Phase Composition Of Alloys Research Articles

Phase Composition, Microstructure and Mechanical Properties of Zr57Cu15Ni10Nb5 Alloy Obtained by Selective Laser Melting

Zr57Cu15Ni10Nb5 (more known as Vit-106) is a promising zirconium-based alloy with a high glass-forming ability, and belongs to the so-called bulk metallic glasses (BMG). Workpieces with a size of around one centimeter in all three dimensions can be obtained from a BMG alloy by casting. However, further increasing the cast size decreases the cooling rate and thus induces crystallization. Selective laser melting (SLM) is a well-known technique to overcome size limitations for BMGs because a workpiece is built by the addition of multiple melt portions in which the cooling rate is kept above the critical one. Currently, BMG parts obtained by SLM suffer from partial crystallization. The present work studies the influence of SLM process parameters on the partial crystallization of Vit-106 by metallography and the influence of the microstructure on mechanical properties by microhardness and wear resistance testing. Submicron crystalline inclusions are observed in an amorphous matrix of a Vit-106 alloy obtained by SLM. The size and the concentration of the inclusions can be controlled by varying the laser scanning speed. It is shown that submicron crystalline inclusions formed in the amorphous matrix during SLM can favorably affect microhardness and wear resistance.

Hydrogenation and the Formation of the Structure and Phase Composition of a VTI-4 Intermetallic Titanium Alloy after Hydrogen Alloying

Hydrogenation and the Formation of the Structure and Phase Composition of a VTI-4 Intermetallic Titanium Alloy after Hydrogen Alloying

The Effect of Changes in the Aging Temperature Combined with Deep Cryogenic Treatment on the Structure, Phase Composition, and Micromechanical Properties of the WE43 Magnesium Alloy

This paper examines the optimal aging temperature of WE43 alloy that has undergone precipitation hardening in conjunction with deep cryogenic treatment. The microstructure and phase composition were investigated, a microanalysis of the chemical composition was performed, and instrumental indentation tests were performed to determine the parameters of the micro-mechanical properties of the alloy after different heat treatment variants. It has been proven that a decrease in the aging temperature from 250 °C to 225 °C and the introduction of a deep cryogenic treatment lead to favorable changes in the microstructure of the alloy (reduction in grain size, increase in the number, and change in the type of β-phase precipitates). The changes in the alloy structure achieved by lowering the aging temperature contribute to the improvement of the micromechanical properties of the test material. The most advantageous results were recorded for an alloy subjected to solution treatment and aged at 225 °C for 24 h with deep cryogenic treatment: a 30% increase in hardness, a 10% increase in Young’s modulus, an improvement in elastic properties, and increased resistance to deformation of the alloy were shown compared to the initial (as-received) state. Raising the aging temperature to 250 °C leads to a phenomenon known as alloy overaging for both alloys after classical precipitation hardening and after deep cryogenic treatment. The results indicate the significant effectiveness of the proposed heat treatment in improving the service life of the Mg-Y-Nd-Zr (WE43) alloy.

Influence of the Phase Composition of Titanium Alloys on Cell Adhesion and Surface Colonization.

The pivotal role of metal implants within the host's body following reconstructive surgery hinges primarily on the initial phase of the process: the adhesion of host cells to the implant's surface and the subsequent colonization by these cells. Notably, titanium alloys represent a significant class of materials used for crafting metal implants. This study, however, marks the first investigation into how the phase composition of titanium alloys, encompassing the volume fractions of the α, β, and ω phases, influences cell adhesion to the implant's surface. Moreover, the research delves into the examination of induced hemolysis and cytotoxicity. To manipulate the phase composition of titanium alloys, various parameters were altered, including the chemical composition of titanium alloys with iron and niobium, annealing temperature, and high-pressure torsion parameters. By systematically adjusting these experimental parameters, we were able to discern the distinct impact of phase composition. As a result, the study unveiled that the colonization of the surfaces of the examined Ti-Nb and Ti-Fe alloys by human multipotent mesenchymal stromal cells exhibits an upward trend with the increasing proportion of the ω phase, concurrently accompanied by a decrease in the α and β phases. These findings signify a new avenue for advancing Ti-based alloys for both permanent implants and temporary fixtures, capitalizing on the ability to regulate the volume fractions of the α, β, and ω phases. Furthermore, the promising characteristics of the ω phase suggest the potential emergence of a third generation of biocompatible Ti alloys, the ω-based materials, following the first-generation α-Ti alloys and second-generation β alloys.

Cooperative regulation of mechanical properties and magnetoresistance effect in high-entropy alloys by spinodal decomposition

Adjusting the phase composition of high-entropy alloys is an effective approach to change its mechanical and magnetic properties. In this study, FeCoNiCr high-entropy alloys with Al addition (AlxFeCoNiCr; x = 0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.75) were prepared by argon arc melting to obtain a special spinodal decomposition structure. There precipitated body-centered cubic (BCC) phase in the face-centered cubic (FCC) phase matrix for the samples with Al (x = 0.25, 0.5, 0.75) addition. Furthermore, the increase in the Al content (x = 1.0, 1.25, 1.75) transformed the alloy into a BCC phase, and resulted in a spinodal decomposition in the alloy. This spinodal decomposition created a low-misfit coherent nanostructure combining the enriching AlNiCo ordered B2 matrix with enriching Fe–Cr BCC disordered nanoprecipitates. The difference in the distribution of chemical elements of the two phases leads to different magnetic properties and induces the magnetoresistance (MR) effect. This provides a pathway for the design of advanced functional high-entropy alloys.

Evolution of the Structure and Phase Composition of a High-Entropic CoCrFeNiCu Alloy during Prolong Annealing

Abstract—The thermal stability of a high-entropy alloy (HEA) CoCrFeNiCu was studied during long-term annealing for 204 days in the temperature range 873–1273 K. The alloy obtained by mechanochemical alloying of metal powders in a planetary mill during 120 min in an Ar environment is a substitutional solid solution based on a high-entropy phase with a face-centered cubic structure (FCC). Upon annealing, the initial FCC phase decomposes within 1–3 days into a copper-enriched FCC1 phase and a copper-depleted FCC2 phase with similar crystal lattice parameters of 3.60 and 3.57 Å, respectively. During the entire annealing time, the intensities of the diffraction lines of theFCC1 and FCC2 phases are redistributed, the dynamics and nature of which depends on the temperature and duration of the process. After the first three days and until the end of the annealing, the HEA retains the FCC structure of the substitutional solid solution, and the unit cell parameters of the formed FCC phases remain constant with an error of 0.1% up to 204 days. The five-component matrix formed after annealing has the chemical composition Co0.23Cr0.23Fe0.23Ni0.23Cu0.08 and is stable. Also, during the entire period of annealing, an increase in the grain size is observed: at first, when an active rearrangement of the structure occurs, the size increases rapidly, then, in the period from 1 to 30 days, grain growth is limited by the diffusion of components, and at very long time intervals, grain growth is even more inhibited.

Effect of Additional Hydrogen Alloying on the Phase Composition, Structure, and Deformability of Intermetallic Titanium Alloys with Orthorhombic Phase

Effect of Additional Hydrogen Alloying on the Phase Composition, Structure, and Deformability of Intermetallic Titanium Alloys with Orthorhombic Phase

Evolution of the Structure and Phase Composition of High-Entropy CoCrFeNiCu Alloy during Prolonged Annealing

Evolution of the Structure and Phase Composition of High-Entropy CoCrFeNiCu Alloy during Prolonged Annealing

Influence of atomic size effect on the properties of high entropy alloy coatings

In this study, laser cladding was used to prepare four high-entropy alloy coatings (HEACs) with different hardness on the titanium alloy substrate. Their hardness is based on the lattice distortion parameter (dimensionless parameter ε) for selection. Nominal composition of the four coatings designed basing on gradient lattice distortion parameters is CoCr0.5Fe2NiTi0.25 (ε = 4.64), CrMnMoTiV (ε = 6.10), CrFeMnMoTi (ε = 7.32), and CrMoNbTiZr (ε = 10.72). The phase composition of alloy coating systems is mainly fcc or bcc disordered solid solution accompanied by intermetallic compounds. The hardness of four coatings highly accord with the rule of “Hardness∝ε”, and theirs show the abrasive wear mechanism. As hardness of the coating increases, the coefficient of friction and wear loss decrease. Moreover, erosion resistance performance also shows similar results as friction test. In general, the method designing the hardness of high entropy alloy coatings is proven to be feasible herein. It provides favorable guidance for the development of the HEACs system with required hardness.

Effect of Heat Treatment on Two-Phase Ti – 22Al – 25Nb Alloy Phase Composition and Microhardness

Effect of Heat Treatment on Two-Phase Ti – 22Al – 25Nb Alloy Phase Composition and Microhardness

Phase Composition, Microstructure, Surface Hardness, and Corrosion Resistance of Surface Plasma Gas Nitrided Titanium Alloy Ti-10V-2Fe-3Al with Indirect Plasmatron

This study investigates and analyzes the influence of plasma gas nitriding with indirect plasmatron on the phase transformations, microstructure, surface microhardness, and corrosion resistance of titanium alloy Ti-10V-2Fe-3Al. In order to achieve this, the limits of the power used in this process are a minimum of 12 kW and a maximum of 35 kW. The thermochemical treatment time intervals are set at 5, 10, and 15 min. It is found that the phase composition of the surface layer after plasma gas nitriding consists of α-Ti, (N, O), TiN, and TiO2. Titanium oxides are detected only on the outermost surface of the nitrided layers. The measured hardness of the plasma gas nitrided layers obtained of Ti-10V-2Fe-3Al is up to 650 HK0.05. Potentiodynamic polarization analysis indicates that the subjects nitrided using 18 kW of power for 15 min have the lowest corrosion rate, while the highest corrosion rate is observed in those nitrided at 25 kW for 15 min.

Structure Evolution and Mechanical Properties of Sheet Al–2Cu–1.5Mn–1Mg–1Zn (wt.%) Alloy Designed for Al20Cu2Mn3 Disperoids

This work was focused on studying the possibility of increasing the strength of non-heat-treatable sheet alloy Al2Cu1.5Mn (wt.%) by the joint addition of 1% Mg and 1% Zn. The effect of these elements on the structure and mechanical properties of the new sheet Al2Cu1.5Mn alloy designed for Al20Cu2Mn3 dispersoids has been studied by calculations and experimental methods. The obtained data on the phase composition, microstructure, and physical and mechanical properties of the new alloy for different processing routes (including hot rolling, cold rolling, and annealing) have been compared with those for the ternary Mg- and Zn-free alloy. It has been shown that the formation of nanosized Al20Cu2Mn3 dispersoids (~7 vol.%) provides for the preservation of the non-recrystallized grain structure after annealing at up to 400 °C (3 h), while Mg and Zn have a positive effect on the strength due to the formation of alloyed aluminum solid solution. As a result, cold-rolled sheets of the Al2Cu1.5Mn1Mg1Zn model alloy showed a substantially higher strength performance after annealing at 400 °C in comparison with the ternary reference alloy. In particular, the UTS is ~360 vs. ~300 MPa, and the YS is 280 vs. 230 MPa. For the example of the Al2Cu1.5Mn1Mg1Zn model alloy, it has been shown that the system is promising for designing new heat-resistant alloys as a sustainable alternative to the 2xxx alloys. The new alloy has an advantage over the commercial alloys (particularly, 2219, 2024, 2014), not only in manufacturability but also in thermal stability. The sheet production cycle for the model alloy is much shorter because the stages of homogenization, solution treatment, and water quenching are excluded.

Microstructural evolution and mechanical properties of novel nanoparticles strengthened CoCrFeNi based high entropy alloy

A novel nanoparticles-strengthened CoCrFeNi(CuTi)x alloys (x = 0.2–1.0 at.%) were designed and synthesized to study the influence of CuTi concentrations on the microstructural evolution, phase composition and mechanical behavior of high-entropy alloys (HEAs) fabricated by Mechanical Alloying (MA) and Spark Plasma Sintering (SPS). The microstructure of the (CuTi)0.2 alloy is composed of CoCrFeNi-rich grey matrix, CrFe rich flap-like structure and Cu rich phases. With increasing CuTi content, the crystal structure changes from FCC to FCC + laves+η phases because of the formation of novel nanoparticles. A large amount of CoTi rich spherical particles and NiTi rich needle-like phases are observed in the (CuTi)0.6 alloy. The alloy with a density of 99.19% after SPS exhibits excellent comprehensive properties. Compared to single-phase FCC CoCrFeNi alloy, the compressive fracture strength increases from 871 MPa to 2083 MPa (∼139%). The solid solution strengthening of the FCC matrix and the formation of the secondary phases (Laves and η phases) are the main factors involved in improving the strengthening of the alloy. Most importantly, the Vickers hardness of the (CuTi)1.0 alloy is probably 1.7 times higher than that of the (CuTi)0.2 alloy.

Структура, фазовий склад і властивості сплаву АК12М2МгН з підвищенням вмістом заліза, обробленого в рідкому стані електричним струмом

The possibility of replacing the piston eutectic alloy of the Al-Si-Cu system AK12M2MgN, which was produced at OJSC "Zaporizhsky Aluminum Combine" from primary aluminum, with AK12M2MgNZH with an increased iron content, which will allow expanding the raw material base of production due to the use of scrap and waste. It is proposed to solve this problem by introducing into the technological process of processing the melt with a unipolar pulsed electric current during pouring according to specially developed modes. To investigate this possibility, experiments were conducted on the effect of electric current on the microstructure, phase composition of AK12M2MgN and AK12M2MgNZH alloys and their mechanical properties at temperatures of 20 oC and 300 oC. The melt was treated with an electric current in the following modes: electric current density (j) 100 - 400 A/cm2, pulse frequency (ν) 50 - 2000 Hz. The phase composition of alloys is considered. It is shown that the main iron-containing phase of the AK12M2MgN alloy is (Fe,Mn)3Si2AI15 (α) in the form of branched eutectic crystals. The acicular β-FeSiAI5 phase is practically absent. Unlike AK12M2MgN, the composition of AK12M2MgNZH alloy includes β-FeSiAl5 intermetallic and primary coarse crystals of (Fe,Mn)3Si2AI15 phase. After treatment of alloys in the liquid state with pulsed electric current in different modes, their microstructure and phase composition change significantly. The degree of differentiation of eutectic components increases. In particular, the linear size of eutectic silicon crystals, depending on the density and frequency of the electric current, decreases by 2-3 times. Primary crystals of the intermetallic (Fe,Mn)3Si2Al15 are formed in the AK12M2MgN alloy, which in cross-section have the appearance of compact, close to globular crystals. X-ray spectral studies have shown that despite the same crystallographic structure, eutectic and primary crystals of the (Fe,Mn)3Si2Al15 phase differ in the higher concentration of iron, manganese, copper and nickel in the latter. In the composition of the AK12M2MgNZH alloy, there is practically no acicular intermetallic β-FeSiAl5, the formation of which is one of the main reasons for the decrease in mechanical properties. Similar to the AK12M2MgN alloy, compact crystals of the primary phase (Fe,Mn)3Si2Al15 and a significant amount of the π-FeMg3Si6Al8 phase appear. Such structural changes ensured an increase in the mechanical properties at 20 and 300 oC of both the AK12M2MgN alloy and AK12M2MgNZH. The highest properties of both alloys are achieved at j = 100 A/cm2; ν = 1000 ‒ 2000 Hz. The characteristics of mechanical properties increase from 25 % to 40 %. The structural and phase changes caused by the processing of the AK12M2MgNZH melt with an electric current according to experimentally established modes provide it with mechanical properties at the level of the AK12M2MgN alloy with several higher heat resistance indicators. In addition, treatment of the melt with electric current allows to reduce the consumption of sodium-potassium fluxes by 15-50%; time of heat treatment for T1 from 10-12 hours. up to 2-3 hours.

Structure and Phase Composition of WNb Alloy Formed by the Impact of Compression Plasma Flows.

The results of a tungsten-niobium alloy synthesis by the impact of pulsed compression plasma flows are presented. Tungsten plates with a 2 μm thin niobium coating were treated with dense compression plasma flows generated by a quasi-stationary plasma accelerator. The plasma flow with an absorbed energy density of 35-70 J/cm2 and pulse duration of 100 μs melted the niobium coating and a part of the tungsten substrate, which caused liquid-phase mixing and WNb alloy synthesis. Simulation of the temperature distribution in the top layer of the tungsten after the plasma treatment proved the formation of the melted state. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the structure and phase composition. The thickness of the WNb alloy was 10-20 μm and a W(Nb) bcc solid solution was found.

From crack-prone to crack-free: Eliminating cracks in additively manufactured Ti-48Al-2Cr-2Nb alloy by adjusting phase composition

At present, it remains a challenge to additively manufacture Ti-48Al-2Cr-2Nb (TiAl4822) alloy by laser powder bed fusion (LPBF) technology because of the severe cracking in the building process. In this work, it was found that cracks in LPBFed TiAl4822 alloy were more likely to occur in the region near the interfaces between α2 and B2 phases, and the underlying mechanism was addressed. This leads to a strategy to reduce or eliminate these cracks via reducing the phase interfaces between α2 and B2 phases by adjusting its phase composition. Through the design of LPBF process parameters, the purpose of adjusting phase composition of LPBFed TiAl4822 alloy in a wide range (from nearly α2 single-phase, to α2 + B2 + γ, and then to nearly B2 single-phase) was realized. As expected, with the reduction of the interfaces between α2 and B2 phases, the cracking behavior has been significantly alleviated. The exciting result was that the crack-free sample could be achieved in the LPBFed TiAl4822 alloy with nearly α2 single-phase structure. Its compressive strength was measured to be 1460.7 MPa comparable to that of its casting counterpart. The present work makes it possible to additively manufacture crack-free TiAl4822 alloy by tuning phase composition.

Relative strength of β phase stabilization by transition metals in titanium alloys: The Mo equivalent from a first principles study

During the past decades, the use of Mo equivalent calculation has become a common method on titanium alloy designing due to the convenient and relatively accurate prediction of alloy phase composition as well as some mechanical properties. However, due to experimental limitation and difficulties, the current Mo equivalent empirical equation only includes a few transition elements with limited explanation for their effects on phase stability. In order to further study the role of all transition metals in stabilizing the titanium β phase and uncover the underlying mechanism, the relative strength of β phase stabilization by transition metals were calculated via the density functional theory in this study. The strength of β phase stabilizers was quantified based on the energy difference between the transition metal doped β phase titanium and ω phase titanium, which providing an excellent explanation for the classical Mo equivalent empirical equation obtained from the experimental measurement. The study found that d6 transition metal, such as Fe, have the strongest effect on β phase stabilization and the results provide a solid guideline for developing of new titanium alloys in the future.

The Effect of Boron Addition on the Structure and Mechanical Properties of Cu–Al–Ni–B Alloys with a Thermoelastic Martensitic Transformation

For the first time, data on the peculiarities of the structure of the Cu–Al–Ni–(B) alloys differing in the contents of alloying elements, namely, containing 10–14 wt % aluminum, 3, 4, 4.5 wt % nickel, and 0.02–0.3 wt % boron were obtained using optical, scanning, and transmission microscopy and X-ray diffraction analysis along with measurements of tensile mechanical properties. The effect of boron on the grain size, structure, phase composition, and mechanical properties of the shape-memory alloys has been studied. The localization of aluminum boride precipitates in the structure has been studied, and the effect of grain growthretardation in (α + β) and β Cu–Al–Ni–B alloys in both cast and heat-treated states has been found.

Description of the New Eutectic Al-Ca-Cu System in the Aluminum Corner

The structure of the new ternary eutectic Al-Ca-Cu system considered as a replacement for the ternary eutectic system Al-Ce-Cu widely used for additive manufacturing has been studied using experimental techniques. The liquidus projection of the Al-Ca-Cu system in the aluminum corner has been suggested based on experiential studies of the microstructure and phase composition of model alloys. The suggested structure of the diagram has two quasi-binary sections: (Al)-Al27Ca3Cu7 and (Al)-Al8CaCu4 and three invariant eutectic transformations: L→(Al) + (Al,Cu)4Ca + Al27Ca3Cu7 (at 5.6 wt.% Ca, 4.5 wt.% Cu, 595 °C), L→(Al) + Al27Ca3Cu7 + Al8CaCu4 (at 2.2 wt.% Ca, 13.5 wt.% Cu, 594 °C) and L→(Al) + Al8CaCu4 + Al2Cu (at 0.5 wt.% Ca, 34 wt.% Cu, 544 °C). The limit solubility of copper in aluminum solid solution (Al) at 530 °C reaches ~5.1 wt.% in the ternary phase field (Al) + Al8CaCu4 + Al2Cu and drops to ~2.4 wt.% in the (Al) + Al8CaCu4 + Al27Ca3Cu7 ternary phase field. For the example of the model ternary hypoeutectic alloys with a predominant content of the eutectic (Al,Cu)4Ca phase, it has been shown that the system is promising for designing new eutectic-type alloys with a natural composite structure.

OVERVIEW OF THE HIGH-ENTROPY ALLOYS CONCEPT

The article presents a review of the results of research on high-entropy alloys, describing the principles of their formation, the basic concepts and properties of high-entropy alloys. The existing categories of the entropic alloys are listed. The effects resulting from the formation of high-entropy alloys are described: high entropy, lattice distortion, sluggish diffusion and cocktail effects. It is noted that the traditional thermodynamic representations for multicomponent alloys require additions. It is also noted that the application of Hume-Rothery rules to predict the phase composition of high-entropy alloys shows some difficulties, since it is difficult to select a large number of elements having the same type of lattice and valence. The results of the analysis of a number of parameters and conditions which, according to the researchers' opinion, affect the structural state created by high-entropy alloys, taking into account which could allow to correctly predict the formation of structures in high-entropy. Analysis of the literature data has shown that at present there is no universal parameter that could allow the correct prediction of the formation of structures in multicomponent alloys systems. Methods for the preparation of powders of high entropy alloys are presented. The results of frequently used methods of obtaining coatings on the basis of high-entropy alloys, such as laser cladding, magnetron sputtering, electrochemical deposition and thermal spraying are reviewed. Disadvantages of obtaining coatings methods are described.