Ternary Eutectic Alloy Research Articles

Improvement of the strength of ternary eutectic V-Si-B alloys at ambient and high temperatures due to Cr additions

In the present study high-temperature compression tests on a chromium-alloyed ternary eutectic V-9Si-6.5B are reported. The ternary eutectic composition is located within the VSS (V solid-solution)-V3Si-V5SiB2 three-phase region of the respective V-rich corner of the phase diagram. The high-temperature compressive yield stresses were determined by the 0.5 % offset method and the plastic strain was obtained by subtracting the combined compliance of the testing machine and the specimen from the individually measured load-displacement curves. The microstructures in the as-cast and heat-treatment state (1400 °C / 100 hrs) were analyzed using SEM, EBSD and TEM observations. The effect of Cr on the ternary eutectic formation was studied. After compression testing, dislocation activities were observed in the VSS and V3Si phases, while the ternary intermetallic phases were dislocation-free. The high-temperature plasticity in the Cr-added ternary eutectic alloys V-9Si-6.5B+xCr is mainly governed the VSS phase which forms the major phase of the eutectic. Thus, Cr additions are found to contribute to solid-solution strengthening in the ternary eutectic alloys while strongly influencing the deformability by decreasing the temperature at which brittle failure occurs in the present compression experiments.

Achieving enhanced strength retention at elevated temperatures in ultrafine-fibrous interconnected Al–Ce–Ni eutectic alloy solidified under super-gravity field

Super-gravity field was reported to strongly intensify the buoyancy-driven flow of liquid during solidification, affecting the solute convection and morphology of eutectic structure in binary alloys. In ternary eutectic alloys, certain two-phase regions with a coarse structure can usually be detected concurrently along with three-phase eutectics, leading to the formation of heterogeneous structure with limited ductility. Currently, Al–Ce–Ni ternary eutectic alloy was chosen as a modal system, which was reported for the first time to be solidified under super-gravity field with high volume fraction of three-phase eutectics. Meanwhile, the formation of ultrafine-fibrous interconnected Al11Ce3–Al3Ni eutectic clusters with more “chains” and higher spatial connectivity was detected mainly due to the relatively higher nucleation rate. The high volume fraction and refinement of interconnected Al11Ce3–Al3Ni eutectic clusters with excellent thermal stability could contribute to enhancement of ductility and tensile strength at elevated-temperature. Interestingly, the strength retention at 300 °C and 400 °C were able to reach up to ∼68.1 % and ∼33.2 %, respectively.

Ternary eutectic growth and associated tensile properties of directionally solidified Al87Si11Ni2 alloy

The directional growth mechanism and associated tensile properties of ternary Al87Si11Ni2 eutectic alloy were investigated within a wide growth velocity range from 1 to 120 μm s−1 at a constant temperature gradient of 380 K cm−1. If eutectic growth velocity was below 40 μm s−1, this alloy exhibited a ternary lamellar eutectic structure composed of Si plates, Al3Ni chips and αAl matrix. As growth velocity increased to faster regime, the microstructure evolved into a complex structure characterized by primary αAl dendrites plus ternary eutectics. Correspondingly, the preferred crystalline orientation along solidification direction transformed from 101αAl //010Al3Ni // 101Si to 001αAl // 010Al3Ni //113Si. The tensile strength initially increased with the rise of growth velocity until 40 μm s−1, primarily due to the refinement of eutectic structure, and then decreased beyond this threshold, mainly resulting from the coarsening of primary αAl phase.

Novel microencapsulated ternary eutectic alloy-based phase change material

Recent applications of phase change materials (PCMs) include energy storage, transportation, and management. Multicomponent PCMs represent a primary tool for regulating operating temperatures across a broad range to accommodate diverse requirements across various temperature ranges. Moreover, the microencapsulation of PCMs promotes their manageability and functionality. However, microencapsulated PCMs (MEPCMs) with ternary eutectic alloy systems are yet to be reported. Moreover, various technical challenges impede the integration of components during PCM fabrication. In this study, a core–shell-type MEPCM with a ternary eutectic Al–Cu–Si alloy system was successfully developed for the first time. The MEPCM was prepared over two simple steps: (1) the formation of a precursor shell on the PCM particles using boehmite treatment and (2) the heat oxidation treatment to form a stable oxide shell. The fabricated MEPCM exhibited a melting point of 517 °C and a latent heat of 353 J g−1. MEPCMs operating at this temperature have not previously been reported. Furthermore, the heat storage density of the fabricated MEPCM was significantly higher than that of other reported MEPCMs. Additionally, the fabricated MEPCM exhibited high durability under 100 cycles of heat storage and release tests, retaining >90 % of its latent heat capacity. Therefore, for the first time, this study successfully developed a core–shell-type MEPCM with a ternary eutectic system.

Directional Solidification of Al–Si–Ti Irregular Ternary Eutectic Alloy and Thermophysical Properties

Directional Solidification of Al–Si–Ti Irregular Ternary Eutectic Alloy and Thermophysical Properties

Promotion or Suppression of Eutectic and Peri-Eutectic Growth in Containerlessly Processed Fe–Ni–Ti Alloys

The competitive growth mechanisms of ternary eutectic and peri-eutectic transitions of liquid Fe–Ni–Ti alloys were investigated by drop tube technique. As liquid undercooling and cooling rate increased, the microstructure of eutectic Ni40.6Fe36.4Ti23 alloy transformed from the mixture of primary Ni3Ti phase and ternary eutectic into complete ternary eutectic. The predominant growth mode of independently grown Fe2Ti intermetallic phase varied from nonfaceted to faceted growth, while the γ-Fe(Ni) and Ni3Ti phases kept cooperative growth and formed a lamellar structure owing to the coherent interface along \((1 \overline{1}1)_{\gamma }\) and \((0001)_{{{\text{Ni}}_{{\text{3}}} {\text{Ti}}}} \). The peri-eutectic transformation in Fe66.5Ni17.6Ti15.9 alloy was suppressed due to the preferential growth of the primary α′-Fe phase as droplet size decreased. A needle-like Fe2Ti phase precipitated from the supersaturated α′-Fe phase during rapid solidification, and the α-Fe/Fe2Ti interface was characterized as semicoherent. The wear rate and friction coefficient of the ternary eutectic alloy firstly increased and then decreased as controlled by the combined factors of the microstructural transition and grain refinement. For the peri-eutectic alloy, the refinement of microstructure significantly improved the friction performance after rapid solidification. Moreover, the ternary eutectic alloy had a better wear resistance than peri-eutectic alloy, ascribed to the hardening intermetallic phases and the refined microstructure.

The effect of Sr additions on Al–Cu–Si ternary eutectic alloys for a high-ductility bimodal microstructure

Al–Cu–Si ternary eutectic alloys with a bimodal eutectic structure exhibit a good combination of strength and plasticity owing to the multiscale hierarchical microstructure. Previous studies have reported that bimodal eutectic structures can be successfully prepared by rapid solidification at a cooling rate of greater than 102 °C/s. In the present study, a bimodal eutectic structure was successfully prepared at a cooling rate of less than 10 °C/s by adding a small amount of Sr to Al–Cu–Si ternary eutectic alloys. Additions of Sr led to a notable modification of the microstructure from a mixed eutectic structure to a bimodal eutectic structure. Samples with the bimodal eutectic structure showed greater hardness, strength, and elongation than samples with mixed eutectic structure. In particular, the elongation increased significantly from 6% to 28%. The additions of Sr changed the microstructure of the Al–Si phase from needles to globular shapes, which are finely dispersed all through the microstructure. These results indicate that the improved mechanical properties with the addition of Sr can mainly be attributed to the development of a multiscale hierarchical microstructure with fine eutectic cells.

Role of interfacial energy and liquid diffusivities on pattern formation during thin-film three-phase eutectic growth

In this paper, we investigate three-phase eutectic growth during thin-film directional solidification of a model symmetric ternary eutectic alloy. In contrast to two-phase eutectics that have only a single possibility, ${\alpha}{\beta}{\alpha}{\beta}$..., as the growth pattern, during three-phase eutectic growth infinite possibilities exist. Here, we explore the possible existence of pattern selection influenced by the change in the solid-solid interfacial energies and the diffusivities. We begin the study by estimating the undercooling vs. spacing variation for the simplest possible configurations of pattern lengths 3 and 4, where phase-field simulations are utilized to quantify the influence of the solid-solid interfacial energy and the contrast in the component diffusivities. Subsequently, extended simulations consisting of multiple periods of ${\alpha}{\beta}{\delta}$... as well as ${\alpha}{\beta}{\delta}{\beta}$... are carried out for assessing the stability of the configurations to long-wavelength perturbations in spacing. Thereafter, growth competition among the simplest patterns is investigated through phase-field simulations of coupled growth of configurations of the type [${\alpha}{\beta}{\delta}]_m[{\alpha}{\beta}{\delta}{\beta}]_n$, (m,n) being the respective number of periods. Finally, pattern selection is studied by initializing with random initial configurations and classifying the emerging patterns based on the phase sequences. The principal finding is that, while there is no strong phase selection, between the solid-solid interfacial energies and the contrast in the component diffusivities, we find the latter to strongly influence pattern morphology.

Surface tension measurement of Nd − Fe − B − X melts (X = O, Cu, Ga, In) as simulated substances of Nd-rich phase in Nd magnet

The microstructure of a neodymium (Nd)- iron (Fe)- boron (B) sintered magnet must be appropriately controlled in the sintering and annealing processes to improve the performance of the Nd magnet. In this study, the surface tension of molten Nd alloys containing copper (Cu), gallium (Ga), or indium (In) as a simulated substance of the Nd-rich phase was measured to investigate the formation mechanism of the microstructure from the perspective of physicochemical properties of the Nd-rich phase. The surface tension of the molten Nd–Fe alloy at the liquidus gradually decreased with an increase in Nd concentration, accompanied by a decrease in temperature. This indicates that lower temperatures are advantageous for the wetting-infiltration of the liquid Nd-rich phase into the interspace between the Nd2Fe14B grains in the magnet. While considering the dependence of the surface tension of the Nd–Fe–B ternary eutectic on the oxygen (O) concentration, no significant difference in the surface tension was determined in the investigated range of O concentrations (600–3000 mass ppm O). The surface tension of the ternary eutectic alloy did not significantly change with the substitution by Cu, which implies that the change in surface characteristics due to the addition of Cu is not the primary reason for the improvement in wetting of the Nd-rich phase. The surface tension of the ternary eutectic alloy increased with the substitution by Ga, but decreased with the substitution by In.

Hot Tearing Behavior in Double Ternary Eutectic Alloy System: Mg-Ce-Al Alloys

The hot tearing behavior of the double ternary eutectic alloy system, Al-6Mg-xSi (0 to 6.0 wt pct Si) alloys, was evaluated by a constrained rod casting mold equipped with a thermocouple and a load cell connected to a data acquisition system. Experimental results were compared with the results calculated by Scheil’s model using Pandat software to predict the occurrence of hot tearing in Al-6Mg-xSi alloys. The curve of hot tearing susceptibility contained two peaks, which were mainly affected by the double ternary eutectic reactions and the solidification phases evolution. And it agreed with the Kou’s hot tearing index precisely. The types and fractions of solidification phases (Al3Mg2, Mg2Si, and eutectic Si) determined by the addition of Si content changed the freezing range and eutectic liquid fraction greatly. In addition, the types, fractions, sizes, and distributions of solidification phases affected the nucleation, propagation, and healing of hot tear cracks. The maximum contraction force value decreased as the reduction of volume shrinkage coefficient due to the addition of Si content. The drop-in force value on the contraction force curve could indicate the occurrence of hot tearing, and predict the hot tearing susceptibility when considering the shrinkage coefficient.

Elevated temperature tensile properties of a ternary eutectic Al–27%Cu–5%Si cast alloy

Eutectic alloys have several advantages when compared to single-phase systems. Moreover, the solidification characteristic and microstructural features of eutectic alloys have continued to gain more attention in recent years due to their impact on the properties and performance of such eutectic materials. In this study, a eutectic Al–27%Cu–5%Si ternary alloy was investigated to understand its microstructural formation and its influence on the hardness and high-temperature tensile properties of the alloy. The eutectic composite was produced through a rapid solidification technique and its microstructure characterized by an optical microscope as well as a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). The hardness of as-cast alloy was evaluated at room temperature while its tensile properties were investigated at temperatures ≤400 °C. The results revealed that the cast alloy consists of both binary and ternary eutectic microstructures with different length-scales, which has considerably contributed to the mechanical performance of the eutectic composite up to 300 °C when compared to the traditional Al–Si (A319) cast alloy. The alloy displays a high hardness value of 224HV and a relatively higher elevated-temperature tensile strength of 217 MPa at 300 °C. The tensile strengths of the ternary eutectic alloy are 54% and 139% higher than that of the reference A319 casting alloy at temperatures of 200 °C and 300 °C, respectively.

Effect of Temperature Gradient and Growth Velocity on Microstructure and Mechanical Properties on Zn–7Al–3Cu Ternary Eutectic Alloy

In the present work, microstructure and mechanical properties of Zn–7Al–3Cu (wt%) ternary alloy are investigated depending on the temperature gradient and growth velocity. The alloy was prepared in the designated composition in a vacuum melting and casting furnace and then filled into the graphite sample moulds. The samples were directional solidified with various temperature gradients (6.7–10.7 K/mm) at a constant growth velocity (16.4 μm/s) and with various growth velocities (8.3–166.0 μm/s) at a constant temperature gradient (10.7 K/mm) in a Bridgman-type furnace. Microstructural images of solidified samples were taken with light microscope and scanning electron microscope. Eutectic spacings were measured from these images. Microhardness, ultimate tensile strength, yield strength and modulus elasticity values of each sample produced at various solidification parameters were also measured. The effect of temperature gradient and growth velocity on the eutectic spacing, microhardness, ultimate tensile strength, yield strength and modulus elasticity was determined using linear regression analysis. While the microhardness, ultimate tensile strength, yield strength and modulus elasticity values increased with increasing temperature gradient and growth velocity values or decreasing eutectic spacing, the elongation values decreased. Fractographic results show that the type of fracture is brittle.

Design of Eutectic High Entropy Alloys in Al–Co–Cr–Fe–Ni System

In the present work, a simple approach is proposed for predicting the compositions of eutectic high entropy alloys (EHEAs) in Al-Co-Cr-Fe-Ni system. It is proposed that eutectic lines exist between certain eutectic alloys in this system and, as a result, new eutectic or near-eutectic compositions can be obtained by mixing the alloys which are located on the same eutectic line. The approach is applied for a series of experimentally verified eutectic alloys and new eutectic or near-eutectic alloys are designed for Al-Co-Cr-Fe-Ni system. Furthermore, by investigating the compositions of verified eutectic alloys in Al-Co-Cr-Fe-Ni system, compositional diagrams are proposed which show the relations between the concentrations of constituent elements in eutectic alloys. The compositional diagrams suggest that EHEAs are derived from binary and ternary eutectic alloys. Moreover, the proposed diagrams can be considered as convenient methods for evaluating the composition of EHEAs in Al-Co-Cr-Fe-Ni system.

Transient directional solidification of a eutectic Al–Si–Ni alloy: Macrostructure, microstructure, dendritic growth and hardness

The Al-11 wt%Si-5 wt%Ni eutectic alloy was directionally solidified (DS) under transient heat flow conditions at cooling rates in a range of about 1–25 °C/s along the length of the casting. For comparison purposes binary Al-11 wt%Si and Al-5 wt%Ni alloys were also solidified under similar experimental conditions. Initially characterized by columnar grains, the macrostructure of the ternary DS alloy casting evolved during solidification to a columnar to equiaxed transition (CET) at critical cooling rates of about 1.3–1.6 °C/s, i.e. more than 7 times higher than the CET critical value determined in the literature for Al–Ni and Al–Si alloys. The microstructure of the ternary alloy casting is shown to be constituted by primary Si crystals and α-Al dendritic branches surrounded by the eutectic phase (α-Al+Si+Al3Ni), with the Al3Ni phase having initially a plate-like morphology, which with the decrease in the solidification kinetics, evolved to a fishbone morphology. The pertinent scaling laws representing the dendritic growth of the eutectic ternary alloy, properly compared to those of the examined Al–Si and Al–Ni binary alloys are outlined. The scale of the dendritic α-Al phase is shown to affect the Vickers hardness (HV) along the length of the ternary eutectic alloy casting, and a Hall–Petch type equation is proposed relating HV to the secondary dendritic arm spacing.

Co-Cr-Mo-C-B metallic glasses with wide supercooled liquid region obtained by systematic adjustment of the metalloid ratio

We investigate the influence of the ratio between carbon and boron on glass-forming ability, thermal stability and mechanical properties of the Co65Cr13Mo22 ternary eutectic alloy modified by carbon and boron addition. Besides, the correlation between the extension of the supercooled liquid region (SCLR) and three bonding parameters, i.e. electronegativity, atomic size, and valence electron is investigated. The results reveal that carbon is more effective than boron to form a glassy phase in this system, and fully glassy alloys or metallic glass composites can be obtained when the metalloid contents are in the range of 20–25 at.%. Fully glassy alloys are only obtained when the carbon-to-boron ratio is 2:1. The glassy alloys and the glass composites exhibit high strength and extraordinarily wide SCLRs of >120 K. The width of the SCLR of the Co-based BMGs can be articulated as a function of three bonding parameters, which is different to the relationship previously observed for Fe-, Mg- and Pd-based BMGs. Based on these findings we propose the optimum C/B ratio for glass phase formation and the new criterion for predicting the width of the SCLR of Co-based BMGs by the three bonding parameters.

Microstructure characterization and hardness of Al-Cu-Mn eutectic alloy

The composition of Al-Cu-Mn ternary eutectic alloy was chosen to be Al-32.5wt.%Cu-0.6wt.%Mn to the Al2Cu and Al12CuMn2 solid phases within an aluminum matrix (α-Al) from its melt. The Al-32.5wt.%Cu-0.6wt.%Mn alloy was directionally solidified at a constant temperature gradient (G=8.1 K·mm-1) with different growth rates, 8.4 to 166.2 μm·s-1, by using a Bridgman-type furnace. The eutectic temperature (the melting point) of 547.85 °C for the Al-32.5wt.%Cu-0.6wt.%Mn alloy was obtained from the DTA curve of the temperature difference between the test sample and the inert reference sample versus temperature or time. The lamellar spacings (λ) were measured from transverse sections of the samples. The dependencies of lamellar spacings (λAl-Al2Cu) and microhardness on growth rates were obtained as, λAl-Al2Cu=3.02V-0.36, HV=153.2(V)0.035, HV=170.6(λ)-0.09 and HV=144.3+0.82(λAl-Al2Cu)-0.50, HV=149.9+53.48V0.25, respectively, for the Al-Cu-Mn eutectic alloy. The bulk growth rates were determined as λAl-Al2Cu2·V = 25.38 μm3·s-1 by using the measured values of λAl-Al2Cu and V. A comparison of present results was also made with the previous similar experimental results.

Antimicrobial properties of ternary eutectic aluminum alloys.

Several Escherichia coli deletion mutants of the Keio collection were selected for analysis to better understand which genes may play a key role in copper or silver homeostasis. Each of the selected E. coli mutants had a deletion of a single gene predicted to encode proteins for homologous recombination or contained functions directly linked to copper or silver transport or transformation. The survival of these strains on pure copper surfaces, stainless steel, and alloys of aluminum, copper and/or silver was investigated. When exposed to pure copper surfaces, E. coli ΔcueO was the most sensitive, whereas E. coli ΔcopA was the most resistant amongst the different strains tested. However, we observed a different trend in sensitivities in E. coli strains upon exposure to alloys of the system Al-Ag-Cu. While minor antimicrobial effects were detected after exposure of E. coli ΔcopA and E. coli ΔrecA to Al-Ag alloys, no effect was detected after exposure to Al-Cu alloys. The release of copper ions and cell-associated copper ion concentrations were determined for E. coli ΔcopA and the wild-type E. coli after exposure to pure copper surfaces. Altogether, compared to binary alloys, ternary eutectic alloys (Al-Ag-Cu) had the highest antimicrobial effect and thus, warrant further investigation.

Morphology and Phase Formation During the Solidification of Al-Cu-Si and Al-Ag-Cu Ternary Eutectic Systems

The microstructure of ternary alloys in the Al rich corner of the Al-Cu-Si and Al-Ag-Cu systems were analyzed in order to determine the solidification path in the different structural regions expected from the equilibrium phase diagram. The analysis was based on theoretical models developed in the literature for solidification of ternary eutectic system alloys under simple lever rule assumptions. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDAX) were used to study the microstructure formed in each case. The observations were consistent with model predictions: Al-Cu-Si system showed two binary eutectics: non faceted-non faceted (nf-nf) AlCu and faceted-non faceted (f-nf) AlSi, Al-Ag-Cu system showed 2 binary regular eutectics (nf-nf) and a ternary semi-regular Brick type eutectic. The results provided an example of a methodology for use in ternary and multicomponent alloys.

Study of pattern selection in 3D phase-field simulations during the directional solidification of ternary eutectic [formula omitted]-[formula omitted]-[formula omitted

During the directional solidification of ternary eutectic alloys, different arrangements of the three solid phases evolve, leading to multiple microstructure patterns. These patterns influence the macroscopic properties of the alloy. Different arrangements are even found in single micrographs for the same imposed process conditions. Gaining a better understanding of the complex mechanisms leading to these different patterns is crucial to obtain tailored microstructures with specific properties. To exploit the different patterns which appear in ternary eutectic Al-Ag-Cu, a coupled approach is undertaken using a large-scale simulation and extensive parameter studies on smaller 3D domains. Three patterns found in both large-scale simulations as well as experimental micrographs are investigated with smaller domain size simulations by systematically varying the lamellar spacings. The resulting undercooling-spacing correlations of all investigated phase arrangements follow a Jackson-Hunt-type shape. Different stability ranges of the initially set microstructure are found, and depending on the lamellar spacings, the pattern with the lowest undercooling changes. The combination of both outcomes gives an explanation for the presence of different patterns within single micrographs of directionally solidified ternary eutectic alloys.

Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification

Sn-36Bi-22Cu (wt.%) ternary eutectic alloy was prepared using vacuum melting furnace and casting furnace. The samples were directionally solidified upwards solidification rate varying from 8.3 to 166 µm/s and at a constant temperature gradient (4.2 K/mm) in a Bridgman-type directional solidification furnace. The composition analysis of the phases and the intermetallics (Cu3Sn and Cu6Sn5) were determined from EDX and XRD analysis respectively. The variation of the lamellar spacing (Bi-rich phase) and the Cu3Sn phase spacing with the solidification rate were investigated. The dependence of microhardness, ultimate compressive strength and compressive yield strength on solidification rate were determined. The spacing and microhardness were measured from both longitudinal and transverse sections of the samples. The dependence of microhardness on the lamellar spacing and the Cu3Sn phase spacing were also determined. The relationships between phase spacings, solidification rate and mechanical properties were determined from linear regression analysis.