Content Of Alloying Elements Research Articles

Correlation of structure parameters and performance characteristics of alloy steels for shipbuilding

The article presents the results of a study of the relationship between strength and performance (temperatures of ductile-brittle transition Tdb and zero plasticity NDT, critical opening at the crack tip CTOD at a test temperature of —40°C) on the structure parameters of thick plate products made of low-carbon low-alloy steels with different contents of basic alloying and microalloying elements.

Nanocrystallization of a Ti40 cladding layer by ultrasonic impact to improve burn resistance

With the wide application of titanium alloys in the aerospace industry, the burn resistance properties and surface strengthening processes of titanium alloys have been received increasing attention. In this study, Ti40 burn-resistant titanium alloy was cladded on the surface of TC4 by electron beam cladding, and the surface layer of the nanostructure was prepared by ultrasonic impact treatment (UIT). The nanostructure layer was examined by pulse laser ablation. The results showed that when the moving speed was 16 mm/s, the maximum thickness of the plastic deformation zone of the UIT Ti40 cladding layer reached 150 μm. The highest hardness value was 531 HV, which was approximately 43.5% higher than the original microstructure of the Ti40 cladding layer without UIT. Moreover, the surface microstructure of the Ti40 burn resistant titanium alloy cladding layer was nanocrystalline with uniform distribution and random orientation, and the average grain size was 50 nm. The UIT process can effectively increase the relative content of burn-resistant alloy elements on the surface of the Ti40 cladding layer and increase the content of dense oxidation protective films after laser ablation, which hinders the diffusion and migration of oxygen elements to the matrix alloy in the process of ablation and then improves the burn resistance of the Ti40 cladding layer.

Thermodynamic Calculation and Characterization of Carbide Precipitation in Laser-Deposited Material for High-Speed Steel Alloy

The laser cladding of the T15 high-speed steel (HSS) was accomplished and its typical microstructure was determined. The microstructure characterization of the clad layer showed three phases of microstructure, planar, cellular and equiaxed growth zones. Electron probe micro-analyzer (EPMA) showed high content in alloying elements at the cellular and equiaxed zones that contained V, C, Cr and W. Further, the analysis at the inter-granular zone presented the highest concentration in elements such as Mo, Cr and W. This showed the presence of carbides which were identified as MCI and M6C at the cellular zone, and M7C3 and M23C6 at the equiaxed and inter-granular zones. The precipitation characterization along the line starting from the substrate and passing through the clad layer identified the austenite matrix and revealed the fluctuation in the alloying elements content, where its amplitude and count increased while passing through the planar zone and hitting the equiaxed zone. Equilibrium phase diagram thermodynamic calculation proved the presence of MCI, M6C and M23C6 which precipitated respectively as the solidification proceeded. The M6C carbide was rich in Fe and W with the presence of V and Cr. MCI carbide had high content of C and V also with dissolved content of W and Cr. Finally, M23C6 carbide contained high amounts of W, Cr and Mo. Scheil–Gulliver simulation model showed the presence of M6C and MCI similar to the equilibrium phase diagram results, additionally, two carbides were revealed and identified as M7C3 and MCII carbides. The M23C6 was absent from the Scheil–Gulliver model. This is due to the assumption that in the Scheil–Gulliver model, the solid stage has no diffusion, and the M23C6 was proved to precipitate in later stages of solidification as shown in the equilibrium phase diagram results. Finally, transmission electron microscopy (TEM) and x-ray diffraction (XRD) showcased the presence of the carbides predicted from the equilibrium phase diagram.

Stability of Ordered B2-β<sub>O</sub> and Disordered BCC-β Phases in Tial - A First Principles Study

Either at higher temperatures or when a certain alloying element content is exceeded, γ-TiAl alloys contain the β phase (bcc) or its ordered derivate βo (B2). The relatively soft β phase can facilitate hot deformation, but βo is detrimental for creep strength and ductility. Thus, knowledge about βo→β phase transformation is desirable. Surprisingly, even for the binary Ti-Al system it is under discussion whether the ordered βo phase exists. Also, the effect of alloying elements on the β phase ordering is still unclear. In the present work the ordering of the β phase in binary Ti-(39,42,45)Al and ternary Ti-42Al-2X alloys (X=Fe, Cr, Nb, Ta, Mo) which was experimentally investigated by neutron and high energy X-ray diffraction is compared with the results of first principles calculations using density functional theory. Except for Cr the experimentally determined and the predicted behavior correspond.

Эволюция микроструктуры и ее параметров с деформацией в поликристаллических сплавах медь - алюминий с разной энергией дефекта упаковки

Evolution of the dislocation structure during active plastic deformation was carried out in copper-aluminum alloys with Al content of 0.5-14 at. % using transmission electron microscopy. Analysis of the types of the dislocation substructure as a function of the alloying element content and deformation degree was conducted. The following parameters of the defect substructure were measured: average scalar dislocation density, curvature-torsion of the crystal lattice and microtwin density. The effect of stacking fault energy on accumulation of defects in the alloys was observed and evaluated.

Investigation of Selective Oxidation and Reaction Wetting of Q&P Steel Under Different Dew Point During Continuous Galvanizing

The effect of different dew points (−30 °C/− 10 °C) on the reactive wetting and selective oxidation of alloying elements of quenching and partitioning steel during continuous galvanizing was investigated. Morphology of the inhibition layer, the type of surface oxides and the variation of surface alloying elements concentration after galvanizing were all characterized. The results indicated that the enrichment of Si and Mn on the surface is lower after annealing at higher dew point, forming a more compact inhibition layer with a higher aluminum interior. Finally, better wettability of the steel during galvanizing and less leakage plating has been obtained. With the increase in dew point from −30 to −10 °C, the transformation of Si and Mn from outer oxidation to inner oxidation has occurred at 32 nm and 29 nm below the surface, respectively. Meanwhile, the oxidation depth becomes deeper.

Synthesis of Aluminum Alloys from Dispersed Waste Based on Aluminum

This paper presents the results of research on the synthesis of aluminum alloys of the Al–Si–Mg (Ak7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2), and Al–Mg–Mn (AMg5) systems using dispersed waste: beverage cans (Al–Mn–Mg system), sawdust of a cast alloy (Al–Si–Mg system), and twisted chips of deformable alloys of the Al–Cu–Mg and Al–Mg–Mn systems. A study of the microstructure of waste in the initial state is performed and the typical sizes of the main phases are determined. The main criteria for the quality of recyclable waste are determined: the purity (kp), contact with the atmosphere (ka), and maximum recovery of metal (ММе). Based on the proposed criteria, the waste is graded according to recycling efficiency. The lowest total score is assigned to cans of waste. Sawdust from the AK9ch alloy had the highest score. Experiments on the synthesis of Al–Si–Mg (Ak7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2), and Al–Mg–Mn (AMg5) alloys have shown that the usable yield varies from 82 to 96%. The minimum yield of usable material is set for the AK12 alloy, whose charge composition is dominated by beverage-can waste. The chemical compositions of the alloys in terms of the content of the main alloying and impurity elements meets the requirements of regulatory documentations. Tests of mechanical properties have shown that the synthesized alloys have a guaranteed margin of strength and plasticity in comparison with the requirements of regulatory documentation. Based on metallographic studies, it is found that the microstructure of synthesized alloys does not contain nonmetallic inclusions and gas porosity. Unmodified and modified samples from the Al–Mg–Mn alloy (AMg5) are subjected to cold rolling in several passes until cracks form. On the sample from an unmodified alloy, cracks appear after the tenth pass. The modified alloy sample withstands 12 passes before cracking. The degree of deformation in the thickness of the sample from the unmodified alloy is 60.5%; for the modified one it is 67.2%.

The Importance of Diffusivity and Partitioning Behavior of Solid Solution Strengthening Elements for the High Temperature Creep Strength of Ni-Base Superalloys

The creep resistance of single-crystalline Ni-base superalloys at elevated temperatures depends among others on solid solution strengthening of the γ-matrix. To study the influence of various solid solution strengtheners on the mechanical properties, a series of Ni-base superalloys with the same content of different alloying elements (Ir, Mo, Re, Rh, Ru, W) or element combinations (MoW, ReMo, ReW) was investigated. Nanoindentation measurements were performed to correlate the partitioning behavior of the solid solution strengtheners with the hardness of the individual phases. The lowest γ′/γ-hardness ratio was observed for the Re-containing alloy with the strongest partitioning of Re to the γ-matrix. As a result of the creep experiments in the high-temperature/low-stress regime (1373 K (1100 °C)/140 MPa), it can be concluded that solid solution hardening in the γ-phase plays an essential role. The stronger the partitioning to the γ-phase and the lower the interdiffusion coefficient of the alloying element, the better the creep resistance. Therefore, the best creep behavior is found for alloys containing high contents of slow-diffusing elements that partition preferably to the γ-phase, particularly Re followed by W and Mo.

Relationship between amounts of low-melting-point eutectics and hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification

Abstract A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point (LMP) eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification was performed. By controlling the concentrations of major alloying elements (Cu, Mg), the amounts of LMP eutectics at the final stages of solidification were varied and the corresponding hot tearing susceptibility (HTS) was determined. The results showed that the Al−4.6Cu−0.4Mg (wt.%) alloy, which contained the smallest fraction of LMP eutectics among the investigated alloys, was observed to be the most susceptible to hot tearing. With the amount of total residual liquid being approximately the same in the alloys, the hot tearing resistance is considered to be closely related to the amounts of LMP eutectics. Specifically, the higher the amount of LMP eutectics was, the lower the HTS of the alloy was. Further, the potential mechanism of low HTS for alloys with high amounts of LMP eutectics among ternary Al−Cu−Mg alloys was discussed in terms of feeding ability and permeability as well as total viscosity evolution during solidification.

Microstructural and Micromechanical Characteristics of Tin-Based Solders Under Self-Propagating Exothermic Reaction Heating

In this study, a rapid solder melting process has been examined through a self-propagating exothermic reaction using Al/Ni nanofoil as a localized heat source. Four kinds of tin-based solder preforms were partly melted under this process, and the thicknesses of the fusion zone in solder preforms around the Al/Ni nanofoil were experimentally analyzed. The microstructure and morphology of the fusion zone in different kinds of solder preforms were studied by metallographic analysis. In Sn42Bi58 solder, the mean grain size of Bi-rich phases in the fusion zone was finer than the original structure, and decreased from ~ 2.7 μm to ~ 0.8 μm away from the Al/Ni nanofoil. Similar trends of mean size of grains in the fusion zone were also found in the Sn, Sn-3 wt.%Ag-0.5 wt.%Cu(SAC), and SnPb solder preforms. The widths of the fusion zone in the Sn, SAC, SnPb, and SnBi solder preforms were 150 μm, 173 μm, 188 μm, and 233 μm, respectively. In addition, the nano-hardness and distribution in the fusion zones were evaluated. The results show that the value of nanohardness increased along with the decrease of distance from Al/Ni nanofoil. The average hardness and the lower and upper bounds of Sn, SnPb, SAC, and SnBi solder in the fusion zone are 0.260 (−0.045, +0.039) GPa, 0.246 (−0.059, +0.114) GPa, 0.260 (−0.014, +0.070) GPa, and 0.404 (−0.072, +0.134) GPa, respectively. The statistical significance of solder hardness is related to its alloy component, element content, and microstructure.

Study on solid-solution interaction and existing forms of alloying elements in Mg–Al–Zn-Gd alloy

Mg–9Al-0.7Zn-0.9Gd(wt%) alloy was prepared by die casting. The solid solution amount of alloy elements was determined. The solid solution ability of alloy elements was analyzed by using the first principle. The activity interaction coefficient was calculated by using the relevant thermodynamic model to explore the effect of solid solution between elements. Determine and calculate the content of alloy elements in each phase, and analyze the specific role of alloy elements in the alloy. The results show that Al has the largest amount of solid solution in the alloy, while Zn and Gd have relatively small amounts of solid solution. The reason for the small amount of Gd solid solution is that chemical reaction between Gd and Al took place before α-Mg was formed, consuming most of Gd. The solid-soluble Al has repulsive effect on Zn, which leads to the decrease of the solid-soluble ability of Zn. Therefore, the solid-soluble amount of Zn in α-Mg is very small, and most of Zn is solid-soluble in Mg17Al12. Al plays the role of solid solution strengthening and second phase strengthening in the alloy, while Zn plays the role of grain refinement and solid solution strengthening of Mg17Al12 in the alloy. Gd mainly exists in the form of Al2Gd, which plays a role in strengthening the second phase, but Al2Gd can be used as heterogeneous nucleation particles to play a role in grain refinement.

Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering.

The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m−3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m−3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10−7 A/cm2 to 6.78 × 10−7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work.

Application of generalized regression neural network optimized by fruit fly optimization algorithm for fracture toughness in a pearlitic steel

In this paper, a generalized regression neural network(GRNN) optimized by fruit fly optimization algorithm (FOA) was developed to improve the predictive accuracy of small number of samples. Then the quantitative relationship between alloying elements and fracture toughness was further investigated based on the developed model. The steels were produced by arc melting and heat treatment. The toughness was measured by a three-point bending method used for FOA-GRNN output. The characteristic factors used for input variables were alloying element content. The performance evaluation indices calculated for the improved models were compared with the results obtained by the GRNN model. As a result, the FOA-GRNN model was found to be successful for predicting toughness with high accuracy and good generalization ability for the studied steels. Through the sensitivity analysis, the results indicate that the sequence of influencing factors is Nb > C > Mn > S > Si > P > Cr > V. Then the interact effect of alloying elements on the fracture toughness were studied, and the composition parameters of the steel were optimized by the developed model.

Compressive behavior and elastic properties of Ni-based γ/γ’ ternary model superalloys: First-principles calculations and rule of mixtures predications

Using a total-energy method based on the density functional theory (DFT), the strengthening effects of Mo, Ta, W, and Re on the ideal uniaxial compressive strength (σICS) and elastic properties of Ni-based single-crystal (NBSC) superalloys were systematically investigated using a model consisting of γ/γ′ multilayers. The ability of the ternary alloying elements to enhance σICS, the elastic constants, and elastic modulus were in the order: Re > W > Mo > Ta. Our calculated elastic properties were consistent with reported experimental results for commercial superalloys (e.g., CMSX-4 and TMS-26), as well as with other reported computational results. Furthermore, the charge density difference of the γ/γ′ ternary alloys during compressive deformation were analyzed to understand the strengthening mechanisms of the alloying elements. The mechanical properties of the γ/γ′ ternary model alloys were predicted by modifying the first-order rule of mixtures (ROM) with the alloying element concentrations, and the determined values were in close agreement with the results of the first-principles calculations.

SEM Studies on the Microstructure and Phase Composition Distribution in Cr<sub>3</sub>C<sub>2</sub> + TiC Claddings on Low-Carbon Steel

Using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) we studied the distribution of structural parameters, phase composition and alloying elements concentration across the coatings obtained by cladding of chromium and titanium carbides mixture on low-carbon steel. The beam of relativistic energy electrons extracted into the atmosphere was used to form the coatings. The homogeneity in the allying elements distribution is shown to be defined by the lifetime of the melt bath while the phase composition distribution depends on the thickness of the melt layer. Both above parameters are determined by the density of the entered energy.

Microstructure, mechanical properties and hydrogen permeability of multiphase V-Ti-Ni alloy membranes

Multi-phase V-Ti-Ni alloys membranes consist of primary V-based solid solution (Vss) for hydrogen permeation and eutectic phases with high hydrogen embrittlement resistance. Different element content in the alloy results in the different microstructures, and their effects on mechanical properties and hydrogen permeability have been studied for the V-Ti-Ni alloys (V70Ti15Ni15 and V60Ti20Ni20) with equal Ni/Ti atom ratio. The increase of Ti and Ni content in the alloys leads to the rise of interdendritic phase (Ni-Ti compounds) volume fraction. The mechanical property testing shows the strength, hardness and plasticity of the alloys both increase with the increase of Ti and Ni, which refer to a larger combination effect of solid solution hardening and particle strengthening, and the volume fraction of NiTi phase in the alloy. Hydrogen permeability of V60Ti20Ni20 alloy membrane is 4.2 × 10−8 mol m-1s-1 Pa-0.5, which is more than twice that of Pd-25Ag alloy membrane at 673 K, and has better hydrogen embrittlement (HE) resistance. Increasing the proportion of NiTi phase is beneficial to improving the mechanical properties and HE resistance of the alloy membrane. The alloy membranes for hydrogen permeation with good comprehensive performance can be obtained by properly adjusting alloying element content and controlling phase composition.

Effects of Ni and Cu Addition on Tensile Properties and Thermal Conductivity of High Pressure Die-cast Al-6Si Alloys

In this study, the effects of nickel and copper on the mechanical and thermal properties of Al-Si alloys were investigated, for different alloy compositions. Thermodynamic calculations were carried out to predict the alloys’ solidification behavior (solidification temperature, solid fraction and physical properties (density, thermal conductivity, elastic modulus, bulk modulus)). The aluminum alloys were produced by high pressure die-casting process with a 125 ton die-casting machine. Microstructures in the Al-Si-Ni alloys were characterized by optical microscopy and scanning electron microscopy. The mechanical properties were evaluated by tensile tests. Thermal conductivity was measured using a laser flash method. The addition of Ni and Cu improved the mechanical properties of the alloys by different strengthening mechanisms. Solution strengthening was the more effective method of improving mechanical properties, compared with strengthening by intermetallic compounds. The addition of an appropriate concentration of soluble alloying elements consistently improved alloy strength. However, addition of alloying elements decreased the thermal conductivity of the primary alpha aluminum phase. EDS analysis confirmed that soluble alloying elements like Cu not only can form intermetallic compounds, but can also change other kinds of compounds. Accordingly, careful consideration should be given to the chemical composition of soluble/insoluble alloying elements when attempting to improve mechanical properties and thermal conductivity at the same time.

Improving Service Durability for Tooling Made of Heat Resistant Austenitic Steel by Barium-Strontium Carbonatite Treatment

The use of heat-resistant steels with a required chemical composition and increase in the alloying element content in the manufacturing of equipment for thermally loaded units do not guarantee any required durability and resources thereof. The causes of the decrease in the tool’s heat resistance are revealed, and a method for increasing this parameter is proposed using the steel melt treatment by alkaline-earth carbonatites, which promotes the following: provides its homogenization, improves casting properties and reduces the level of casting defects.

Development and Modeling of Differentially Heat-Strengthened Rail Welding: Welding and Local Heat Treatment Modeling

During the manufacturing of continuous welded rail track, the problem of the local hardened points in the welded joint during rail joint welding is resolved by using local heat treatment of the welded joint. As a result, the quenching structure formation is excluded. However, the appearance of new heat-affected zones with reduced hardness is possible. During operation, such rails are characterized by increased tread surface wear in these areas and rail flattening at the welded joint, which is the main reason for retiring the rails from service earlier than the guaranteed service life. A new technology based on the dependence of the structural component dispersion (primarily perlite and carbide particles formed in the process of rail butt welding) is proposed for the steel composition and cooling conditions. The cooling rate has a decisive influence on the dispersion degree of the ferrite-cementite structure formed during the austenite decomposition. During the welding rail process, the granular perlite formation is possible in a butt weld in areas with a temperature ranging within points Ac1 and Acm. To determine these critical temperatures, thermodynamic calculations were performed using the Thermo–Calc® software (TCFE database) allowing the chemical composition of the samples obtained by spectrometry. The iron–carbon state diagrams for rail steel 76KhSF with the minimum and maximum alloying element content according to GOST R 51685–2013 are modeled. To obtain the minimum number of sections with reduced hardness, it is possible to weld rails using shot discontinuous flash welding. In order to eliminate the formation of defective areas with a quenching structure, it is possible to control the cooling of the welded joint by contact heating. Temperature distribution measurement during welding according to given modes and controlled cooling confirms the theoretical conclusions.

Development and characterization of β‐type Ti‐Zr‐Nb‐Sn dental implant materials

AbstractTo develop new materials of proper elastic modulus and biocompatibility for dental implants, Ti‐2Zr‐xNb‐xSn (x = 0, 0.1, 0.2, 0.3) and Ti‐2Zr‐xNb‐xMo (x = 0, 0.1, 0.2, 0.3) alloys were designed and fabricated. Effects of alloying elements on properties and the feasibility of application in dentistry are analyzed. It is indicated that Nb, Sn and Mo obviously influence the phase compositions of Ti‐2Zr‐based biological alloys. With the increase of alloying element content, all the alloys tend to form a single β‐Ti phase. Ti‐2Zr‐xNb‐xSn alloys exhibit better mechanical properties and corrosion resistance than the Ti‐2Zr‐xNb‐xMo alloys. The Ti‐2Zr‐0.1Nb‐0.1Sn alloy has proper elastic modulus (14.72 GPa) (which is very close to the natural bones), excellent corrosion resistance and comprehensive mechanical properties, and is considered as ideal candidate for implant materials.