Effect Of Alloying Elements Research Articles

First-principles study of transformation strains and phase stabilities in α″ and β Ti-Nb-X alloys

Effects of third alloying elements on the transformation strains and phase stabilities of Ti-Nb based alloys at 0 K were investigated using the first-principles calculations. In binary Ti-Nb alloys, the transformation strains and the body-centered cubic high-temperature beta (β) phase stabilities decrease with increasing Nb concentration. In Ti-12.5Nb-6.25X (at.%) alloys, the effects of 46 different alloying elements X on the transformation strains and phase stabilities were also investigated. The addition of Al, Be, Ca, Cu, Ga, Ge, Hf, La, Mg, Sc, Si, Sn, Sr, Y, Zn, and Zr increase the transformation strains, and all alloying elements except for Sc act as the β-phase stabilizing element. Using the calculated values of the effects of alloying elements, xM values were calculated for the different 46 alloying elements, where xM are the X contents of Ti-12.5Nb-X (at.%) ternary alloys where the martensitic transformation start temperatures were equal to 300 K. Then, the transformation strains of Ti-12.5Nb-xMX (at.%) alloys were predicted. The Ti-12.5Nb-17.8Hf (at.%) alloy shows the largest transformation strain value.

Research and Development of Cold Rolled Hot-dip Galvanized DP590 Steel with Low Cost

Two low-cost cold rolled hot-dip galvanizing DP590 steels with different alloy elements were designed and the effects of alloy elements and galvanizing process parameters on the microstructure and mechanical properties were investigated. The results show that both of the experimental steels exhibit typical dual phase microstructure. Compared to the steel with higher silicon, the ferrite phase of steel with higher chromium is more pure and martensite-austenite (MA) islands are more evenly distributed. Both of the steels satisfy the mechanical properties standard of cold rolled hot-dip galvanizing DP590 steel, while steel with higher chromium has better elongation.

The effect of alloying elements on the ductility of Al-Mg-Si alloys

Experiments were conducted to document the combined effect of different alloying elements on the microstructure and associated stress-strain behavior of extruded Al-Mg-Si alloys, with a special emphasis on the ductility to fracture characteristics. Four alloys with different concentrations and relative amounts of Mg, Si, Fe, Cu, and Mn were selected for examination. In order to obtain an accurate description of the strength-ductility relationship, tensile testing was performed with a laser extensometer, and scanning (SEM) and transmission microscope (TEM) studies were carried out to correlate the microstructure and fracture characteristics with the stress-strain behavior. Excess-Si (Mg/Si<1.73) was found to have a detrimental effect on the ductility of Al-Mg-Si alloys without the presence of additional alloying elements, leading to fracture occurring partly intergranularly. This was linked to the segregation of free Si at grain boundaries, forming coarse Si-particles, and the formation of Mg2Si particles during solution heat treatment. Adding Fe and Cu improved the ductility and strength, which could be attributed to a lower solvus temperature and increased formation of primary particles, resulting in less free Si for embrittlement of grain boundaries. The highest ductility was found by introducing Mn, which in addition to tie up free Si to second-phase particles, suppressed recrystallization by forming dispersoids. The most desirable combination of tensile strength and ductility was found in an excess-Mg alloy (Mg/Si>1.73) with additions of both Mn and Cu.

Cr-Mo鋼の溶接金属の再熱割れ感受性に及ぼすCおよびBの影響

Reheat cracking during post weld heat treatment (PWHT) generally occurs in the coarse grain HAZ (heat affected zone) of Cr-Mo steel and 780MPa class high strength steel. Although reheat cracking in the weld metal of Cr-Mo steel has also become well-known recently, the effect of alloy elements in the weld metal on reheat cracking had not been investigated in detail. In particular, the small amounts of alloy elements such as carbon and boron in the weld metal are affected partly by dilution components from the base metal. The purpose of this study was to clarify the effect of the carbon and boron contents on reheat cracking susceptibility in the weld metal of Cr-Mo steel. Reheat cracking tests were carried out by the C-ring and constant stress methods. Reheat cracking susceptibility and the hardness of weld metal containing up to 0.08mass% carbon clearly increased with increasing boron contents over 3ppm. However, reheat cracking of weld metal containing approximately 7ppm boron was suppressed by increasing the carbon content in spite of an increase in hardness. The constant stress reheat cracking tests showed experimentally that the high temperature strength of the grain boundary in weld metal containing boron decreased with increasing temperature during PWHT. Secondary Ion Mass Spectrometry (SIMS) and precipitate analysis revealed that the existence form of boron on the grain boundary changed from dissolved to precipitated during PWHT, and thermo-dynamic calculation showed an increase of M23C6 carbide with increasing carbon contents. Based on these results, it was estimated that the reheat cracking susceptibility of weld metal increased by intergranular embrittlement due to precipitation of boron nitride and decreased by grain boundary strengthening due to the increase of M23C6 carbide.

Research of Deformation Law on High Manganese Steel with Different Alloy Composition

The organizations and phase composition after forging and heat treatment of the stacking fault energy for the three high manganese steel with 2.99 mJ/m2,7.9 mJ/m2and23 mJ/m2 were observed. It’s analysised that the microstructure and orientation change of three high manganese steel by SEM and EBSD and the effect of alloy elements and the composition of the material on microstructure of high manganese steel; Through Static compressive deformation of cylindrical specimen under different strain rates experimental, the effect of strain rate on the deformation mechanism of different components of high manganese steel was analysised. Cylindrical specimens by static compression at different strain rates, analysis of strain rate on the different components of high manganese steel impact deformation mechanism; The mechanical performance characteristics are analyzed under different strain rate of three components high-manganese steel by stress - strain curves. By Compressive Split-Hopkinson Pressure Bar experiments to study the mechanism of high manganese steel deformation at high strain rates. The study found: the exclusion of the impact of the martensitic transformation can produce 18Mn high manganese TRIP or TWIP effect after deformation. Through observation and calculation, it found C, Al's content of alloying elements on the grain sizes less affected, but the starting temperature of martensitic transformation and layer greatly affects high manganese wrong size possible. Through analysis, found C, Al decides that the high content of alloying elements manganese organization original phase composition and deformation mechanism; organizations γ + ε-M + α'-M high manganese TRIP effect occurs, organizations γ + ε-M's high manganese TRIP effect occurs, tissue TWIP effect of high manganese steel γ.

Research on adiabatic shear failure character of pure copper and aluminum bronze based on empirical electron theory

The valence electron structure (VES) parameters affecting adiabatic shearing failure under high speed impact load using split Hopkinson pressure bar (SHPB) were studied by empirical electron theory (EET) of solids and molecules. There is a problem of multiple solutions about VES parameters in EET. The statistics values of VES parameters related to adiabatic shearing sensitivity were calculated to substitute for the most probable value among the multiple solutions according to the view that the microstate statistics values can reflect the macro physical quantity. The research shows that the adiabatic shearing sensitivity is growing with the rise of the statistics value of bond energy of the strongest covalent bond, and is decreasing with the rise of the statistics value of the lattice electron number. The statistics value of bond energy of the strongest covalent bond in aluminum bronze (QAl9-4) is larger than that in pure copper, and the statistics value of the lattice electron number in QAl9-4 is smaller than that in pure copper. Therefore, QAl9-4 is prone to adiabatic shearing failure, and the grains were only elongated due to the large deformation for pure copper without any adiabatic shear band (ASB). It is of great significance for the selection and design of material with different adiabatic shearing sensitivity to research the effect of alloy elements on adiabatic shearing sensitivity from the electronic structure perspective.

The effect of alloy elements on the density variation of steel melt at the interdendritic region during solidification

Alloying elements in steels have essential effects on the formation of macrosegregation by inducing a density difference between the mushy zone and the bulk melt, and even by the alteration of the solidified microstructure. Hence, in terms of the thermodynamic laws for solidification of an idealized dilute solution, a systematic theoretical analysis on the effect of elements on the density variation of the interdendritic melt is presented for common Fe-based binary alloys. It shows that density variation closely associates with three crucial parameters: the microsegregation parameter λ, the temp-comp-expansion parameter β and the initial composition CLo. With these derived parameters, a simple analytical model is proposed to assess the influence of alloy elements on density change. The theoretical analysis indicates that compared to silicon, the effect of carbon on the density variation cannot be ignored, which is remarkably different from the previous recognition of these two elements. The macrosegregation induced by carbon only is experimentally validated by two dissected 500 kg ingots with different carbon contents. Furthermore, to directly validate the results of theoretical analysis a macrosegregation model with two different microsegregation laws (lever rule and Scheil equation) is established. Then simulations of the convection during solidification in the experimental 500 kg reference ingot are performed for Fe-C and Fe-Si alloys, respectively. It demonstrates that numerically simulated effects of carbon and silicon on the interdendritic convection induced by density inversion are fairly consistent with the analytical predictions.

Research on Effect of Alloy Elements on Equilibrium and Properties of Ni-Cr-Co Type Nickel-Based Superalloy

Ni-Cr-Co type Nickel-based super alloy Inconel 740H was studied. The effect of Nb, Al and Ti on the equilibrium of this alloy was analyzed by JMatPro software. The amount of Ti and Nb should be controlled by 1.50wt.%, and meanwhile, Al should be 1.0-2.0wt.%. If Mo and W were added the amount of Mo should be in the range of 1.0-2.0wt. %, and W should be about 1.0wt.%. Based on these results, three types of new alloys were designed, which contain Ni-Cr-Co-Mo type (1#), Ni-Cr-Co-W type (2#) and Ni-Cr-Co-Mo-W type (3#). Compared with the Ni-Cr-Co type Inconel 740H alloy, the room temperature strength, high temperature strength and high temperature durable performance of the three new alloys improved, which can provide the evidence and reference to optimize the chemical composition of Inconel 740H alloy, i.e., adding 1.50wt.% Mo and 1.0wt.% W individually or together.

The Effect of Interfacial Element Partitioning on Ferrite and Bainite Formation

The formation of bainitic ferrite and that of grain boundary ferrite in low alloy steels have been two of the most important and interesting research topics in the field of solid state ferrous phase transformation for several decades, and various aspects of these two transformations have been discussed extensively in the literature. Recently, a so-called Gibbs energy balance (GEB) model was proposed by the authors to evaluate alloying element effects on the growth of bainitic ferrite and grain boundary ferrite. The model predicts a growth mode transition from paraequilibrium, negligible partitioning to partitioning during the isothermal formation of bainitic ferrite and grain boundary ferrite. Transformation stasis and bay phenomenon are well explained by the GEB model and both of them are found to be due to alloying element diffusion at the interface. This overview gives a summary of the authors’ recent progress in the understanding of the growth of bainitic ferrite and grain boundary ferrite, with particular focus on the growth mode transition, the transformation stasis phenomenon and the bay phenomenon.

Prediction of Phase Composition and Nitrogen Concentration During the Nitriding Process in Low-Alloy Steel

A diffusion/transformation coupled model has been developed which combines finite difference (FD) model with a phenomenological model. The composition of the different iron-nitrogen(Fe-N) hardening phase can be regard as a function of nitriding time and nitrogen concentration. The diffusion model and transformation model are linked by the limiting nitrogen solubilities and the effective diffusion coefficients. The effect of alloy elements (Cr, Mo, Mn, V, Ni etc.) is considered by introducing an alloy coefficient for limiting nitrogen solubilities and diffusion coefficient. The diffusion/transformation model can predict nitrogen concentration, phase composition and hardness distribution. The model is employed to simulate the nitriding process of SCr420H low-alloy steels. The simulated nitrogen concentration and hardness profiles are consistent with the measured ones. In addition, the predicted depth distributions of iron-nitrogen phase agree well with the available experimental results. Therefore, the comparison shows the reliability of the coupled model. It can be applied to improve the nitriding process parameters.

Elastic-modulus enhancement during room-temperature aging and its suppression in metastable Ti–Nb-Based alloys with low body-centered cubic phase stability

Changes in the elastic properties during room-temperature aging (RT aging) of metastable Ti–Nb-based alloy single crystals with low body-centered cubic (bcc)-phase stability were investigated. The elastic stiffness components of Ti–Nb–Ta–Zr alloys with different Nb concentrations were measured by resonant ultrasound spectroscopy during RT aging; the results revealed that shear moduli c′ and c44 were increased by RT aging. In the alloy with the lowest Nb concentration, i.e., with the lowest bcc phase stability, shear moduli c′ and c44 were enhanced by the largest amount. The increase rates were ∼5% for 1.1 × 107 s (127 days), whereas the bulk modulus was hardly changed by aging. In Ti–Nb–Ta–Zr–O alloys with different oxygen concentrations, shear moduli c′ and c44 of the alloy with the lowest oxygen concentration increased most significantly. Moreover, the electrical resistivity of Ti–Nb–Ta–Zr and Ti–Nb–Ta–Zr–O alloys was increased by RT aging. Importantly, the enhancements of shear moduli and electrical resistivity were suppressed by increases in the bcc-phase stability (i.e., increase in the Nb concentration) and oxygen concentration; these factors are known to suppress ω (hexagonal) phase formation. However, transmission electron microscopy (TEM) observations revealed that only a diffuse ω structure—an ω-like lattice distortion—was formed after RT aging. On the basis of alloying element effects, TEM observations, and analysis of the changes in elastic properties by using a micromechanics model, it was deduced that the enhancements of shear moduli and electrical resistivity were possibly caused by the formation of a diffuse ω structure.

Effect of Alloy Elements on the Corrosion Resistance and Electrical Conductivity of Austenitic Stainless Steel for MCFC

Bipolar plate and current collector are important stainless steel components of MCFC because they supply the pathway of the electron flow between each unit cell. However these stainless steel components are prone to corrosion in the hot corrosion environment and corrosion products forming on the surface increase the ohmic resistance. To solve these problems, alloy elements are added to modify the properties of the oxide layer on the surface. High Cr content causes the formation of thin oxide layer, therefore, improves the corrosion resistance. Mn enrichment occurs in the oxide layer and may lead to an increase in electrical conductivity.

Analysis of the effect of alloy elements on allotropic transformation in titanium alloys with the use of cohesive energy

A simple model to account for the effect of alloy elements on allotropic transformation in titanium alloys is described using the cohesive energies calculated with the self-consistent bond length difference (SCBLD) method in the empirical electron theory (EET) of solids and molecules. The results indicate the total cohesive energy (SE‾c) as well as cohesive energy difference (ΔE‾c) for α and β phases can be used to investigate the influence of alloying elements on the allotropic transformation of β to α. Moreover, the deterministic model agrees well with the experimental results.

Effect of Alloy Elements on Microstructure of Modified Area via Friction Stir Process in Steel Materials

Effect of Alloy Elements on Microstructure of Modified Area via Friction Stir Process in Steel Materials

Effect of Alloy Elements on the Corrosion Resistance and Electrical Conductivity of Austenitic Stainless Steel for MCFC

Bipolar plate and current collector are important stainless steel components of the molten carbonate fuel cell (MCFC) because they supply the pathway of the electron flow between each unit cell. However, these stainless steel components are prone to corrosion in the hot corrosion environment and corrosion products forming on the surface increase the ohmic resistance. In addition, hot corrosion reduces the mechanical strength of the current collector, accelerates electrolyte loss, and finally leads to degradation in cell performance. Therefore, corrosion of stainless steel components is one of the main problems in MCFC systems. To solve these problems, various methods have been studied, such as addition of alloy elements, surface coatings and replacement with higher grade materials. Corrosion resistance of stainless steels is evaluated by potentiodynamic polarization test and weight loss measurements. Electrical conductivity of specimens is measured in molten carbonate at 650 oC. Results from electrochemical tests show that high Cr content causes the formation of a dense and thin oxide layer, subsequently improving the corrosion resistance. However, high Cr content gives rise to inner oxide penetration. Mn enrichment occurs in the oxide layer and may lead to an increase in electrical conductivity. In addition, minor elements such as Si, Nb and N may contribute to the improvement of corrosion resistance and electrical conductivity.

Effect of alloy elements on the morphology transformation of TiB2 particles in Al matrix

To reveal the effect of alloy element on the morphology of in situ TiB2 particles, a series of TiB2 particles with various morphology were obtained via controlling synthesis process. Si and Cu can affect the morphology transformation of TiB2 particles significantly. Si preferentially adsorbed on (1 0 1¯ 1), (1 1 2¯ 0) and (1 2¯ 1 3¯) planes resulting in the polyhedron morphology of TiB2. Cu adsorbed on (1 0 1¯ 0) preferentially leading to the minimum aspect (the ratio of the diameter and thickness).

Effects of Alloy Elements on Oxidation Resistance and Stress-Rupture Property of P92 Steel

Effects of alloy elements Cr, W, Ce, and Si on oxidation behavior at 750 °C in air and stress-rupture properties of P92 steel have been investigated. The proper increase in elements Cr, W, and Ce improved to varying degrees both oxidation resistance by either facilitating more protective Cr2O3 or modifying surface morphologies and stress-rupture life largely attributed to the formation of fine Laves phase. The excessive addition of Si significantly improved oxidation resistance of P92 steel, but dramatically impaired the stress-rupture life due to the formation and coarsening of Laves phase. The results indicate that proper additions of Cr, W, and Ce are beneficial for the comprehensive property of P92 steel.

해수환경하에서 스테인리스강의 전기화학적 특성 개선을 위한 합금원소의 영향

해수환경하에서 스테인리스강의 전기화학적 특성 개선을 위한 합금원소의 영향

Effect of alloy element on corrosion behavior of the huge crude oil storage tank steel in seawater

Corrosion behaviors of the high strength low alloy (HSLA) steel and the carbon steel for a huge crude oil storage tank in seawater were studied by electrochemical methods and microanalysis techniques. The research found the alloy element had decreased corrosion rates for a long time but slightly increased corrosion rate at the beginning of experiments. Potentiodynamic tests results showed that all specimens exhibited active corrosion behavior, and corrosion rate tended to increase as a result of adding alloying elements. However, the loss weight results showed the corrosion rates of the HSLA steel were much smaller than those of carbon steel. Furthermore, more alloying elements led to a remarkable decrease in the corrosion rate. The reasons for these by electrochemical impedance spectroscopy (EIS) showed that the corrosion process of all samples showed two stages. At the first 144h, EIS of all samples showed one increasing capacitance arc. The carbon steel showed the least corrosion rate, which was due to that the corrosion rates depended on the active site on the sample surface and the alloy effects were minor. After 144h of immersion, EIS of the HSLA steels showed two capacitance arcs and the EIS of the carbon steel always showed one capacitance arc, which indicated the HSLA steel can form a compact corrosion scale. The HSLA steel showed the smaller corrosion rate than carbon steel, which was due to that the corrosion rates depended on the protective ability of corrosion scales and the alloy elements were help to form a compact corrosion scale on sample surface. The EDS results indicated that Cr, Mo and Al were distributed densely at the interface between the rust layer and the steel surface which helped to improve corrosion resistance for the HSLA steel. Corrosion of the HSLA steels was suppressed by insoluble compound formed near the surface.

Progress in the understanding of Ni silicide formation for advancedMOSstructures

Metallic silicides have been used as contact materials on source/drain and gate in metal‐oxide semiconductor (MOS) structure for 40 years. Since the 65 nm technology node, NiSi is the preferred material for contact in microelectronic due to low resistivity, low thermal budget, and low Si consumption. Ni(Pt)Si with 10 at.% Pt is currently employed in recent technologies since Pt allows to stabilize NiSi at high temperature. The presence of Pt and the very low thickness (&lt;10 nm) needed for the device contacts bring new concerns for actual devices. In this work,in situtechniques [X‐ray diffraction (XRD), X‐ray reflectivity (XRR), sheet resistance, differential scanning calorimetry (DSC)] were combined with atom probe tomography (APT) to study the formation mechanisms as well as the redistribution of dopants and alloy elements (Pt, Pd…) during the silicide formation. Phenomena like nucleation, lateral growth, interfacial reaction, diffusion, precipitation, and transient phase formation are investigated. The effect of alloy elements (Pt, Pd…) and dopants (As, B…) as well as stress and defects induced by the confinement in devices on the silicide formation mechanism and alloying element redistribution is examined. In particular APT has been performed for the three‐dimensional (3D) analysis of MOSFET at the atomic scale. The advances in the understanding of the mechanisms of formation and redistribution are discussed.