Effect Of Different Alloying Elements Research Articles

Investigation of the surface of antifriction Al–Cu–Si–Sn–Pb aluminum alloys

The tribological and mechanical properties of Al–Cu–Si–Sn–Pb alloys are studied. The effect of different alloying elements on the structure of their surface and its tribological properties is estimated. The alloys are studied at different stages of their production, i.e., after casting and homogenizing annealing. The character of surface transformations under friction simulated on fiction machines is investigated. The surface is visualized by means of optical and scanning probe microscopy and scanning electron microscopy combined with elemental analysis. Great amounts of oxygen leading to the formation of oxide particles with abrasive properties are revealed on the contact surfaces. The mass transfer of chemical elements also occurs in the contact area: the material of an insert “spreads” over the shaft to form a film of secondary structures. At small thicknesses, this film serves as a solid lubricant, but might promote the formation of scoring during the development of microrelief. The application of two hardness measurement methods, such as “microindentation” and “nanoindentation”, give mutually complementary results. The highest mechanical properties (hardness, up to 0.5 GPa) are established to be attained in silicon- and copper-containing alloys. Homogenizing annealing at 400°C is also revealed to decrease the hardness, but improve the plasticity, which is important for antifriction materials.

High-temperature oxidation behavior of Nb–Si-based alloy with separate vanadium, tantalum, tungsten and zirconium addition

The microstructure and oxidation behavior of directionally solidified (DS) Nb–15Si–24Ti–4Cr–2Al–2Hf alloys with separate vanadium, tantalum, tungsten and zirconium additions were investigated by X-ray diffraction (XRD), electron probe microanalyzer (EPMA) equipped with wave-dispersive spectroscopy (WDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy-dispersive spectroscopy (EDS). Results show that the five alloys are all composed of primary (Nb,Ti) solid solution ((Nb,Ti)SS) phase and eutectic (Nb,Ti)SS/(Nb,Ti)5Si3 structure. After oxidation at 1250 °C for 100 h in air, the surfaces of the five alloys are covered by the oxides of Nb2O5, TiNb2O7, Ti2Nb10O29, TiO2 and amorphous SiO2. It is found that the alloying elements of V and W are detrimental for oxidation resistance and the addition of Ta has no obvious effect. Zr addition obviously benefits the oxidation resistance at high temperature, by decreasing the weight gain from 242.75 to 184.83 mg·cm−2. The oxidation mechanism of Nb–Si-based alloys and the effects of different alloying elements on the oxidation resistance of Nb–Si-based alloys were discussed.

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.

Formulation of the Effect of Different Alloying Elements on the Tensile Strength of the in situ Al-Mg2Si Composites

In this paper, the effect of different alloying elements on the ultimate tensile strength of Al-Mg2Si composites is theoretically studied. The feed forward back propagation neural network with sigmoid function is used. The extensive experimental results taken from literature are modeled and mathematical formula is presented in explicit form. In addition, it is observed that magnesium and copper have a stronger effect on the ultimate tensile strength of Al-Mg2Si composites comparison to other alloying elements. The proposed model shows good agreement with test results and can be used to find the ultimate tensile strength of Al-Mg2Si composites.

Composition Optimization and Experimental Characterization of a Novel Steel Based on CALPHAD

A new steel with high Cr and low W, Mo contents for forged cold work roll was designed based on the composition system of traditional high-speed steel roll. The Fe-C isopleths of the steel and the mass fraction of equilibrium phases versus temperature were calculated by Thermo-Calc, and the effects of different alloying elements (W, Mo, Cr, V) on austenite, ferrite, and carbides (MC, M6C, M7C3, M23C6) were also established to optimize the composition and structure. The designed and optimized specimens were both quenched at 1100 °C and then tempered twice at 560 °C. The hardness and wear resistance of the samples were measured. The microstructures of quenched tempered and forged specimens were studied. The results show that ferrite crystallization, peritectic reaction, austenite crystallization, and the precipitation of MC, M6C, M7C3, M23C6 occur during equilibrium solidification process. The alloying elements W, Mo mainly affect the precipitation of M6C, while Cr affects the precipitated region and mass fraction of M7C3. Higher V content widens the high-temperature region of the peritectic reaction and results in a large amount of MC precipitation. The optimized composition (wt.%) for cold work roll steel is 1.30-1.35%C, 9-10%Cr, 2.5-3.0%Mo, 0.5-1.0%W, 2.5-3.0%V, 0.5-0.6%Mn, 0.5-0.6%Si. The hardness of the steel after quenching and tempering is 60.8 HRC and weight loss after 120 min is 6.2 mg. This meets the requirement of hardness and wear resistance requirements for cold work roll. The ledeburite in the optimized steel disappears after forging and the carbide network break into a large amount of tiny blocky ones dispersed in the matrix without cracks, which shows a good forgeability of the steel and rationality of the optimized composition.

Electrochemical and Salt Spray Corrosion Behavior of Copper Alloy Contact Wires in Chloride Solution

The effect of different alloying elements on corrosion behavior of copper alloys was investigated using electrochemical corrosion and salt spray corrosion test in NaCl solution. Cu-Ag has the most stable corrosion current in the potentiostatic scanning test, exhibiting a better corrosion resistant performance. It can be analyzed from corrosion surface morphologies that Cu-Ag presents exfoliation corrosion mechanism while Cu-Sn shows crevice corrosion mechanism. Cu-Mg has a complex corrosion process caused by multiple corrosion mechanism. In the salt spray corrosion test, the corrosion degree of Cu-Ag is lighter than those of Cu-Sn and Cu-Mg after 24h test. Therefore, the Cu-Ag alloy exhibits the best corrosion resistance in chloride solution.

In Situ Quantification of Micro‐Segregation that Occurs During the Solidification of Steel

We present a method for the in situ quantification of micro‐segregation during the solidification of steel by using high‐temperature laser‐scanning confocal microscopy (HTLSCM). A newly developed experimental technique that has been developed for HTLSCM has been utilized to investigate the effect of different alloying elements and cooling rates on the solidification behavior of steel. An automated quantitative measurement of the fractions of solid and liquid during solidification is used to calculate the average phase concentrations by applying a simple mass balance. The results of these analyses are in very good agreement with simulations carried out by using the commercial software package DICTRA.

Prediction of porosity percent in Al–Si casting alloys using ANN

In this investigation a theoretical model based on artificial neural network (ANN) has been developed to predict porosity percent and correlate the chemical composition and cooling rate to the amount of porosity in Al–Si casting alloys. In addition, the sensivity analysis was performed to investigate the importance of the effects of different alloying elements, composition, grain refiner, modifier and cooling rate on porosity formation behavior of Al–Si casting alloys. By comparing the predicted values with the experimental data, it is demonstrated that the well-trained feed forward back propagation ANN model with eight nodes in hidden layer is a powerful tool for prediction of porosity percent in Al–Si casting alloys.

Effects of different alloying elements on the hardness profile of nitrided hot-work tool steels

Hot-work tool steels contain several strong nitride forming elements such as Cr, V and Si which is taken advantage of widely in the nitriding of steels for many applications. This paper presents the effects of different alloy compositions of hot-work tool steels, including standard grades, new vacuum remelted high-performance grades and some model alloys, on the hardness profile after nitriding. The effect of the content of different elements (Cr, Mo, V, Si and Al) on the maximum hardness level and the nitriding depth was investigated. Reducing the silicon content enhances the nitriding performance, resulting in a higher nitriding depth or shorter nitriding duration. Aluminium reduces the nitriding depth slightly but leads to a strong increase in the surface hardness. Furthermore, aluminium significantly improves the thermal stability of the nitrided layer under operating conditions. The results can be used to aid the selection of hot-work tool steels and appropriate nitriding parameters.

Low Frequency Damping Behaviors of Magnesium Alloys

The effect of different alloying elements including Ni, Si and Al and various mass contents of these elements on the low frequency damping behaviors of magnesium alloys were investigated. The measurements of strain dependent and temperature dependent damping capacities of these magnesium alloys were carried out using dynamic mechanical analyzer (DMA), and the very different damping behaviors of these magnesium alloys were found. The hypoeutectic magnesium alloys with low solubility alloying elements such as Si and Ni shown extremely high damping capacities. But the Mg-Al alloys exhibited very low damping values. The tensile properties of these magnesium alloys were also illustrated in this study. It was found that hypoeutectic Mg-1.0%Si alloy possess the excellent overall properties with high damping capacity, relatively high tensile properties and good corrosion resistant ability.

Soundness of spray formed disc shape tools of hot-work steels

Abstract This paper presents metallurgical factors causing porosity in the spray formed die inserts and the corresponding solutions. High quality die inserts can be produced by spray forming if a good control of deposition parameters and the sprayed material is assured. Mechanism of the pore formation is discussed. Deoxidation of the melt at tapping for porosity reduction is found to be very difficult because it causes great variation in viscosity of the melt so that the process is difficult to control. Often the tundish nozzle is also blocked or frozen. Modification of the steel composition is found to be an effective method to improve the soundness of the deposition. Effects of different alloying elements on the soundness of the deposition are discussed. Especially influential on improving the soundness is the increased alloying of high temperature carbide-forming elements such as vanadium. A new series of hot-work steels is developed for spray forming high quality tools, which have not only improved soundness, but also longer lifetimes than the conventional hot-work steels.

Modelling the effects of alloying elements on precipitation in ferritic steels

This paper reports a systematic study on the effects of different alloying elements on the precipitation of M23C6 particles in power plant steels using a modified modelling technique. MTDATA is used to calculate some of the thermodynamic parameters for the alloying system. The elements studied include tungsten, aluminium, silicon, manganese, cobalt, copper, nickel and molybdenum with varying degrees of concentration. Results show that all the elements are beneficial in reducing the coarsening rate of M23C6 precipitates at low concentrations. Coarsening rate decreases progressively with increasing concentration of Si, Co, Al and Cu. Ni can be very harmful by increasing coarsening rate when its concentration is greater than about 0.4 at.%. Both Mn and W are quite effective in reducing coarsening rate when the concentrations are low. Extremely sharp increases in coarsening rate are found when the concentrations of these two elements exceed about 0.5 at.%. Mo is significant in reducing the coarsening rate even at very low concentrations and the effect is more pronounced with increasing concentration. All these effects result from the change of solubility of chromium in the matrix caused by the alloying elements.

Effects of alloying elements on creep of TiAl alloys with a fine lamellar structure

Creep experiments were conducted on five powder-metallurgy TiAl alloys with fine grains (65–80 μm), fine lamellar spacings (0.1–0.16 μm), and different compositions [Ti–47Al (+Cr, Nb, Ta, W, Si)] at temperatures of 760°C and 815°C and stresses from 35 to 723 MPa. Results show that at a given lamellar spacing, replacing 1% Nb (atomic percent) with 1% Ta and replacing 0.2% Ta with 0.2% W induced little effect, but addition of 0.3% Si decreased the creep resistance by a factor of 3–4 under otherwise identical conditions. Field emission TEM was used to characterize the changes of microstructure and alloy element distribution before and after creep. It was found that thinning and dissolution of α 2 lamellae and continuous coarsening of γ lamellae were the main creep processes and the microalloying elements tended to segregate at lamellar interfaces, especially at ledges during creep. The effects of different alloying elements are interpreted in terms of the interaction of alloy segregants with misfit and/or misorientation dislocations at the lamellar interface. That is, the interaction retards the climb of interfacial dislocations and thus the creep process in the case of large segregants (Nb, Ta, W), but facilitates the climb and creep in the case of small segregants (Si).

Production of higher-quality galvanized pipe for land reclamation

The Voroshilovgrad Pipe Plant has mastered the production of spiral-welded steel pipes with a zinc coating for farm irrigation. In introducing this technology, the plant investigated the effect of different alloying elements (magnesium, aluminum, nickel, copper) introduced into the zinc melt on the corrosion resistance of the resulting coatings. Accelerated tests were conducted in a 3% aqueous solution of superphosphate and in artificial seawater, as well as in soil wetted varying amounts with seawater. The results showed that zinc coatings simultaneously alloyed with 0.050.15 AI and 0.05-0.3 Ni (wt.%) had the best corrosion resistance. Depending on the medium, the corrosion resistance of these coatings was 1.33-1.54 times greater than that of the unalloyed zinc coatings. 9 The data obtained made it possible to select a composition for the melt to be used in galvanizing pipes. Commercial galvanizing baths were alloyed with nickel by placing plates of nickel about the perimeter of the bath. Pipes were galvanized in the nickel-alloyed baths by the following regime: temperature 450 _+ 5~ time of immersion 25 sec; time of extraction 40 sec. The thickness of the coating was 80 #m, which met the requirements of TU 14-3-1001-81. Thus, it was discovered that microalloying galvanizing baths with micro-additions of other metals can improve the corrosion resistance of the latter. The above-described technology for pipe-galvanizing has been introduced at the Voroshilovgrad plant for galvanizing spiral-welded pipes. The use of pipes with an alloyed zinc coating increases the service life of the irrigation systems in which the pipes are used.