Arc Melting Route Research Articles

Rhombohedral phase high-entropy alloy of AlMnCuZnBi as a photo-Fenton catalyst for methyl orange degradation

The formation of solid solutions with five or more elements having nearly equiatomic contributions termed as high entropy alloys (HEA), is recent strategy for the development of new materials. Such alloys have displayed superior properties than the conventional ones. The prepared alloys are generally face- or body-centered cubic structures with a few exceptions for orthorhombic and hexagonal close packed structure. In this, we report the synthesis of HEA of AlMnCuZnBi having rhombohedral crystal structure. The material was prepared by vacuum arc melting route. Both the diffractions (X-ray and electron) confirm its structure. The calculated thermodynamic empirical parameters e.g. ΔSmix, ΔHmix, δ, VEC and Ω even validate the feasibility of this single phase solid solution. The HEA had shown feeble ferromagnetic behaviour. The rhombohedral structured HEA may open up new possibilities for various emerging applications. The proposed HEA acted as a catalyst for photo-Fenton like reaction and could degraded methyl orange dye completely in 170 minutes.

Effect of metalloid element on the microstructural and mechanical properties of AlCoCrCuFeNi high-entropy alloys

ABSTRACT The impact of the metalloid element silicon (Si) addition on the microstructural and mechanical properties of the AlCoCuCrFeNiSix high-entropy alloy system is examined in this paper. The alloys were synthesized using a vacuum arc melting route. X-ray diffraction was used to analyse the current high-entropy alloys’ phase formation to comprehend the alloying process’s behaviour. It is evident from the peak pattern of the X-ray diffraction that the inclusion of Si promotes the growth of body-centred cubic structures. The microhardness and wear resistance were increased by increasing the Si content from 0 to 0.9. Si presence enhances the hardness of the alloys and strengthens the grain boundary. Improved hardness and wear resistance results from the enhanced body-centred cubic-phase formation, which poses a barrier to the dislocation movement and prevents further deformation. Furthermore, the inclusion of Si improved corrosion resistance in potentiodynamic polarization measurements. Excellent compressive strength is possessed by all of the high-entropy alloys with Si addition.

Ceramic-reinforced HEA matrix composites exhibiting an excellent combination of mechanical properties

CoCrFeNi is a well-studied face centered cubic (fcc) high entropy alloy (HEA) that exhibits excellent ductility but only limited strength. The present study focusses on improving the strength-ductility balance of this HEA by addition of varying amounts of SiC using an arc melting route. Chromium present in the base HEA is found to result in decomposition of SiC during melting. Consequently, interaction of free carbon with chromium results in the in-situ formation of chromium carbide, while free silicon remains in solution in the base HEA and/or interacts with the constituent elements of the base HEA to form silicides. The changes in microstructural phases with increasing amount of SiC are found to follow the sequence: fcc → fcc + eutectic → fcc + chromium carbide platelets → fcc + chromium carbide platelets + silicides → fcc + chromium carbide platelets + silicides + graphite globules/flakes. In comparison to both conventional and high entropy alloys, the resulting composites were found to exhibit a very wide range of mechanical properties (yield strength from 277 MPa with more than 60% elongation to 2522 MPa with 6% elongation). Some of the developed high entropy composites showed an outstanding combination of mechanical properties (yield strength 1200 MPa with 37% elongation) and occupied previously unattainable regions in a yield strength versus elongation map. In addition to their significant elongation, the hardness and yield strength of the HEA composites are found to lie in the same range as those of bulk metallic glasses. It is therefore believed that development of high entropy composites can help in obtaining outstanding combinations of mechanical properties for advanced structural applications.

TiVCrNiZrFex High entropy alloy: Phase evolution,magnetic and mechanical properties

A series of TiVCrNiZrFex (0 ≤ x ≤ 10) high entropy alloys were synthesized via vacuum arc melting route and phase evolution in the alloy system was examined in the present study. With an increase in the Fe concentration, the phase changes from pure C14 Laves to a mixed (major body-centered + C14 Laves) phase.Interestingly, the lattice contraction takes place with an increase in Fe content. The C14 Laves phase reveals the paramagnetic nature, which changes to a dual magnetic phase, as the volume fraction of the Laves phase decreases due to the addition of Fe. The addition of Fe also significantly reduces the hardness, while the opposite trend is observed for elastic modulus. Several thermodynamical and topological parameters were estimated to establish their crucial role in controlling the Laves phase formation in the multicomponent systems. Notably, a new parameter, Mendeleev number difference (∆M), was introduced and discussed in the light of the present investigation. The results show that ∆M can prove to be quite useful for predicting the formation of type (FCC, BCC or HCP/Laves) of solid solution as well as designing the new HEA systems.

Effect of Cobalt Content on Thermal, Mechanical, and Microstructural Properties of Al0.4FeCrNiCox (x = 0, 0.25, 0.5, 1.0 mol) High-Entropy Alloys

Al0.4FeCrNiCox (x = 0, 0.25, 0.5, 1.0 mol) high-entropy alloys are developed by arc melting route to investigate the effect of cobalt content on thermal, mechanical, and microstructural properties. The phase, microstructure, and chemical composition are analyzed using x-ray diffraction, transmission electron microscope, and scanning electron microscope with attached energy-dispersive x-ray spectrometer. The obtained results have shown that the Al0.4FeCrNiCox (x = 0-0.5 mol) high-entropy alloys form a simple FCC + BCC-type solid solution and Al0.4FeCrNiCox=1 HEA forms a single-phase FCC structure. The compressive yield strength, microhardness, and thermal conductivity are observed to decrease from 965.22 to 233.37 MPa, 253.6 to 155.6 HV, and from 4.87 to 2.674 W/mK, respectively, whereas the electrical resistivity is observed to increase from 150.30 to 273.74 µΩ-cm with the addition of cobalt from x = 0-1 mol. Differential scanning calorimetry analysis has indicated that the Al0.4FeCrNiCox (x = 0, 0.25, 0.5, 1.0 mol) high-entropy alloys are thermally stable up to 1000 °C.

Powder Metallurgy Synthesis of Heusler Alloys: Effects of Process Parameters.

Ni45Co5Mn40Sn10 Heusler alloy was fabricated with elemental powders, using a powder processing route of press and sinter, in place of vacuum induction melting or arc melting route. The effects of process parameters, such as compaction load, sintering time, and temperature, on the transformation characteristics and microstructures of the alloy were investigated. While the effect of compaction pressure was not significant, those of sintering time and temperature are important in causing or annulling martensitic transformation, which is characteristic of Heusler alloys. The processing condition of 1050 °C/24 h was identified to be favorable in producing ferromagnetic Heusler alloy. Longer durations of sintering resulted in an increased γ-phase fraction, which acts as an impediment to the structural transformation.

Comparison of Aluminum Based Alloys Reinforced with Intermetallic Developed by Powder Metallurgy and Arc Melting Routes

Abstract In this work, Al-Ti alloys were prepared using metallic powders of Al and Ti via Powder Metallurgy (PM) and Arc Melting (AM) route. Four chemical compositions including pure aluminum were studied. Metallic powders were mixed with three compositions, Al-5Ti, Al-10Ti and Al-10Ti-2SiC. All the compositions were in atomic percentage. In case of PM, samples were pressed uniaxially at 170 MPa to fabricate 10 mm diameter compacts followed by pressure-less sintering at 620°C under argon atmosphere for 4 hr. Pure Al showed densification up to 96% whereas sample with 5 at.% Ti decreased in densification to 90%. For samples with 10 at.% of Ti and with 2 at.% SiC, densification values were 92% and 93%, respectively. In the case of AM method, the process was carried out under vacuum in Argon atmosphere followed by homogenization at 600°C for 1 hr. The resulting microstructure and composition of samples were analyzed. X-ray diffraction (XRD) results confirmed the formation of TiAl3 intermetallic phase in the alloy. The mechanical test used to assess samples performance was hardness. Hardness results showed a strong increase in hardness with increasing Ti contents and SiC addition for both types of samples. The developed Al-Ti and Al-Ti-SiC alloy exhibit better hardness properties and have the potential to be used for light-weight materials applications.

Effect of aluminum addition on the properties of CoCuFeNiTi high entropy alloys

This study investigates the effect of aluminum addition on the micro structural, corrosion and mechanical properties of AlxCoCuFeNiTi (x = 0, 0.25, 0.5, 0.75, 1 atom %) High Entropy Alloys which were prepared by Arc melting route. Addition of Al changes the microstructure of the alloys from FCC to a mixture of FCC and BCC phases. The corrosion behavior of the alloys in the 3.5 % NaCl solution and Red Fuming Nitric Acid is reported. Addition of 0.25 atom % Al improves the corrosion resistance of the high entropy alloys in both solutions, whereas higher fraction elevates the corrosion rate.

Ni tracer diffusion in CoCrFeNi and CoCrFeMnNi high entropy alloys

High entropy alloys (HEAs) are multicomponent alloys in equiatomic or nearly equiatomic composition. Anticipated sluggish atomic diffusion is reported to be one of the core effects in HEAs which is presumably responsible for their many unique properties. For the first time, in the present study, tracer (Ni) diffusion in CoCrFeNi and CoCrFeMnNi alloys is measured by the radiotracer technique in the temperature range of 1073–1373 K using the 63Ni isotope. Chemically homogeneous alloys of equiatomic composition were prepared by a vacuum arc melting route. The microstructure and phase stability of the alloys in the given temperature range is confirmed by differential thermal analysis and X-ray diffraction.Ni diffusion in both CoCrFeNi and CoCrFeMnNi alloys is found to follow Arrhenius behavior. When plotted against the homologous temperature, a tendency to a successive slow down of the tracer diffusion rate with an increased number of components in equiatomic alloys is unambiguously established. Both the entropy term as well as the energy barriers is revealed to contribute to this trend. The current results indicate that diffusion in HEAs cannot a priori be considered as sluggish.

FeAl Based Intermetallic Matrix Composites Through Melt Route

FeAl based composites reinforced by carbide particles have attracted much attention in the recent years. In the present study, FeAl based composites were prepared by using arc melting route in argon atmosphere. The Ti/Zr addition to FeAl based alloys containing carbon have produced in situ formation of second phase particles namely TiC/ZrC respectively. The in situ precipitated TiC/ZrC carbides were found to be thermally stable and improved the mechanical properties of FeAl. The influence of these alloy carbides on the mechanical properties of FeAl based composites were studied. The addition of Ti/Zr resulted superior strength than FeAl alloy containing carbon. The mean coefficient of thermal expansion (CTEs) of FeAl based composites were also measured. The presence of these carbides significantly affected the CTE of FeAl based composites.

Metallurgical characterizations of Fe–Cr–Ni–Zr base alloys developed for geological disposal of radioactive hulls

Alloy melting route is currently being considered for radioactive hulls immobilization. Towards this, wide range of alloys, belonging to Zirconium–Iron binary and Zirconium–Stainless steel pseudo-binary systems have been prepared through vacuum arc melting route. Detail microstructural characterization and quantitative phase analyses of these alloys along with interaction study between Zirconium and Stainless steel coupons at elevated temperatures identify Zr(Fe,Cr) 2, Zr(Fe,Cr), Zr 2(Fe,Cr), Zr 3(Fe,Ni), Zr 3(Fe,Cr), Zr 3(Fe,Cr,Ni), β-Zr and α-Zr as the most commonly occurring phases within the system for Zirconium rich bulk compositions. Nano-indentation studies found Zr(Fe,Cr) 2 and Zr(Fe,Cr) as extremely hard, Zr 3(Fe,Ni) as moderately ductile and β-Zr, Zr 2(Fe,Cr) as most ductile ones among the phases present. Steam oxidation studies of the alloys, based on weight gain/loss procedure and microstructural characterization of the mixed oxide layers, suggest that each of the alloys responded to the corrosive environment differently. Fe 2O 3, NiFe 2O 4, NiO, monoclinic ZrO 2 and tetragonal ZrO 2 are found to be most common constituents of the oxide layers developed on the alloys. Integrating the microstructural, mechanical and corrosion properties, ZrFeCrNi3 (Zr: 84.00, Fe: 11.20, Cr: 3.20, Ni: 1.60, in wt.%) is identified as the acceptable base alloy for disposal of radioactive hulls.

Development of powder metallurgy technique for synthesis of U 3Si 2 dispersoid

The Indian research reactor APSARA, which uses HEU based UAl 3 fuel dispersed in aluminium matrix, is to undergo core conversion to LEU based U 3Si 2 dispersoid in aluminium matrix fuel. Work has been initiated at BARC, to prepare uranium silicide (U 3Si 2) compound using powder processing route in place of vacuum induction melting or arc melting route. This paper describes the preparation flow-sheet of the U 3Si 2 dispersoid by an innovative powder processing route with uranium metal powder and silicon powder as starting materials.

Magnetic properties of Sm–Ru–B–C

A series of quaternary intermetallics having the nominal composition Sm(1)Ru( n)B( n)C(1), (designated as 1nn1 compounds, n=1, 2, 3 and 4), have been prepared by arc melting route. X-ray diffraction patterns reveal two types of compounds in the case of 1441 nominal composition. One has a bct structure ( a=7.484 Å and c=14.997 Å) with small amount of some impurity phases; another is a mixture of a bct phase ( a=7.485 Å and c=14.982 Å) and a hexagonal phase ( a=5.566 Å and c=2.944 Å) in the proportion 1:2. The observed phases resemble SmRu 4B 4 (bct, a=7.482 Å and c=15.049 Å) and SmRu 3B 2 (hexagonal, a=5.536 Å and c=2.997 Å). In SmRu 4B 4C, superconductivity around 12 K has been reported in the literature whereas no superconductivity is observed down to 4.2 K in any of our samples. Surprisingly, the 1221 and 1331 samples resulted in materials of essentially single phase with a hexagonal structure having lattice constants ( a, c)=(5.551, 2.976) Å and (5.569, 2.955) Å, respectively, which resembles that of SmRu 3B 2, but with distinctly different cell constants. They exhibit ferromagnetic order with T C ∼60 K and ∼50 K, respectively. At 5 K, they exhibit magnetic hysteresis with a very large coercive field H C of about 15 T. All the samples of 1111 nominal composition resulted in multiphasic materials and showed two weak magnetic transitions in the temperature range (50–70) K, and a prominent ferromagnetic transition below 4 K.

Microstructure and phase relations in a powder-processed Ti-22AI-12Nb Alloy

A systematic investigation was undertaken to compare the effect of processing on the phase relations and microstructure of 66Ti-22Al-12Nb (in at. pct) alloy. The alloy was processed by three different routes: (1) cold pressing (CP) followed by reaction sintering; (2) CP followed by hot pressing (HP) followed by sintering; and (3) arc melting (AM), hydride-dehydride processing to make the alloy powder followed by cold isostatic pressing and then sintering. The samples were analyzed by X-ray diffraction (XRD); optical microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and electron microprobe analysis (EPMA). The analyses showed that all the processing methods have resulted in the same phases, but the AM route resulted in an equiaxed microstructure, whereas the other two methods resulted in a lamellar microstructure. This refinement in microstructure was attributed to the hydride-dehydride processing step of the AM route.