Solidification Of Alloys Research Articles

Precipitation behavior of Al2CuLi, Al3Li and Al3Zr in A2060 aluminum-lithium alloys and mechanical behavior of their microinterfaces

The precipitated phase of Al-Li alloy is a major factor determining the properties of Al-Li alloy. Al2CuLi phase(T1 phase), Al3Li phase and Al3Zr phase are all important enhanced precipitated phases. In this paper, the properties of the matrix, the precipitated phase and the interface formed between each phase are calculated. The (111) crystal face of Al, (111) of Al3Li, (111) of Al3Zr, and (210) of Al2CuLi are the surfaces with the lowest surface energy of these phases. Al3Li/Al3Zr has the lowest interfacial energy (0.01961ev), so its thermodynamic stability is the best. The interface with the maximum bonding strength is the interface of Al3Zr/T1, and its adhesion work is 0.61878ev. A2060 aluminum-lithium alloy was thermally insulated at 580 °C for 2h and then hot rolled. After hot rolling, it was cooled to room temperature for cold rolling. Then the samples were treated with solid solution and aging, and different cooling methods were selected to obtain four kinds of samples: non-heat treatment, aging, air cooling and water quenching. It is found that the strength and hardness of Al-Li alloy are determined by the grain thickness of precipitated phase, and the ductility and hardness of Al-Li alloy are determined by the number of precipitated phase and the degree of dislocation density.

Formation of seaweed morphology and enhancing mechanical properties of an A356 alloy by directional solidification

In the present work, regular dendrite and seaweed pattern are produced by controlling the crystal orientation during directional solidification of an A356 aluminium alloy. These morphologies and growth orientation were investigated by electron backscatter diffraction (EBSD), and the results showed that the seaweed pattern mainly prevailed under the (100)[011] orientation. At the same time, the effects of seaweed pattern in the properties of A356 alloy were analysed by room temperature tensile test. It was found that the elongation and toughness of the samples reached 20% and 36J/m3, respectively, for the seaweed; 13% and 24J/m3, respectively, for the regular dendrites; and 8% and 14J/m3, respectively, for the cast ingot. Compared with the regular dendrite samples, the seaweed pattern obtained relatively excellent elongation and toughness. By using scanning electron microscopy (SEM), it is found that the distribution of eutectic silicon particles in seaweed morphology sample is more refined and uniform, which is the main reason for these enhancements.

A quantitative study of the solute diffusion zone during solidification of Al-Cu alloys via in-situ synchrotron X-radiography and numerical simulation

The solute diffusion zone plays a critical role in determining nucleation efficiency during heterogeneous nucleation. In this study, in-situ synchrotron X-radiography and numerical modeling were employed to investigate the Solute Suppressed Nucleation Zone (SSNZ) surrounding growing equiaxed grains in Al-13Cu alloys. Quantitative analysis of SSNZ and constitutional undercooling was conducted using image processing techniques. Solute concentration and SSNZ length in the <110> direction exceed those in the <100> direction, suggesting higher solute enrichment in dendrite centers. This causes greater undercooling in the dendrite growth direction (<100>) with faster dendrite growth rates. As equiaxed dendrites grow, SSNZ length in the <100> direction decreases while increasing significantly in the <110> direction. Utilizing data obtained from numerical simulations, we refined the analytical equation governing solute distribution preceding the solid–liquid interface under three-dimensional conditions, and the computational equation determining the SSNZ length. The SSNZ lengths derived from the optimized equation along the <100> and <110> directions demonstrate more agreement with both experimental observations and numerical simulation outcomes. Higher growth rates rapidly increase undercooling, limiting the development of nucleation-free zone. Additionally, SSNZ area growth slows at higher cooling rate, correlating with increased solute concentration and reduced area in SSNZ.

Stacking ensemble learning assisted design of Al-Nb-Ti-V-Zr lightweight high-entropy alloys with high hardness

To improve the accuracy and efficiency of machine learning models in predicting and designing the mechanical properties and designing of lightweight high-entropy alloys, we have trained multi-classification machine learning models using stacking ensemble method. This ensembled model achieves high prediction accuracy of 0.9457 and good anti-overfitting performance. Two candidate high-entropy alloys with high hardness from the predicted results (Al0.38Ti0.36V0.05Zr0.16Nb0.05 and Al0.51Ti0.28V0.04Zr0.16Nb0.01) were selected to prepare bulk samples using arc melting method. The experimentally measured micro Vickers hardness of two samples were 723.7 HV and 691.0 HV respectively, and only slightly lower than the hardness values predicted by the model, with an error of less than 8 %. The phase structure of the samples, which is a mixture of HCP and FCC, also agrees well with the predicted results. This indicates that our machine learning approaches is highly effective in predicting the hardness of high-entropy alloys, with accuracy that has been experimentally verified, thereby significantly enhancing the efficiency of designing new lightweight high-hardness high-entropy alloys.

Enhanced the mechanical properties and corrosion resistance of ultra-coarse grain WC-8Co cemented carbides by the introduction of Cu and Ni

This work investigated the microstructure and properties evolution of ultra-coarse grain WC-8Co cemented carbides with 0.8 wt% Cu and various Ni contents. The results showed that the simultaneous introduction of Cu and Ni could enhance the mechanical properties and corrosion resistance of ultra-coarse grain WC-8Co cemented carbide. After adding 0.8 wt% Cu and 0.8 wt% Ni, the hardness, strength and fracture toughness of WC-8Co alloy increased from 87.5 HRA, 1923 MPa and 17.05 MPa·m1/2 to 87.7 HRA, 2280 MPa and 19.47 MPa·m1/2, respectively. Moreover, the corrosion current densities of WC-6.4Co0.8Cu0.8Ni alloy were 12.59 μA·cm−2 in 0.1 M H2SO4 and 2.26 μA·cm−2 in 0.1 M NaOH, respectively, which were lower than those of WC-8Co alloy (23.24 μA·cm−2 and 2.34 μA·cm−2). In this regard, the introduction of Cu and Ni could save cobalt resources while improving the performance of ultra-coarse grain WC-8Co cemented carbides.

Mechanical and electrochemical characterization of CuAlNi alloys

The effect of copper composition on the structure and mechanical properties of CuxAlNi alloys was investigated using MD simulation and characterization methods. It was found that the structure of CuxAlNi alloys markedly resembles Cu composition, which alterations from the initial single (FCC) to (BCC) structure and then to a duplex BCC structure as the Cu content is raised. Nanoindentation measurements show that the hardness of CuAlNi alloys increases with Cu content. When there are more Al elements, the surface of the material is first combined with ions in seawater so that the corrosion potential is significantly reduced. This research seeks to identify CuAlNi alloys with improved properties through molecular dynamics simulations and experimental analyses, highlighting the connections between microstructure and mechanical behavior.

Sustainable development of agro bio-mass waste based AA6061-Tungsten carbide hybrid reinforced composites: A comprehensive performance investigation

The Recycling, Reusing, and Reduction (3R) strategy to solid waste management is proposed for exploiting the functionalities of wastes in enhancing base material performance, which could contribute to produce a sustainable product and environment. This study investigates the impact of organic and synthetic ceramic reinforcements; coconut shell ash (CSA), and tungsten carbide (WC) at various concentrations (1, 2, and 3 wt. % each) on microstructural and performance characteristics of sustainable AA6061 based hybrid composites. The composites are produced via the stir casting process with mechanized stirring. The microstructural characteristics of the produced aluminium hybrid composites (AMHC) are evaluated by FESEM/EDAX, FT-IR and XRD studies to examine their elemental composition, morphology and crystalline nature. The mechanical properties are investigated by charpy impact, tensile, compressive and micro-harness studies. The density and porosity analysis are employed to ascertain their physical characteristics. Morphology investigations show that the selected reinforcing materials are present and uniformly dispersed across the matrix's surface. The produced composite with 4 wt. % of CSA and WC reinforcements has the ability to improve the hardness (75.5 %), tensile strength (42.87 %), and compressive strength (55.71 %) of the base Aluminium alloy. Overall, using organic and synthetic ceramic substances as reinforcements for AA6061 alloy can result in sustainable high-performance composites for structural engineering applications across fields.

Effects of cerium micro-alloying on microstructural evolution and dispersion strengthening in Al-Yb-Er-Zr alloy

This study investigates the impact of trace cerium (Ce) addition on the precipitation behavior of Al-0.03Yb-0.03Er-0.06Zr (at%) alloys, with a focus on the formation of eutectic phases and nanoscale dispersoids. Ce, known for its low solubility in Al, preferentially segregates at grain boundaries, leading to the formation of Ce-rich eutectic phases and significant grain refinement. Isochronal annealing experiments revealed a double-peak hardening pattern. The first peak, associated with Al3RE (RE= Yb, Er, Ce) precipitates, demonstrated minimal sensitivity to Ce addition. The second peak, related to core-shell L12-Al3(RE, Zr) precipitates, exhibited a notable increase in hardness in the Ce-added alloy. Isothermal annealing at 450 °C and 475 °C further demonstrated that Ce accelerates the annealing-hardening response and increases the number density of Al3(RE, Zr) dispersoids at elevated temperatures. This enhancement may be attributed to Ce serving as an effective inoculant element and significantly reducing the stacking fault energy, which facilitates easier nucleation of these particles.

Enhancing aesthetics, hardness and corrosion resistance of aluminum alloy via deposition of Al/Si/AlN coatings

Enhancing aesthetics, hardness and corrosion resistance of aluminum alloy via deposition of Al/Si/AlN coatings

Research on tribological properties of new Ni-based single crystal alloy containing Re

Abstract The particles in high-temperature and high-speed airflow in the battlefield environment will form sliding friction and wear on the aeroengine turbine blades, thus reducing the service performance of the blades. However, few studies has been reported on the tribological properties of Ni-based single crystal alloy. Accordingly, the tribological properties of Ni-based single crystal alloys with different contents of Re (0 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, 4.5 wt% and 5.5 wt%) are investigated by tribological experiments and molecular dynamics simulations in this paper. The results of tribological experiments show that Ni-based single crystal alloy without Re exhibits the characteristics of abrasive wear and adhesive wear, while the wear state is significantly improved after adding Re element. In particular, the worn surface of Ni-based single crystal alloy containing 5.5% Re (NSCA5) is the smoothest and only a few minor defects are observed. In addition, the micro-tribological characteristics of Ni-based single crystal alloy are analyzed by molecular dynamics simulations, the results show that Re atoms can inhibit the dislocation movement and reduce the system potential energy, which enhance the stability and hardness of Ni-based single crystal alloy, thereby the wear resistance of the material are improved.

A lattice Boltzmann model with sharp interface tracking for the motion and growth of dendrites in non-equilibrium solidification of alloys

A lattice Boltzmann model (LBM) with sharp interface tracking is developed to simulate the motion and growth of dendrites in non-equilibrium solidification of alloys. The model is validated through comparative analysis with the drafting-kissing-tumbling (DKT) phenomena of two and three particles and the continuous growth model (CGM), and demonstrates its computational efficiency advantage without compromising accuracy by comparison with the multi-phase field (MPF) model. Subsequently, the model is utilized to investigate the dendrite morphology transition and primary dendritic arm spacing (PDAS). It is found that the velocity dependent solute partition and the resulting changes in constitutional undercooling strongly influence the estimated morphology region and PDAS. Moreover, the segregation and microstructure evolution during the rapid solidification were studied. And the results revealed that free dendrites lead to significant changes in microstructure and segregation under the influence of non-equilibrium effects. This work illustrates the great potential of the proposed model in simulating dendrites and microstructure evolution under a wide range of solidification conditions. Its suitability for extreme conditions and non-equilibrium solidification can contribute to the understanding of microstructure formation patterns and solute segregation in rapid solidification.

Wear analysis of teeth for roughing and finishing in the high-efficiency machining of hard alloys using carbide circular saw blades

Wear analysis of teeth for roughing and finishing in the high-efficiency machining of hard alloys using carbide circular saw blades

Dependence of Density, Hardness, Strength, and Dimensions of WC–15 Co Hard Alloy Samples on the Plasticizer Content in Workpieces Obtained Using a Plastic Mold Made by 3D Printing

Dependence of Density, Hardness, Strength, and Dimensions of WC–15 Co Hard Alloy Samples on the Plasticizer Content in Workpieces Obtained Using a Plastic Mold Made by 3D Printing

X-ray Diffraction Analysis and Micro Hardness of Ternary Alloy (Ti – 6Al – 4Nb)

This research aims to prepare the ternary alloy (Ti-6Al-4Nb) Using powder technology and studying X-ray diffraction analysis and micro hardness of this alloy. Titanium, aluminum, and niobium, powders were mixed together to homogenize the elements, and then the pressing process was carried out under pressure (5Ton) and for a period of time(60sec) For the purpose of obtaining a cohesive alloy in the form of discs, then the heat Treatment process (annealing) was conducted at different temperatures. (650,750,850,950,1050)˚C for two hours, the structural properties were studied through X-ray diffraction examination (XRD)And studying the mechanical properties by measuring the micro hardness using the Vickers hardness method before and after annealing, the results of the tests showed (XRD)The phases of the basic materials that make up the alloy, as the crystalline structure of titanium appeared to be of the hexagonal stacked type(HCP)As for aluminum, it appeared in a cubic system with concentric faces(FCC) and niobium in a body-centered cubic system (BCC)A new phase also appeared after the annealing process, which is the phase(AlNbTi2)Has a right rhombic crystal structure(Orthorhombic)The results of the micro hardness test (Vickers) showed that the annealing process has a positive effect on improving the mechanical properties, as the hardness value increases when temperatures increase.

In-situ study on the effect of Li concentration on hydrogen microporosity evolution in Al-Li alloys by synchrotron X-ray radiography

The nucleation and growth of hydrogen microporosity during the solidification of Al-Li alloys were in situ observed by synchrotron radiation X-ray radiography, and the effect of initial Li concentration on its evolution kinetics was investigated. The results show that the high Li concentration effectively contributes to the high-temperature nucleation effect of hydrogen microporosity during the solidification of Al-Li alloys, and significantly increases the nucleation and growth rates of hydrogen microporosity. When the initial Li concentration was 2.0 wt%, the nucleation supersaturation of hydrogen microporosity was 1.96, which was 3.5 times higher than that at low Li concentration (1.5 wt%), and the growth rate was up to 2.61 μm/s. In addition, the quantitative results of the final size, morphology, and distribution of the hydrogen microporosity based on 3D X-ray computed tomography (X-CT) showed that high Li concentration not only increased the volume of monolithic hydrogen microporosity, and increased the total number of microporosities, but also increased the degree of irregularity of hydrogen microporosity. The in-situ observation results can provide a new dataset for the establishment and validation of the hydrogen microporosity model of Al-Li alloys.

Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.

Enhancing the corrosion properties and microhardness of titanium alloy by laser surface remelting

Laser surface remelting (LSR) was performed on the Ti80 alloy, and the effects of different laser powers with 50 W, 100 W and 200 W on the microstructure, microhardness and corrosion properties were systematically investigated. The results showed that after LSR treatment, the microstructure of the Ti80 alloy was significantly refined because of the rapid cooling effect of laser processing, and the microhardness of the remelted zone gradually increased with the increase of laser power. The electrochemical test results reveal that the corrosion resistance of the Ti80 alloy can be significantly improved after LSR treatment and the corrosion resistance in 3.5 wt% NaCl solution was as follows from high to low: 100 W>50 W>200 W>As-received. It was concluded that the content of Ti2O3 decreased and TiO2 increased after LSR, and the stability of the passive film exhibited a corresponding improvement. The LSR can improve the surface hardness and corrosion resistance of the Ti80 alloy, which can be attributed to the homogenization of the composition of the remelting zone and the reduction of the point defect density of passive film. It is believed that results documented in this study can provide an important reference for deepening understanding of the surface modification mechanisms of LSRed Ti80 alloys.

A Study on the Hardness and Wear Properties of Surface-Coated Al Alloy

A Study on the Hardness and Wear Properties of Surface-Coated Al Alloy

Структура та властивості багатошарового металу, наплавленого електродними порошковими дротами з осердям із порошків феросплавів та гранульованих твердосплавних матеріалів

Comparative studies of the possibility of using granulated hard alloy powders as a charge of flux-cored wires for electric arc surfacing have been carried out. In the studies, granulated powder of the PG-R6M5 brand with a fraction of 50...300 μm was used. As a standard, a flux-cored wire was used, in the core of which there was a composition of powders of different ferroalloys of the same fraction. The content of the charge components in the core of the standard wire was selected and calculated so as to obtain a similar chemical composition to the wire containing granulated hard alloy powder. The test samples were obtained by layer-by-layer electric arc surfacing under the flux layer with flux-cored wires on low-carbon steel plates. To obtain identical dependences, the flux-cored wires had the same diameter and filling factor and differed only in the content of the core. The test samples were deposited under the same conditions with strict adherence to the deposition regimes, which were monitored using a high-speed analog-to-digital converter. It was determined that the use of granulated hard alloy powder as a charge of flux-cored wire has a positive effect on the melting characteristics of the wire and the stability of the welding process in general in comparison with the standard reference wire, the charge of which contains ferroalloys. This effect can be explained by the greater chemical purity of the granulated powder and the uniformity of the physicochemical properties of its particles in comparison with the powders of various ferroalloys. The determined features of the melting of the wire with a charge with granulated hard alloy powder have a positive effect on the quality of the formation of the multilayer deposited metal and its structure, leading to an increase in its homogeneity, some grinding of the grain and a decrease in the number and size of microdefects, which should positively affect the operational properties of the deposited metal. Keywords: electric arc surfacing, multilayer deposited metal, tool steels, granular hard alloy powder, ferroalloy, metal structure.

Microstructure, crystallographic texture and mechanical properties of the Zn–1%Mg–1%Fe alloy subjected to severe plastic deformation

The paper covers the production, analysis of the microstructure, crystallographic texture and deformation mechanisms of the ultrafine-grained (UFG) Zn–1%Mg–1%Fe zinc alloy demonstrating unique physical and mechanical properties compared to its coarse-crystalline analogs. The zinc alloy with improved mechanical properties was developed in two stages. At the first stage, based on the analysis of literature data, an alloy with the following chemical composition was cast: Zn–1%Mg–1%Fe. Then, the alloy was subjected to high-pressure torsion (HPT) to improve mechanical properties due to grain structure refinement and implementation of dynamic strain aging. The conducted mechanical tensile tests of the samples and assessment of the alloy hardness showed that HPT treatment leads to an increase in its tensile strength to 415MPa, an increase in hardness to 144HV, and an increase in ductility to 82%. The obtained mechanical characteristics demonstrate the suitability of using the developed alloy in medicine as some implants (stents) requiring high applied loads. To explain the reasons for the improvement of the mechanical properties of this alloy, the authors carried out comprehensive tests using microscopy and X-ray diffraction analysis. The microstructure analysis showed that during the formation of the ultrafine-grained structure, a phase transition is implemented according to the following scheme: Zneutectic + Mg2Zn11eutectic + FeZn13 → Znphase + Mg2Zn11phase + MgZn2particles + Znparticles. It was found that as a result of high pressure torsion in the main phases (Zn, Mg2Zn11), the grain structure is refined, the density of introduced defects increases, and a developed crystallographic texture consisting of basic, pyramidal, prismatic, and twin texture components is formed. The study showed that the resistance of pyramidal, prismatic and twin texture components at the initial stages of high-pressure torsion determines the level and anisotropy of the strength properties of this alloy. The relationship between the discovered structural features of the produced alloy and its unique mechanical properties is discussed.