Melting Route Research Articles

Investigation on the reaction of sulphur with Ag–Cu–Zn-Ge alloy: Experimental and computational study

Silver and its alloys undergo tarnishing with time, which is a black stain on the surface due to the formation of Ag2S. Developing a tarnish resistant Ag alloy was attempted by alloying Ag with elements that form a passive oxide layer on the surface. Germanium is proven to provide better tarnish resistance to sterling Silver alloy (92.5 wt% pure) which is available under the trade name of Argentium©. The present work investigates the tarnish resistance behavior of sterling silver alloy (92.5 wt% pure) containing various additions of Copper, Zinc, and Germanium. The alloys were prepared by melting and casting route, followed by Passivation Heat Treatment (PHT) to create a stable and continuous oxide layer. The temperature for PHT was optimized using thermogravimetry analysis (TGA) of the alloys prepared. Accelerated tarnish test was carried out to investigate the tarnishing behavior of alloy samples obtained before and after PHT. The samples were characterized using XRD, SEM-EDX, and micro-Raman Spectroscopy. The change in reflectance of the samples after tarnish test is determined using UV–Visible reflectance spectroscopy. The mechanism behind the tarnish resistance was derived using Density Functional Theory (DFT) by comparing sulphur (S2) and Oxygen (O2) adsorption energies (BE) of the alloying elements. The lower value of S2 (BE)/O2 (BE) indicates better oxidation and tarnish resistance. The ratio ranges between 222 % (Pure Ag) and 132 % (for Ag-4.2Cu-2.8Zn-1.4Ge) and the p-p between Ge and O has contributed to the reduction in the ratio.

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.

Performance Assessment on the Manufacturing of Zn-22Al-2Cu Alloy Foams Using Barite by Melt Route

A barium-rich Celestine (Sr,Ba)SO4 concentrate from the primary Mexican ore production was used as a thickening agent to produce closed-cell Zn-22Al-2Cu alloy foams, while calcium carbonate was used as a foaming agent. The microstructure and mechanical properties of the foams were analyzed by optical microscopy, scanning electron microscopy, and compression tests, respectively. The Zn-22Al-2Cu alloy foams showed a typical lamellar eutectic microstructure, constituted by a zinc-rich phase (η) and a (α) solid solution that was richer in aluminum, while a copper-rich (ε) phase was formed in the interdendritic regions. The SEM micrographs show the presence of small particles and aggregates that are randomly scattered in the cell walls and correspond to unreacted calcite and Celestine–Barian particles, especially for the higher barite addition. The compressive curves showed smooth behavior, wherein the particles at the cell walls did not affect the foam’s compressive behavior. The trial containing 1.5 wt. % of BaSO4 and 1.0 wt. % of CaCO3 showed a higher energy absorption capacity of 5.64 MJ m−3 because of its highest relative density and lowest porosity values. The Celestine–Barian concentrate could be used as a foaming agent for high melt-point metals or alloys based on the TGA results.

Study of phase evolution, mechanical, and tribological behaviour of a novel β-phase strengthened Ti-alloy with Fe and Co alloying via a laser material deposition route

A new Ti64-Fe-Co alloy was studied via a laser-material-deposition method. Associated with high growth restriction factors, β-eutectoid (Fe, Co) alloying minimizes anisotropy (due to the prior columnar β-grain growth) in the laseradditive -manufacturing (AM) built Ti-parts along with enhanced properties. Fe alloying for Ti64 via laser-AM results in superior strengthening with reduced ductility, where a good combination of strength and elongation properties can be achieved for a Ti-Fe-Co system. However, studies on Ti-Fe-Co-based systems via laser processing are limited. Co possesses a similar electronic property as Fe and the Ti-Fe system accompanies further solute addition. The effect of Co alloying the Ti64-Fe system was investigated in this study via a pre-placed laser-material-deposition method. A Ti64–5Fe-5Co alloy was formulated referring to CALPHAD simulations, along with a Ti64–10Fe composition. The new Ti-alloys were fabricated via both the laser-material-deposition and conventional vacuum arc melting routes, and the characteristics of the fabricated samples were examined. XRD analysis shows the evolution of the β-Ti phase with Fe and Co alloying, which agrees with the thermodynamic phase simulation results. The corresponding SEM micrographs depicted a β-phase dominant matrix with α-dendrites, and the solidification path was discussed. Considerable grain refinement was obtained for the laser-deposited alloys compared to the arc-melted ones, with an improved hardness value twice that of the commercial Ti64. A reduced stiffness for the laser-deposited Ti64–5Fe-5Co was observed from the load-vs-displacement characteristics, indicating matrix softening with Co alloying, which might benefit the elongation properties. The studied Ti-alloy shows a 30 % improvement in the dry-sliding wear characteristic with reduced fretting and abrasion compared to the commercial Ti64. The studied Ti-alloys were located in the theoretical d-electron space and new (Bo) ̅-(Md) ̅ vectors were introduced. Further studies on this would help in extending the applicability of laser-AM-built Ti-components.

Preparation and mechanical properties of in-situ aluminum foam-filled SS304 corrugated tubes with metallurgical bonding

In this work, AlSi10Ca3Mg0.5 alloy foam-filled SS304 corrugated tubes (FFCTs) were prepared by melt route with surface modification of the tube substrate prior to in-situ foam filling. Results showed that successful metallurgical bonding can be achieved between aluminum foam and the tube with surface modification. Under quasi-static axial loading, the foam core within FFCTs were compressed densely from top to bottom in sequence, showing an axisymmetric deformation mode. Due to the enhanced bonding between the foam and the tube, FFCTs with surface modification demonstrated approximately ∼19 % increase in specific energy absorption compared to FFCTs without surface modification.

Laser powder bed fusion additive manufacturing of Ti6Al4V-matrix composite with outstanding hardness/strength: Microstructural evolution and performance enhancement mechanisms

Incorporation of transition-metal boride with excellent mechanical performance as a reinforcing phase, represents a promising approach to address the challenge of insufficient hardness/strength in Ti6Al4V alloys. Despite the common challenge of achieving homogeneous distribution and refinement of TMB, this study leveraged a novel strategy involving laser-induced in-situ synthesis and a greatly strengthened laser-molten-pool effect, to additively manufacture highly-dense Ti6Al4V-matrix composites reinforced with mono-dispersed TiB nanowires. This was achieved through selective laser melting route of laser powder bed fusion. Remarkably, the unique microstructural morphology of these composites characterized by the uniform dispersion of high-aspect-ratio reinforcing phases, boron dissolution into α-Ti grain boundaries of the Ti6Al4V matrices, and unified crystallographic coordination of gradient transitional layers, contributed to their superior microhardness and compressive strength compared to the counterparts even with the higher contents of reinforcing phases. This achievement was attributed to the synergistic effects of various morphological mechanisms including second-phase, grain refinement, and stress-transfer reinforcing/strengthening. This research provided new insights into the precise control of microstructural evolution in metal-matrix composites and the enhancement of their overall mechanical performance.

Additive Manufacturing of Biodegradable Molybdenum - From Powder to Vascular Stent.

Magnesium, iron, and zinc-based biodegradable metals are widely recognized as promising candidate materials for the next generation of bioresorbable stent (BVS). However, none of those metal BVSs are perfect at this stage. Here, a brand-new BVS based on a novel biodegradable metal (Molybdenum, Mo) through additive manufacturing is developed. Nearly full-dense and crack-free thin-wall Mo is directly manufactured through selective laser melting (SLM) with fine Mo powder. Systemic analyses considering the forming quality, wall-thickness, microstructure, mechanical properties, and in vitro degradation behaviors are performed. Then, Mo-based thin-strut (≤ 100µm) stents are successfully obtained through an optimized single-track laser melting route. The SLMed thin-wall Mo owns comparable strength to its Mg and Zn based counterparts (as-drawn), while, it exhibits remarkable biocompatibility in vitro. Vessel related cells are well adhered and spread on SLMed Mo, and it exhibits a low risk of hemolysis and thrombus. The SLMed stent is compatible to vessel tissues in rat abdominal aorta, and it can provide sufficient support in an animal model as an extravascular stent. This work possibly opens a new era of manufacturing Mo-based stents through additive manufacturing.

High-Pressure Torsion: A Path to Refractory High-Entropy Alloys from Elemental Powders

For the first time, the refractory high-entropy alloys with equiatomic compositions, HfNbTaTiZr and HfNbTiZr, were synthesized directly from a blend of elemental powders through ten revolutions of high-pressure torsion (HPT) at room temperature. This method has demonstrated its effectiveness and simplicity not only in producing solid bulk materials but also in manufacturing refractory high-entropy alloys (RHEAs). Unlike the melting route, which typically results in predominantly single BCC phase alloys, both systems formed new three-phase alloys. These phases were defined as the Zr-based hcp1 phase, the α-Ti-based hcp2 phase, and the Nb-based bcc phase. The volume fraction of the phases was dependent on the accumulated plastic strain. The thermal stability of the phases was studied by annealing samples at 500 °C for one hour, which resulted in the formation of a mixed structure consisting of the new two hexagonal and cubic phases.

Microstructural and electrochemical behaviour of severely surface-deformed 316L steel manufactured by conventional and selective laser melting routes

This study thoroughly examines the influence of conventional and selective laser melting (SLM) routes and surface mechanical attrition treatment (SMAT) on the microstructural and electrochemical properties of 316L steel. Compared to wrought specimens, the SLM specimens exhibit significantly smaller grains (∼41 vs. ∼83 µm) and higher dislocation density (∼7.2 × 1013 vs. ∼3.7 × 1012 m−2). Both specimens show nearly doubled surface hardness after SMAT, with the SLM surface displaying a ∼30 nm grain size and minimal α’ phase. The microstructure significantly influences passivation and corrosion behaviour. The SLM specimens exhibit superior electrochemical characteristics to wrought counterparts in SMATed (0.00299 mmpy) and non-SMATed (0.00771 mmpy) conditions. SMAT effectively eliminates surface porosity, enhancing the passivation and corrosion resistance of SLM steel.

Refractory High‐Entropy Alloys Produced from Elemental Powders by Severe Plastic Deformation

A comparative investigation of two fundamentally different approaches for the synthesis, microstructure evolution, and mechanical properties of the refractory high‐entropy alloys (RHEA) HfNbTaTiZr and HfNbTiZr is performed. The two methods comprises conventional arc (button) melting and a powder route based on mechanical alloying and consolidation via severe plastic deformation. In particular, blended elemental powder is pre‐compacted and subjected to one or four passes of equal channel angular pressing (ECAP) at 500 °C and then 10 revolutions of high pressure torsion (HPT) at room temperature to an effective strain between 4 and 40. Some samples are then annealed at 500 °C for 1 h to investigate the thermal stability of the phases. The four ECAP passes at 500 °C do not result in the formation of the body‐centered cubic (BCC) phase typical for the program RHEAs despite the presence of interfacial zones between particles and defect‐driven diffusion. Nevertheless, a single ECAP pass is sufficient to create a solid bulk sample for subsequent HPT. After 10 HPT revolutions, in contrast to melting route resulting in a single BCC phase alloy, both alloys form new phases comprising a Nb‐rich BCC phase and a ZrHf‐rich HCP phase in both alloys.

Effect of Mn and Mg reinforcing particles on physico-mechanical behavior of close-cell Al metal foam for energy absorption material

A solid substance encircled by a three-dimensional network of voids not interconnected with each other is referred to as close-cell metal foam. The work is based on enhancing mechanical properties of aluminum base close-cell metal foam through the addition of reinforcing particles in varying percentages. Closed-cell aluminum foams with the addition of Mn (0.5 wt.%) and Mg (0, 1, 1.5, 2) were successfully prepared by the melt route method. Al-based metal foam’s morphology and mechanical behavior were examined in order to understand the impact of reinforcing elements. From the current work, it is inferred that the addition of reinforcing elements initially helped to increase the compressive strength as found in Foam-1, but further addition of Mg did not have any beneficial effects. It was found that the value of compression strength depends on foam density. The addition of reinforcing elements increases the length of the plateau which in turn increases the value of energy absorption. It is found that proper bonding of reinforcing particles helps in improving energy absorption. From the evaluation, it was found that besides the increase in density and variations in pores uniformity, Al + Mn (0.5wt. %) + Mg (1.5wt. %) Foam (Foam-1) was found to be superior among all other foams. It can also be concluded that by fixing the percentage of Mn by 1 wt%, the best results can be obtained by addition of 1.5 wt. % Mg in the melt. Further addition of Mg shows a detrimental effect on mechanical and physical properties.

Pore Structure and Deformation Correlation of an Aluminum Foam Sandwich Subject to Three-Point Bending.

An Al-Si matrix foam sandwich (AFS) with 6063 Al alloy cover sheets was fabricated by hot rolling combined with melt foaming. A foamable AlSiMg1/SiCp matrix precursor was prepared by the melting route. Hot rolling at 480 °C was carried out to obtain a mechanical bonding interface between the cover sheet and the foamable precursor. Meanwhile, the pore structure of the AFS was deeply affected by the foaming temperature and foaming time during the foaming process. Different pore growth mechanics of the crack-like pore disappearance mechanism (CDM) and pore active expansion mechanism (AEM) were concluded based on the pressure difference in pores inside and outside. Three bending tests were applied to three types of AFSs with different pore structures to evaluate the relation between pore structures and AFS mechanical properties. The bending property of the AFS with fewer layers of pores is like that of a dense material. The bending property of the AFS with a pore size in the range of 0~1 mm presents a typical sandwich shear failure mode. The AFS with a uniform pore structure, in which the shapes of the pores are predominately polygons and the pore diameter is concentrated in the range of 0.5~3 mm, processes a good energy absorption capacity, and the bending stress-strain curve fluctuates greatly after the first stress drop.

Систематический обзор технологий производства металлической пены

Introduction. The paper presents a comprehensive overview of the manufacturing methods, materials, properties, and challenges associated with cellular metallic foams, primarily focusing on aluminum and titanium-based foams. Cellular metallic foams are gaining interest due to its unique combination of low density, high stiffness, and enhanced energy absorption capabilities. Cellular metallic foam is renowned for its special combinations of physical and mechanical characteristics, containing their increased stiffness, specific strength at high temperatures, light weight, and good energy absorption at relatively low plateau stress. It has extensive uses in the automotive, shipbuilding and space industries. It has high porosity, low relative density and high strength, which increases performance of the product. The aerospace and automotive industries require a material with a high strength-to-weight ratio. Methods. To meet this need, many metal foam production methods have been developed, such as melt route method, deposition method and powder metallurgy method. Melt route method is widely used to manufacture metallic foam as compared to other methods. Results and Discussion. In the production of aluminum foams, the melt route method is usually used. Titanium hydride (TiH2) has been a popular foaming agent, but its high decomposition rate and cost limitations have led to the development of alternative foaming agents, such as CaCO3 (calcium carbonate). Titanium foam is often manufactured using the space holder method. This method involves mixing titanium powder with a space holder material, forming a preform, and then sintering to remove the space holder and produce a porous structure as the space holder method allows for precise control over the properties of the foam, including pore size, porosity, and relative density. Results also indicate that porosity in cellular metallic foams can range from 50 % to 95 %, as reported in various journals. Pore structures can include mixed types, open cells, and closed cells, each offering different mechanical and thermal properties. It is also observed from various literature sources that relative density, which is the ratio of the foam's density to the bulk material's density, varies from 0.02 to 0.44 based on the production method used.

The response of 316 L steel manufactured by selective laser melting route to high-temperature oxidation behaviour: The role of microstructure modification

The current work examines the effect of 316 L steel's microstructure, which is modified through varying scanning angles with the sample surface (HNS (0°), INS (45°), and VNS (90°)) in the selective laser melting (SLM) method and through surface mechanical attrition treatment (SMAT), on its high-temperature oxidation behaviour (at 600–800 °C) is investigated. We have obtained a deeper understanding of the steel's oxidation behaviour by applying various characterisation techniques. The SMATed steel has a ∼ 1000 μm thick deformed layer containing a gradient microstructure, and its topmost layer contains fine twins and nanograins (∼30 nm). The hardness of this surface is ∼1.65 times the non-treated steel's hardness. All samples follow a parabolic rate law during oxidation. The VNS sample unveils the slowest oxidation rate amid the non-treated samples. SMAT increases the activation energy of oxidation. The distribution of elements across the oxidised samples' cross-section shows discontinuous Cr spreading within the oxide layer on the non-treated samples; however, the deformed samples show uniform distribution. Unlike non-SMATed samples, a minute decline in Cr and Mn content is observed underneath the oxide layer on the SMATed samples, confirming their enhanced outward diffusion. The oxide layer on SMATed samples has more Cr- and Mn-rich oxides. These oxides occupy the grain boundaries of the oxidised non-SMATed surfaces, where the micro-pores and cracks are present. Conversely, oxidised SMATed surfaces display uniform, defect-free Cr- and Mn-rich oxides with finer grains. Moreover, the SMATed layer remains reasonably stable during high-temperature oxidation (hardness drop ranges between ∼9 and ∼ 30%).

PENGARUH PENAMBAHAN CACO3 DARI LIMBAH KULIT TELUR DAN WAKTU PENGADUKAN PADA PEMBUATAN ALUMINIUM FOAM MENGGUNAKAN METODE MELT ROUTE

Aluminum is a lightweight material that has good corrosion resistance and electrical conductivity. It can be used for making aluminum foam. One of the methods for making aluminum foam is the melt route method. Making aluminum foam using the melt route process, is called melting aluminum metal, adding foaming agent, and stirring. This study aims to determine the effect of adding CaCO3 from eggshells and stirring time on the foaming ability of aluminum foam. The characteristics that will be observed include the type of aluminum foam, height, pore size, density, porosity, and compressive strength. This research used the melt route method with adding variations in the mass composition of CaCO3 is 4, 5, and 6 wt% on smelted aluminum with stirring times of 30, 45, and 60 seconds. The process is carried out by heating aluminum to 760 °C and adding Al2O3 as a viscosity modifier then adding variations in the mass composition of CaCO3 and stirring with a variation of stirring time. The results show that the highest aluminum foam gets a value of 75 mm. The pore sizes of aluminum foam are obtained ranged from 0.287 to 1.109 mm. The optimal value obtained from the addition of CaCO3 with a mass composition of 4 wt% with a stirring time of 45 seconds, has a density value of 0.388 g/cm3, a porosity percentage of 85.848%, and a compressive strength of 1.777 MPa.

Compressive behavior and energy absorption analysis of casting skin-wrapped aluminum foams

The mechanical properties are an indispensable factor affecting the energy absorption capability of aluminum foam. In the past few decades, various aluminum foam sandwich structures, including casting skin-wrapped aluminum foams (CWFs), have been developed and proven to be effective in enhancing the integral mechanical properties. This study investigates how adding casting skin affects the compressive behavior and energy absorption of closed-cell aluminum foam. The aluminum foams were produced using the melt route and then used as the core material for manufacturing CWFs through counter-gravity casting solution after pre-heating. Axial and radial compressions were applied to columnar CWFs with pores falling within two size ranges and three ratios (D/T) of outer diameter to casting skin thickness. The failure mode of CWFs was dominated by brittle fracture of casting skin and progressive crush of foam core. Adding casting skin significantly enhanced the mechanical properties in axial compression, while it had no significant effect in radial compression, with both types of compression varying depending on D/T values. Samples with smaller pore sizes exhibited better overall performance. The influence of the addition of mass on the specific energy absorption should be considered in the design of lightweight crashworthy components.

Topotactic transition of Ti4AlN3 MAX phase in Lewis acid molten salt

MAX phases and its derived two-dimensional MXenes have attracted considerable interest because of their rich structural chemistry and multifunctional applications. Lewis acid molten salt route provides an opportunity for structure design and performance manipulation of new MAX phases and MXenes, Although a series of new MAX phases and MXenes were successfully prepared via Lewis acid melt route in recent years, few work is explored on nitride MAX phases and MXenes. Herein, a new copper-based 413-type Ti4CuN3 MAX phase was synthesized through isomorphous replacement reaction using Ti4AlN3 MAX phase precursor in molten CuCl2. In addition, it was found that at high temperature Ti4N3Clx MXene will transform into two-dimensional cubic TiNα nanosheets with improved structural stability.

Production of Refined and Modified Closed-Cell Aluminum Foams by Melt-Foaming Method

Closed-cell A356 aluminum alloy foams refined and modified were successfully fabricated by using barite and calcium carbonate as thickening and foaming agents, respectively. A melt treatment consisting of adding master alloys of Al-5Ti-1B and Al-10Sr for refining the dendritic microstructure and modifying the primary eutectic silicon, respectively, were included in the foaming process. The microstructure and mechanical properties of the foams manufactured were analyzed and compared with foams produced without the refining and modifying treatments. The secondary dendritic arm spacing (SDAS) was determined by optical measurements. Lower SDAS values were obtained in foam regions closer to the mold walls due to the high solidification rate imposed during the cooling step and a decrease in the SDAS values for the foams produced with the addition of the Al-5Ti-1B master alloy was evident. Additionally, the addition of the Al-10Sr master alloy caused the formation of solid solution dendrites and a fine irregular fibrous form of silicon. Foams produced with the melt treatment exhibit a good combination of structure and mechanical properties. Therefore, the melt route established is a feasible way to improve foam performance where the lowest SDAS and the highest mechanical properties were obtained for the closed-cell foams produced.

Very high-cycle fatigue performance of high carbon-chromium bearing steels with different metallurgical qualities

This study aims to explore the very high cycle fatigue performance of GCr15 bearing steel produced by two different melting routes by ultrasonic fatigue testing. The results show that the fatigue strength of the steel fabricated by continuous casting is still slightly lower (∼4%) than that of the steel by electroslag remelting route mainly due to the difference of their inclusion characteristics. The nitride is more detrimental to fatigue performance mainly due to its internal cracking mode and lower threshold value for granular bright facet formation. Compared with other GCr15 steels in literature, the tested steels exhibit excellent fatigue performance.