Papers by Keyword: Alloying

Abstract: Extensive efforts have been undertaken worldwide to develop new high strength steels with substantial fractions of retained austenite, for lightweight automobile manufacturing and other applications requiring improved combinations of strength and formability. These “3rd Generation” Advanced High Strength Steels (AHSS) are being implemented, and spot-welding has been found to present new challenges for these steels when Zn-based corrosion resistant coatings are involved, wherein zinc liquid metal embrittlement (LME) can occur. Some recent work is highlighted here that was designed to examine the separate effects of prior microstructure and alloy composition on LME sensitivity. LME behavior was assessed by comparing hot-ductility of steels with and without a Zn coating tested under conditions simulating spot-weld thermal cycles. Effects of prior microstructure on LME susceptibility were assessed with a single AHSS alloy composition, using annealing modifications to produce martensitic, Q&P, TBF and dual-phase substrates. The dual-phase steel exhibited less sensitivity to LME, perhaps because the Zn penetration and cracking are unable to follow (prior) austenite boundaries in this microstructure. With respect to alloy composition, carbon and manganese variations did not lead to noticeable effects on LME sensitivity, while silicon clearly leads to increased LME sensitivity. Addition of 1.3 wt. pct. aluminum to a 0.5 wt. pct silicon-containing AHSS steel further increased LME sensitivity at some test temperatures. The effects of alloying are interpreted in terms of the propensity to form an intermetallic reaction layer that consumes liquid and physically separates the substrate and liquid zinc.

Abstract: In this work, the preparation and processing of aluminum-copper alloys, which added amounts of copper to aluminum in different parentages (2, 4, 5%) so that it does not exceed the saturation limit for aluminum (6% Copper). After adding these specific amounts of copper to aluminum, have been melting each alloy to thaw copper in aluminum fully and diffusion copper atoms in it, and after that the specimens were prepared and quenched at 8-30 hours and rapid cooling in the water, and then were studied parameters of heat treatment and different percentages of copper. It is clear from the schemes and experimental results that each weight ratio of copper in aluminum has a different approach to reach the best mechanical properties. After performing mechanical tests and tests, it was found that the highest hardness of the (aluminum-copper) alloy in the case of (2% Cu) amounted to (120 HB) and in the case of (4% Cu) the amount (211 HB) and in the case of (5% Cu) the amount (188 HB).

Abstract: The paper investigates the optical and photocatalytic properties of strontium bismuthate doped with various rare earth elements. The data presented indicate that the type and concentration of the dopant have different effects on such parameters of a given semiconductor photocatalyst, such as the optical bandgap, absorption in the intrinsic area, and photocatalytic activity. On the basis of the studies carried out, the most promising rare earth elements have been identified and their optimal concentrations have been established for doping alkaline earth metal bismuthates.

Abstract: In metallurgy production nickel is an important alloying element used in the production of stainless, heat-resistant, acid-resistant grades of steel. For the development of ferronickel production in the Russian Federation, it is proposed to involve in processing complex poor iron-chromium-nickel ores of the Khalilovskoye deposit, which are not used at the present time. In the frame of this work the dependences of the elements reduction degrees of iron-chromium-nickel ore on the iron extraction degree were studied. These dependencies are necessary for the choice of the composition and development of ferronickel production technology. Burned ore raw materials were subjected to a selective carbothermal reduction in the laboratory electric arc furnace. In the obtained ferroalloy the nickel content decreased from 65 to 3%, phosphorus - from 0.68 to 0.38%, sulfur - from 0.19 to 0.10% with an increase in the reducing agent consumption. With the reduction of 1% iron, the recovery of nickel was only 50%, with 5% - 65–75%, with 20% - 95%. The content of iron oxides in the partially reduced melt with an increase in coke consumption decreased from 61 to 53%, and nickel oxide - from 0.192 to 0.010%. The analysis of the dependences allows us to make a conclusion that it is inappropriate to recover less than 5% of iron due to the low degree of nickel recovery (less than 70%). The rational degree of iron reduction from ore raw materials is 5-10%, which corresponds to the nickel content in the ferroalloy 10-20%, phosphorus - 0.3-0.5%, sulfur - 0.08-0.09%. Obviously, the resulting crude ferronickel needs refining, first of all dephosphorization.

Abstract: One of the effective ways to improve the quality of semi-finished products made from aluminum alloys is to eliminate the columnar and fan-shaped structure in them, refine the grain and achieve homogeneity, is modification and alloying. Modification of the melt is carried out using ligatures and allows a significant increase in the casting rate without fear of an excessive increase in the degree of zonal segregation during crystallization, as well as ensuring the uniformity of the chemical composition over the section. An important role in the quality of modification is also played by the manufacturing technology of the master alloy itself, which should ensure an increase in the cooling rate during crystallization. To obtain an alloy with the required properties, the quality of the charge materials used must be considered. First of all, this concerns master alloys, which are used for alloying and modifying the alloy. The most common for the manufacture of ingots and shaped castings are master alloys containing boron or boron and titanium. The boron content in these ligatures is 1-5%. It is generally accepted that a large amount of boron (except for the rise in the cost of the alloy itself) upon accelerated cooling promotes the refinement of the internal structure of the grain, but can lead to an increase in large inclusions of TiB2.

Abstract: The dilatometer study of the austenite transformations in steels with different chemical composition was conducted. The studied steels were classified as the air hardened steels of different alloying systems (Cr-Ni-Mo, Cr-Mn-Si-Mo and Cr-Mo-V) designed for the mining applications (rock drilling equipment, drilling instrument). The microstructure of the steels was investigated after continuous cooling at the rates of 0.1...30 °C/s from the austenitization temperature down to the ambient temperature. The CCT diagrams of the studied steels were plotted showing that the alloying with different set of elements can provide the desired hardenability and microstructure.

Abstract: At present, casting and wrought high-strength and light aluminum alloys are widely used in the creation of a number of products and units in mechanical engineering, aviation and space technology. The process of developing alloys includes the formation of initial design data covering the operating conditions, the necessary physical, mechanical and other characteristics of products, and also considers the requirements of manufacturability in their manufacture and ensuring a given structure. To achieve these goals, when smelting aluminum alloys, Al-Mg, Al-Cu, Al-Mn, Al-B, Al-Ti ligatures are used. Despite the widespread use of ligatures, there is no single set of requirements for their quality. However, recent studies in the field of structural heredity in the "charge - melt - cast product" system have shown that the structure of the ligature has a significant hereditary effect on the crystallization process, structure and properties of the modified alloy. In this work, a study of the Al-5Ti-1B master alloy was carried out using synchronous thermal analysis, which made it possible to establish such properties as: the magnitude of the thermal effect, the temperature of its onset, enthalpy, and the crystallization interval. The results obtained make it possible to expand the bank of initial data to improve existing programs for modeling casting processes and to develop new ones.

Abstract: Commonly used Grade 20GL cast steel has unstable impact strength values determined on V-notched samples at –60 °C and so cannot provide reliability of cast parts at negative temperatures.

Abstract: The structure, phase and chemical composition of the diffusion interaction zone, formed at the interlayer boundary of a layered composite of the alloy Cr15Ni60-aluminum AD1, are studied. The temperature-time conditions for its nucleation and growth are determined. The diffusion zone has a fine predominantly heterogeneous structure and consists of solid solutions based on aluminides Al₃Ni, Al₃Ni₂ and Al₇Cr, as well as the ternary compound Al₅FeNi. It is shown that the intensity of diffusion zone growth at the interlayer boundary of the bimetal Cr15Ni60-AD1 is determined mainly by the heating temperature, and the dependence of its thickness on the exposure time obeys a parabolic law. The presence of chemical micro-inhomogeneity in the form of a melted metal at the interlayer boundary does not have a qualitative effect on the kinetics of the process: at the first stage, the diffusion zone repeats the contour of the fusion, and then, as the service time increases, «absorbs» it.

Abstract: The wear resistance and characteristics of the friction surface of metal coatings with nitride-boride alloying are investigated. The object of the study was the steel deposited with flux-cored wire containing 15% chromium, 0.5% boron nitride, 1.25% titanium di-boride and 0,5% zirconium di-boride. It was established that the average value of the relative wear per test was 0.00416 g/m, which is 1.8 times less than that of the coating metal without borides. The average value of linear wear was 0.0122 mm/m, which is 1,9 times less than that of the coating metal without borides. The average value of the friction torque for the entire friction path in 339 m was 20.96 Nm. The coefficient of friction was 0.425. The hardness of such a metal reaches a maximum value of 57 HRC. The micro-hardness of structural objects is for the matrix 617-648 HV, eutectic 764-847 HV and strengthening phases 1128-1247 HV. It is shown that the metal structure is an iron-chromium martensitic matrix with a eutectic component, formed on the basis of boride (Fe, Cr)₂B and high-strength nitride ε-(Fe, Cr)_2-3N, which is an effective obstacle to dislocation slip under conditions of plastic deformation of the surface at wear.