattice parameters and phase transformation temperatures showed merely slight alteration, suggesting that the chemical compositions of the functional M-phases are similar for all alloys. Hence, the variations in the mechanical properties mainly originate from the different α-fcc phase fractions. The tensile test results indicate that both the ultimate tensile strength and fracture strain are promoted as the α-fcc phase fraction increases. The 50Au-38Cu-12Al alloy with the highest α-fcc phase fraction performs the most optimized mechanical properties.

Surface composition, structure and corrosion properties of a ZrTiNb alloy: Effect of impact treatment energy

A comparative study of the microstructure, surface chemical and phase composition, microtopography, surface roughness, microhardness, and corrosion properties of Zr31Ti18Nb alloy in as-prepared state and after ultrasonic impact treatment under two loading schemes has been carried out by using XRD, XPS, SEM/EDX and TEM/SAED. The surface of as-prepared alloy was considerably enriched with Zr as compared to the nominal composition, covered by a thick native oxide and comprised carbide and nitride precipitates. The processing of the alloy for 2 min in (i) a multi-pin impacting mode combined with a reciprocating movement of the sample and (ii) single-pin normal impacting mode caused deformation-enhanced uptake of oxygen promoting further oxidation of the alloy components. Besides, the impact treatment brought about the accumulation of structural defects, texturing, generation of compressive residual stresses, a decrease in surface roughness, an increase in microhardness, and a significant increase in the corrosion resistance of the alloy in a 0.9% NaCl solution. The highest effect of surface modification of the alloy was obtained after treatment in the single-pin impacting mode. This was related to a larger energy density and power density deposited in the impact area during processing in this mode as evaluated from measurements of pins’ energetics.

Combining physical vapor deposition structuration with dealloying for the creation of a highly efficient SERS platform.

Nanostructured noble metal thin films are highly studied for their interesting plasmonic properties. The latter can be effectively used for the detection of small and highly diluted molecules by the surface-enhanced Raman scattering (SERS) effect. Regardless of impressive detection limits achieved, synthesis complexity and the high cost of gold restrict its use in devices. Here, we report on a novel two-step approach that combines the deposition of a silver-aluminum thin film with dealloying to design and fabricate efficient SERS platforms. The magnetron sputtering technique was used for the deposition of the alloy thin film to be dealloyed. After dealloying, the resulting silver nanoporous structures revealed two degrees of porosity: macroporosity, associated to the initial alloy morphology, and nanoporosity, related to the dealloying step. The resulting nanoporous columnar structure was finely optimized by tuning deposition (i.e., the alloy chemical composition) and dealloying (i.e., dealloying media) parameters to reach the best SERS properties. These are reported for samples dealloyed in HCl and with 30 atom % of silver at the initial state with a detection limit down to 10-10 mol·L-1 for a solution of rhodamine B.

Bespoke multi-step homogenization heat-treatment for a laser powder bed fused AlSi10Mg4Cu alloy synthesized via in-situ alloying

Although in-situ alloying is a flourishing technique for developing novel metal alloys for Laser Powder Bed Fusion (LPBF), the mixed alloying elements regularly segregate, causing a heterogeneous chemical composition enriched with new metastable phases. Hence, the present study focuses on the homogenization of an in-situ alloyed AlSi10Mg4Cu metal system by pursuing various heat-treatment pathways. We firstly investigated the alloy homogenization behavior upon conducting single-step heat-treatments at 485, 500, and 515 °C for set times. Experimental findings revealed that the alloy was challenging to homogenize in one-go. Heat-treating at 485 °C did not enable the complete dissolution of Cu-rich phases. By increasing temperature at 500 °C, the alloy was neither homogenized nor near-fully dense due to the untimely incipient melting of metastable Q-Al 4 Cu 2 Mg 8 Si 7 phase which caused pores. Lastly, homogenization at 515 °C led to the enhanced dissolution of θ -Al 2 Cu phase and its precursors but simultaneously exacerbated the incipient melting process of Q-Al 4 Cu 2 Mg 8 Si 7 phase observed at 500 °C. Based on the analyses of single-step homogenization behaviors, we designed a multi-step homogenization heat-treatment to dissolve the low-melting Q- phase selectively avoiding its deleterious incipient melting. The material underwent then a homogenization treatment with three consecutives steps at 495 °C for 4 h, 505 °C for 6 h and 515 °C for 6 h. The homogenization response was satisfying this time: incipient melting of Q-Al 4 Cu 2 Mg 8 Si 7 phase was annihilated, and Cu solubilization was greatly enhanced. The supersaturation level was comparable with that of the as-built condition, i.e., optimal for following age-hardening treatments. • AlSi10Mg + 4Cu alloy is produced by LPBF in-situ alloying. • Various heat-treatment pathways are investigated to homogenize the alloy chemical composition. • Single-step homogenization at 485 °C did not entirely dissolve θ -Al 2 Cu phase; • Single-step homogenization at 500 °C partially solubilized θ - phase but induced early-stage incipient melting of Q-Al 4 Cu 2 Mg 8 Si 7 phase; • Single-step homogenization conducted at 515 °C dissolved θ -Al 2 Cu while causing incipient melting of Q- phase; • Multi-step homogenization solubilized Cu segregations avoiding incipient melting of Q- phase.

A Comprehensive Investigation on the Effects of Surface Finishing on the Resistance of Stainless Steel to Localized Corrosion

The present research investigates the influence of surface roughness imparted by cold surface finishing processes on the localized corrosion resistance of stainless steel. Five different alloys were studied: ferritic AISI 430, martensitic AISI 430F, austenitic AISI 303, AISI 304L, and AISI 316L. It was demonstrated that the grinding process, executed on previously cold drawn bars, leads to an improvement in corrosion resistance according to the results obtained with electrochemical tests, namely, potentiostatic and potentiodynamic tests in chloride-rich environments, the salt spray test, and long-term exposure in urban and marine atmospheres. This allowed us to establish a trend among the different alloys regarding the resistance to pitting corrosion, which was assessed according to pitting potentials, critical chloride contents, and pitting initiation time. All the tests confirmed that surface finishing, as well as alloy chemical composition, is an important factor in controlling the corrosion resistance of stainless steel.

Effect of composition and heat treatment on the mechanical properties of Fe Mn Al steels

Starting from the research aimed at the development of substitute alloys for stainless steels, with the aim of replacing strategic metals such as chromium and nickel with the more available manganese, FeMnAlC alloys have been studied and developed for several years. These alloys exhibit an attractive strength/ductility combination, low density, and some of them show good oxidation behaviour at high temperatures. After a preliminary study, in this paper the effect of a solubilization treatment followed by aging in the temperature range 550 - 750 °C has been evaluated. The results of the investigation revealed that the steel characterized by the higher amount of Mn and Al shows, after heat treatment, the formation of phases that make the alloy very brittle. Considering the obtained results, it is evident that optimizing the alloy chemical composition is of paramount importance to guarantee a high fracture toughness if the steel works for limited time intervals at high temperature.

Discussion on the presence condition of suboxide ZrO beneath the oxide in zirconium alloys

Characteristics related to the oxide-metal interface of oxidized (corroded) zirconium alloys in an autoclave have been extensively explored using both experimental and theoretical methods during the last ten years. A thin intermediate or suboxide layer with an approximate 1:1 ZrO stoichiometry was observed at the oxide-metal interface in several zirconium alloys. Through investigating its chemical composition, morphology, grain size and orientation relationship with the substrate α-Zr, some researchers assumed that the suboxide layer is related to the oxidation (corrosion) rate, whereas others did not. The majority of earlier studies used aqueous corrosion samples that were exposed to high pressure and low temperature, simulating in-service conditions. However, the interfacial characteristics at higher temperature have been scarcely reported. In this study, we focused on the microstructure and micro-chemistry of the oxide and suboxide ZrO in Zircaloy-4 and Zr-1.0Nb-0.01Cu oxidized at 650–1000 °C by combining Backscattered Electron (BSE) mode in Scanning Electron Microscope (SEM), Transmission Electron Backscatter Diffraction (t-EBSD) and (Scanning) Transmission Electron Microscope fitted with an Energy Dispersive X-ray Spectroscope ((S)TEM-EDS). The results show that the suboxide ZrO in oxidized Zircaloy-4 and Zr-1.0Nb-0.01Cu alloys has different morphologies. With increasing oxidation temperature, the suboxide ZrO distribution varies significantly, from a continuous layer to a few occasional blocky grains, until any ZrO grains are undetectable at the ZrO2/α-Zr(O) interface. The hexagonal crystallographic structure of ZrO has also been confirmed. According to discussions combining our investigations and earlier reports, the presence of suboxide ZrO and their morphology are probably related to the oxidation temperature, chemical composition of alloys and complex stress accumulation adjacent to the interfacial region.

Influence of minor Zn additions on grain boundary anelasticity, grain boundary sliding, and superplasticity of Al-Mg-based alloys

Al-Mg alloys (AA5083-type) are widely used for superplastic forming. Limited grain boundary sliding as compared to other superplastic alloys limits the formability of Al-Mg based alloys. Grain boundary sliding intensity depends on the grain size, grain boundaries structure, and chemical composition of alloys. To improve superplastic properties of Al-Mg based alloys, we investigated the influence of a minor addition of Zn on the grain boundary relaxation effect and grain boundary sliding ability. The temperature dependence internal friction, superplastic deformation behavior, and microstructural changes during superplastic deformation for the AA5083 alloy and Zn modified alloy were compared. A minor Zn addition of 0.7 wt% does not influence the mean grain size but decreases the relaxation strength and the activation energy of grain boundary relaxation. The mechanisms of superplastic deformation and their contributions to the total strain were analyzed using FIB-milled grids evolution on the samples’ surface. Grain boundary sliding, grain rotations, and intragranular strain included both dislocation slip/creep and diffusional creep were involved in the deformation process. The contribution of grain boundary sliding increased from 10% to 25% for the Zn-free AA5083 alloy to 30–50% for the Zn-modified alloy. In result, a minor Zn addition proved to stimulate grain boundary sliding that decreases stress and increases strain rate sensitivity and elongation-to-failure of the studied alloy.

Development of new composition for sHSS steel used for hot rolling mill rolls at Magnitogorsk Iron and Steel Works

The paper presents the results of the complex scientific and research work directed on development of the new composition of sHSS steel for rolling mill rolls together with Magnito-gorsk Iron and Steel Works (MMK) and Magnitogorsk Mill Rolls Plant (MZPV). The first part includes the review of technical literature in the field of the results of roll steel examination by domestic and foreign researchers, investigation of structure and determination of properties of foreign rolling rolls, which were operated at the MMK hot rolling mill. The minimal level od sHSS steel properties for the working layer of a rolling roll, providing its operation reliability, is also determined. Laboratorial experiments were conducted at the second stage. The formed massif of ex-perimental data was processed using neural net, and as a result, the optimal chemical composition of the roll steel with high wear resistance and hardness was obtained. After processing of the re-sults of the planned experiment, the regression equation was obtained; it describes influence of the alloy chemical composition on wear resistance and hardness coefficients. Optimized composition of the alloy was developed at Magnitogorsk Mill Rolls Plant; it wad resulted in manufacture of the pilot roll sleeve in centrifugal machine. This roll sleeve was subjected to heat treatment according to the standard plant procedure. The final step included laboratorial testing of the pilot roll sleeve which was manufac-tured from steel with optimized chemical composition. It was determined that the developed composition is characterized by wear resistance increased by 27 % in comparison with the re-searched foreign analogue, as well as by similar qualitative parameters of the alloy microstructure.