Alloy Additions Research Articles

Evolution Mechanism of Inclusions in H13 Steel with Rare Earth Magnesium Alloy Addition

Evolution Mechanism of Inclusions in H13 Steel with Rare Earth Magnesium Alloy Addition

Study of combined effect of zirconium and titanium on microstructure and mechanical properties of micro-alloyed cast steels

Aim of the present work is to study the influence of zirconium as well as titanium in combinations on the microstructures and mechanical properties of low carbon micro-alloyed cast steels and to compare with non micro-alloyed low carbon steels. The quantum of research work on the zirconium bearing micro-alloyed steels with respect to grain refinement and mechanical properties is scanty. The micro-alloyed steels with 0.05 wt% to 0.10 wt% Zr and Ti were melted by a conventional air induction melting furnace and they were further subjected to normalizing at a temperature of 1000 °C for 1 h followed by cooling in atmospheric air. The metallurgical properties of the heat treated samples were observed by optical microscope and TEM. It is observed that steel with Zr and Ti shows the presence of acicular ferrite with a very fine grain size of around 5–10 microns as compared to the non micro-alloyed steel. In addition, the inter-lamellar spacing of pearlite as well as presence of intermetallic compounds were seen clearly in the heat treated samples by TEM. It is also observed that the presence of precipitates accounts for the improvement of strength and toughness of steels containing micro alloying content in the heat treated condition. The steel with 0.1 wt% Zr + 0.1 wt% Ti content showed tensile strength with nearly two times higher in comparison to steel without micro alloy addition in steel. However the elongation of both steels is almost equal (percentage of elongation is found to be around 36%). This can be attributed due to the presence of zirconium carbo-nitrides causing the formation of fine grains in steel with Zr and Ti contents.

Effect of Grain Refiners and/or Modifiers on the Microstructure and Mechanical Properties of Al-Si Alloy (LM6)

Grain refinement is one of the most important and popular melt treatment process for Al-Si alloy casting. Microstructure and mechanical properties of commercially available Aluminium Silicon alloy LM6 can be improved with the addition of grain refiners and modifiers as these provide technical and economic advantages. This paper is an effort to study the effects of addition of grain refiners and modifiers to the eutectic Al – Si alloy LM6. Commercially available Al - Si alloy LM6 (eutectic = 12% Si) is grain refined with Al-5Ti-1B and Al-3B; and modified with Al-10Sr master alloys. These were added individually and then tested for its unique mechanical properties such as ultimate tensile strength, hardness and wear; which are co-related with the machining tests such as turning, surface roughness and drilling. The test results are compared with microstructure of the samples observed through SEM.The mechanical properties of this alloy can be altered after addition of master alloys, which in turn alter the grain size. Thus the results conclude that the mechanical properties of Al-Si alloys in general are controlled by a number of principal microstructural features. A fine grain size is desirable, leading to improvement of mechanical properties.

Application of thermal analysis in solidification pattern control of La-inoculated grey cast irons

The new generation of acid-lined medium-frequency coreless induction furnaces revolutionized the iron foundries, resulting higher overheating and lower S and Al content iron melt, characterized by higher eutectic undercooling solidification and consequently high chill [carbides] and unfavourable undercooled graphite morphologies sensitiveness. Having established that Al, Zr, Ti, Ca, Ba and La appear to have a key role in graphite nucleation in grey cast iron, thermal [cooling curves] investigations are undertaken to explore their effects on solidification parameters. The experimental heats are obtained in acid-lined coreless induction melting. Some important active elements are added to FeSi-based alloy, usually used as conventional inoculant in cast iron foundry industry, resulting complex inoculating systems [Al, Ca–La; Al, Ca–La, Zr; Al, Ca–La, Ba; Al, Ca–La, Zr, Ba; Al, Ca–La, Zr, Ti and Al, Ca–La, Zr, Ba, Ti]. In-mould [ceramic cup, cooling modulus of approximately 0.75 cm] inoculation is applied directly in the Quik-cup™ cooling curve analysis equipment, for the same alloy addition rate. The La effects are evaluated in low S and Al, high overheated electric grey iron solidification pattern with and without any other oxide-sulphides forming elements contribution. Study is focused on the representative temperatures during eutectic reaction and at the end of solidification, and it results in an undercooling referring to equilibrium eutectic temperature in the stable and metastable solidification system. As primary evaluation for general application, La, Ca, Al–FeSi alloy have a high efficiency in low S and Al and higher carbon equivalent grey cast irons, electrically melting, without any other active elements contribution. For specific applications, more complex La-bearing alloys are recommended, such as for higher dendritic austenite amount promotion [LaBaZrTi–FeSi alloy] or for lower eutectic recalescence [LaBaZr–FeSi alloy].

Influences of Al–20Si–2.5Fe–2Mn Master Alloy Additions on the Microstructure and Mechanical Properties of Hypereutectic Al–20Si Alloys

A novel Al–20Si–2.5Fe–2Mn master alloy containing α-Al15(Fe, Mn)3Si2 particles was developed to modify Si phases of hypereutectic Al–20Si alloy. The microstructure of as-cast specimens was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with energy-dispersive spectrometers (EDS), electron probe micro-analysis (EPMA), and X-ray diffraction (XRD). The morphology of primary Si phases changed from coarse irregular pentagonal and polygonal shapes to fine blocky shapes as the adding content of the master alloy increased up to 6.0%. The mean size of the primary Si phases decreased by 70.3% from 118 to 35 μm. Moreover, the shape of eutectic Si structure changed from coarse flakes or acicular shape to fine fibrous structure and granular particles. Furthermore, the Si phases were refined and homogenized when 6.0% master alloy was added into Al–20Si alloy. The optimum elongation (El) increased by 45.8% from 0.85 to 1.24%, and the optimum ultimate tensile strength (UTS) increased by 34.6% from 130 to 175 MPa comparing with unmodified Al–20Si alloy. In addition, the refinement and modification mechanisms of Si phases are also discussed on the hypereutectic Al–20Si alloys with the addition of master alloy.

Effects of graphite addition and air exposure on ball-milled Mg–Al alloys for hydrogen storage

Magnesium hydride (MgH2) is a promising candidate as a hydrogen storage material. However, its hydrogenation kinetics and thermodynamic stability still have room for improvement. Alloying Mg with Al has been shown to reduce the heat of hydrogenation and improve air resistance, whereas graphite helps accelerating hydrogenation kinetics in pure Mg. In this study, the effects of simultaneous Al alloying and graphite addition on the kinetics and air-exposure resistance were investigated on the Mg60Al40 system. The alloys were pulverized through high-energy ball milling (hereinafter HEBM). We tested different conditions of milling energy, added graphite contents, and air exposure times. Structural characterization was conducted via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). H2 absorption and desorption properties were obtained through volumetry in a Sieverts-type apparatus and Differential Scanning Calorimetry (DSC). The desorption activation energies were calculated using DSC curves through Kissinger analysis. Mg60Al40 with 10 wt% graphite addition showed fast activation kinetics, even after 2 years of air exposure. Graphite addition provided a catalytic effect on ball-milled Mg–Al alloys by improving both absorption and desorption kinetics and lowering the activation energy for desorption from 189 kJ/mol to 134 kJ/mol. The fast kinetics, reduced heat of reaction, and improved air resistance of these materials make them interesting candidates for potential application in hydride-based hydrogen storage tanks.

Effect of Chemical Composition on the Microstructure and Tribological Properties of Sn-Based Alloys

This article presents the test results of two bearing alloys on a tin matrix, differing in the content of alloy additions. Microscopic tests were performed using scanning electron microscopy, along with Brinell hardness tests and tests of tribological properties in the conditions of technical dry friction and wet friction using a TU-32 oil. Additionally, wear mechanisms were analyzed depending on the process conditions. The results indicate better tribological properties of the B82 alloy, with a higher content of antimony compared to the B89 alloy. This alloy contains more precipitates of hard phase β—SnSb, which both influence the level of the mechanical properties and determine the tribological properties. Additionally, it was proven that using the TU-32 oil as a lubricant practically eliminates adhesive wear, and the post-friction surfaces for both alloys are of a similar nature.

Design of a new Al-Cu alloy manipulated by in-situ nanocrystals with superior high temperature tensile properties and its constitutive equation

AlCu alloys inoculated by in-situ nano-sized particles crystallized from Ni-Nb-Ti amorphous alloys were prepared by casting method in this work. Different compositions of Ni-Nb-Ti amorphous alloys significantly enhanced heterogeneous nucleation for α-Al and promoted obvious grain refinement of the AlCu alloys. It was found that 0.05 wt% Ni-Nb-Ti amorphous alloys addition caused a significant and efficient refinement on α-Al (from 200 μm to 39 μm) and θ′ phase (from 146.4 nm to 37.6 nm). The strength and ductility of the inoculated alloy were improved significantly at high temperature. The tensile strength and fracture strain of the alloy inoculated by 0.05 wt% Ni-Nb-Ti amorphous alloy for 20 min at 533 K under the strain rates of 10−1 s−1 were increased by 32.63% and 90.35% respectively, compared to those of the uninoculated alloy. The nano-sized NiTi particles contributed to the grain refinement of α-Al, and grain refinement shortened the solute atomic diffusion distance and refined θ′ phase during heat treatment, resulting in higher strength and plasticity at high temperature. The model developed for this new type AlCu alloy is found to be efficient in predicting the stress at 453 K–533 K under the strain rates of 10−4 s−1 to 10−1 s−1.

Anisotropic nanocomposite Nd-Fe-B magnets produced by hot deformation with assistance of Nd-Cu

Abstract Uniaxial compressive deformation at elevated temperatures was applied to various Nd-lean Nd-Fe-B nanocomposite magnets. Particularly, influences of addition of eutectic Nd-Cu alloys having low melting points on texturing were investigated. X-ray diffraction and magnetic property measurements were carried out for the deformed samples to check whether texture is induced. A series of the experiments clearly demonstrated that no texturing occurs in the case of the alloys without any Nd-Cu alloy while textured magnets are successfully obtained when Nd-Cu is added. However, the texture obtained by the current attempt was not very strong. Detailed multi-scale electron microscopy revealed that the textured region was limited to where Nd was enriched and α-Fe phases disappeared. The strategy to obtain an ideal microstructure of nanocomposite magnet is discussed.

Effect of Fe-C alloy additions on properties of Cu-Zr-Ti metallic glasses

The effect of Fe-C alloy additions on thermal, mechanical and corrosive properties of (Cu50Zr40Ti10)1-x(Fe-C)x (x = 0–2.20 at%) alloys were systematically investigated. The results show that the Fe and C additions can enhance glass transition temperature Tg and onset crystallization temperature Tx, but narrow supercooled liquid region ΔTx. Work-hardening can be clearly observed for the Cu-based bulk metallic glasses (BMGs) containing Fe and C elements. The yield strength (σy), fracture strength (σf) and plastic strain (εp) are drastically increased by Fe-C alloy additions. The corrosion potential Ec increases and the corrosion current density ic decreases with increasing Fe and C contents. The studied Cu-based BMGs exhibit unique and novel anodic polarization behavior characterized by current platforms plus current serrations. The current serrations are much larger for the Cu-based BMGs with 0 ≤ x ≤ 1.32 at% than for those with 1.76 ≤ x ≤ 2.20 at%. The corrosion surface images are changed from the pits to the passive films by Fe-C alloy additions. The corrosion behavior gradually transforms from the pitting corrosion to the self-passivization with increasing Fe and C contents. The corresponding mechanisms are also discussed.

High temperature oxidation of Ni alloys in CO2 containing impurities

Next-generation power systems require structural alloys resistant to high-temperature oxidation in CO2 containing combustion impurities. Here we evaluate the oxidation performance of several commercial Ni alloys exposed to 95%CO2-4%H2O-1%O2, with/without 0.1% SO2, at 750 °C and 1 atm. All alloys formed protective chromia layers and showed no signs of carburization or sulfidation, and minimal chromia volatilization. The microstructural evolution of the alloy surface, secondary oxidants, and minor alloy additions all played a role in promoting protective chromia formation/growth. The results show that Ni alloys are promising candidates for high-temperature portions of next-generation CO2-based power systems.

Наукоемкая технология получения композиционных порошков в магнитовибрирующем слое

The paper reports the analysis of a problem current state connected with manufacturing high-quality composite powders. There is offered a device which allows obtaining a high uniformity of alloy addition distribution under conditions of a magnetic vibrating layer, and also metal polymeric composite powders. A designed model allowing the definition of a gradient interval of magnetic field induction is obtained, at which powder cluster destruction takes place and powder stable magnetic boiling is supported.

Electrodeposition of Co-W Coatings from Acidic-Citrate Solutions for Hydrogen Evolution

The electrochemical deposition of cobalt binary alloys with transition metals has received recently much attention due to some characteristic properties and possible practical applications of the coatings. These alloys, besides useful mechanical properties, exhibit valuable features like high corrosion resistance and low overpotential for hydrogen evolution reaction. Among many possible used alloy additives, tungsten seems to be the most promising to improve the catalytic and anti-corrosive properties of cobalt. Furthermore, the electrochemical method of coatings deposition features many advantages compare to other methods, even though the tungsten electrodeposition is very difficult due to its complex chemistry. It is still remains a challenge for many scientists to choose the optimal electrolyte composition and optimal parameters of the electrolysis process to obtain the cobalt alloy with the highest tungsten content. The present work aims to deposit of thin layered active cobalt alloy cathodes for hydrogen evolution. Electrodeposition mechanism and kinetics of cobalt and tungsten from acidic – citrate solutions was studied by electrochemical methods. In the present investigation, the composition of the electrolyte, potential and current density were changed systematically in ranges within which they significantly affect on the composition and structure of the resulting Co – W alloy. The proper adjustment of the process of electrolysis has a crucial role on the composition and structure of the deposited films, which decide about their electrocatalytic properties. The presence of cobalt and tungsten were confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy. Next the electrochemical properties of the coatings were examined in sulfuric acid and sodium hydroxide solutions. This work was supported by the Polish National Centre of Science under grant UMO-2016/21/B/ST8/00431. The authors would like to acknowledge the COST MP1407 Action for networking.

Numerical simulations of liquid steel alloying in the three strand continuous casting bloom tundish

This paper aims to obtain fundamental information on chemical homogenisation process of liquid steel with alloy additions in the bloom tundish. For alloy feeding to liquid steel pulse step alloying method was applied. Author checked the effect of hydrodynamic conditions occurs in the internal working space of tundish on the process of alloy mixing with liquid steel. Within the work basic and proposed tundish equipments were considered. Numerical modelling technique was employed to demonstrate the process of alloy addition mixing during continuous casting process. Ansys-Fluent computer program was used for numerical simulation. For particular continuous casting strands time mixing was calculated.

Prediction of Carbide Precipitation Using A Combined Partial Equilibrium - Para-Equilibrium - Lever Rule Approximation in Automobile Gear Materials

The carbide precipitation nature of an automobile gear material, i.e. Fe-C-Mn-Si-Cr-Mo alloy, during carburization and element addition process are investigated through PE+PA+LR prediction. Results show that, carburization process greatly increases the amount of cementite as well as the hardness index at the surface part. Besides, the addition of Ti and V helps to formation of TiC and (V, Mo)C carbides but suppress the precipitation of cementite, which contributes equivalent hardness at surface and lighter weight to the alloy.

Influence of Alloy Additions on the Microstructure, Texture, and Hardness of Low-Pressure Cold-Sprayed Al-Cu Alloys

This paper examines a series of Al-Cu binary alloy coatings, ranging from 2 to 5 weight percent copper, produced using low-pressure cold spray (CS) deposition with helium as the carrier gas. Binary Al-Cu alloy feedstock powder was produced through inert gas atomization and was sprayed over a variety of temperatures and pressures. Using helium gas, this set of Al-Cu alloys was successfully deposited as high-density coatings. Raising the carrier gas pressure increased the particle velocity and deposition efficiency (DE) in the case of spraying the Al-5 wt.% Cu powders. A clear composite deformation structure was formed in all coatings with clear prior particle centers surrounded by severely deformed regions with ultrafine grains. Microstructural deformation generated by the CS process produced a weak but clear fiber texture for both Al-2 wt.% Cu and Al-5 wt.% Cu coatings. The copper content of the feedstock powder directly influenced the coating hardness and porosity, while having no systematic effect on the DE.

Stability analysis of the Cold Metal Transfer (CMT) brazing process for galvanized steel plates with ZnAl4 filler metal

In order to achieve lower CO2 emissions and lower fuel consumption, modern motor vehicle industries have been reducing automotive weight with an increasing degree in the past years by replacing steel structures with brazed and welded components of steel and lightweight metals. In this context, the combination of galvanized steel and aluminum admits considerable application potential. Joints of the two cited different types of materials can be produced by partial brazing, through the Cold Metal Transfer (CMT) process with addition of zinc-based wire alloys. However, stability analysis for this process is still not well understood. Most papers focus on metallurgical characteristics such as intermetallic phase formation and joint strength. In order to assess stability, bead on plate samples made of ZnAl4 deposits on an automotive DX56D + Z140 galvanized steel was statistically correlated to current and voltage oscillograms as well as high-speed images, after variation of the IBoost parameter from 30 to 150 A. Short-circuit and arc burning times were acquired and used to compute the Vilarinho Regularity Index for Short-Circuit Transfer (IVsc), which is based on variation coefficients. The lower the IVsc, the more stable is the metal transfer. The index was used to assess bead homogeneity. The results pointed that bead homogeneity was found only for IBoost values below 97 A. However, stability was reached for IBoost levels of 97 A (with homogeneous bead) and 150 A (without homogeneous bead). This means that to determine homogeneity, the metal transfer stability, determined through IVsc, is an indicator, but other factors such as current level and its effects over the melt pool must also be considered.

Dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets

In this paper, dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated. It shows that the maximum energy product (BH)max and coercivity Hcj of Ce-Fe-B sintered magnet are improved from 6.76 to 9.13 MGOe by 35.1%, and from 1.44 to 1.67 kOe by 16.0%, respectively, via adding 5 wt% liquid phase alloy of Ce35.58Fe57.47Cu6B0.95 (at%). Compared with the magnet without Ce-rich alloy addition, the volume fraction of the grain-boundary phase with low melting point increases in the magnet with Ce-rich alloy addition, which is beneficial to improving the microstructure and promoting the coercivity enhancement of the magnet. In the Ce-Fe-B magnet with Ce-rich alloy addition, Cu and Ce enrich in the grain boundaries of the magnet after annealing, therefore the as-annealed magnet has a higher coercivity than the as-sintered magnet. A distinct Fe-rich layer with the average thickness of 60 nm is found in the grain boundaries in the magnet without Ce-rich alloy addition, but it seems that Fe-rich phase disappears in the magnet with Ce-rich alloy addition. The present work suggests that the further improvement of coercivity in the Ce-Fe-B sintered magnets is expectable by designing the composition and structure of added liquid phase alloys.

Microstructure and thermal/mechanical properties of hot-extruded aluminum/graphite composites with Al–Si alloy addition

Al/graphite composites with small amounts of Al–Si alloy were consolidated by spark plasma sintering and hot-extrusion processes. The effect of Al–Si alloy addition on densification behavior, microstructure, thermal conductivity (TC), coefficient of thermal expansion (CTE), and compressive strength has been systematically investigated. The results showed that the addition of Al–Si alloy resulted in improvements in relative density of the composites, interfacial bonding between Al and graphite, and orientation degree of graphite. The composites with Al–Si alloy showed improved TC and reduced CTE values in comparison with those without Al–Si alloy. For example, the 450 °C-extruded Al/60 vol% graphite/9 vol% Al–Si composite showed a maximum TC of 297 W m−1 K−1 and a minimum CTE of 7.95 ppm K−1. Moreover, the hot-extruded Al/graphite composites containing Al–Si alloy exhibited higher compressive strength compared to conventional squeeze-cast composites and hot-extruded composites without Al–Si alloy.

Effect of cobalt alloy addition in erosive wear and cavitation of coatings welds

The gas metal arc welding (GMAW) process is employed for coating when speed and high efficiency are required. Cold-wire GMAW is a variation of this process, in which an extra wire is introduced into the electric arc and/or the molten puddle. Parameter adjustment in this process is difficult, because it involves twice as many independent parameters as conventional GMAW. Improved mastery of this technology and its variables is essential for furthering its industrial use broadening its range of industrial uses for application of coatings. In this study, the impacts of cold-wire GMAW process variables on the fillet weld and alloy resistance to wear by pure erosion and cavitation were evaluated. A filler metal was deposited on Stellite™ 6 and 21 cobalt alloys on ABNT 1020 carbon steel sheets in the horizontal position. Coating wear was characterized through analysis of hardness and surface topography. The resulting cobalt alloys exhibited superior erosion resistance. Strengthening of Stellite 21 was verified with the pure erosion assay, while strengthening of Stellite 6 was established with the cavitation assay. Use of multiple wires during welding processes was shown to be necessary to obtain alloy combinations with superior resistance to the combined erosion-cavitation phenomenon.