B2 Phase Research Articles

The effect of different C contents on the microstructure evolution and mechanical properties of Ti45Al6Nb alloy

The content of C element and in-situ Ti2AlC phase is adjusted to reduce the content of B2 phase in the TiAl matrix, ultimately improving the compressive properties of TiAl alloys. Results show that there is a high content of B2 phase inside the lamellar colony, and the Nb content in the B2 phase is higher than that dissolved in matrix. The addition of C element results in the formation of a round rod like reinforcing phase and refining the lamellar colony. As the C content increases from 0 to 3.0 at. %, the content of in-situ Ti2AlC reinforcing phase increases from 0 to 17.8 vol. %, the content of B2 phase decreases from 10.4 to 1.4 vol. %, and the size of the lamellar colony decreases from 161.3 to 19.5 μm. The decrease in the content of B2 phase is due to the preferential formation of Ti2AlC reinforcing phase in the liquid, Nb will preferentially dissolve in it, resulting in a more uniform distribution of Nb in the solidified structure and reducing the segregation of Nb. Then, Ti2AlC particles act as heterogeneous nucleation, increasing the nucleation sites in the alloy melt and refining the microstructure. According to the results of the compression test, as the C content increases from 0 to 2.5 at. %, the compressive strength increases from 1186.9 to 2154.5 MPa, and the compressive strain increases from 6.5 to 20.2 %. Therefore, the precipitation strengthening effect of Ti2AlC, the grain boundary strengthening effect of refined microstructure, and the decrease in the content of B2 phase jointly contribute to the improvement of the compressive properties at room temperature.

Microstructure and properties of a shape memory alloy Ti–Ni–Al–V fabricated by double-wire arc additive manufacturing

In this study, a novel heterogeneous double-wire arc additive manufacturing method was used for the in-situ synthesis of a novel Ti–Ni–Al–V alloy wall. The results indicated that the synthesis wall was composed of the NiTi2, B2, and Ni4Ti3 phases from the bottom to the top. With an increase in deposition layers, the Ti2Ni content decreased. The hardness at the bottom was ∼685.4 HV0.2, while that of the middle and stable regions was 553 HV0.2. The maximum compressive strength was 2100 MPa. The fracture morphology was brittle. After cyclic compression, the recoverable and unrecoverable strains were 4.79 % and 1.21 %, respectively, indicating excellent recovery characteristics.

Examining the Effect of Drums Alive® Intervention on Verbal Communication and Task Engagement in Children with Autism Spectrum Disorder

Background: Children diagnosed with autism spectrum disorder (ASD) often encounter difficulties in verbal communication (VC) and task engagement (TE). This study aimed to investigate the impact of the Drums Alive® (DA) program, implemented as an antecedent-based intervention, on VC and TE among children with ASD. Methods: This study involved five male participants with ASD, aged four to six years. Employing an eight-week single-subject withdrawal research design (A1-B1-A2-B2), the research comprised structured activities (e.g., Legos, Jenga, hopscotch, and matching cards, etc.) in the A1 and A2 phases, each lasting 15 minutes. Subsequently, the B1 and B2 phases featured similar activities but integrated the DA intervention before the structure activities, lasting 30 minutes in total. Visual inspection was utilized to code and analyze the data. Results: During the B1 and B2 sessions, all five participants exhibited higher TE percentages compared to the A1 and A2 phases. However, no significant increase in VC percentages was observed. Conclusion: While the evidence is limited, the study suggests potential support for the effectiveness of the DA intervention in enhancing TE among children with ASD. Nevertheless, further research involving a larger sample size is imperative to validate the impact of the DA program comprehensively

Synergistic control of microstructures and properties in eutectic high-entropy alloys via directional solidification and strong magnetic field

The AlCoCrFeNi2.1 eutectic high-entropy alloy (Ni2.1 EHEA), as an exemplary representative of the high-entropy alloy family, has garnered significant research attention owing to its exceptional comprehensive properties. In this study, we investigated the influence of various growth velocities on the microstructure, lamellar spacing, and mechanical properties of the Ni2.1 EHEA. We observed that at lower growth velocities, the structure consisted of an alternating face-centered-cubic (FCC) phase and B2 phase lamellae aligned in a single direction, with the lamellae orientation parallel to the direction of the heat flow. The yield strength increased with the growth rate, while the ultimate tensile strength decreased with increasing the growth velocity. Ductility remained relatively consistent, and a double yield phenomenon was observed in the elastic-plastic deformation region. Under conditions of high growth velocities, the microstructure transitioned from a single-directional full lamellar structure to a multi-stage lamellar arrangement. The most favorable comprehensive mechanical properties were achieved at a growth rate of 200 μm/s, resulting in a yield strength of 450 MPa, an ultimate tensile strength of 1092 MPa, and a remarkable ductility of ∼32% in the directionally solidified samples—double that of the arc-melted sample. The evolution law of directional solidification structures under the coupling effect of different magnetic fields and different growth rates was studied. The interaction of the thermoelectric-magnetic force and thermoelectric-magnetic convection and the potential mechanism of microstructure evolution under the effect of magnetic field were deeply analyzed. The results reveal that at a growth rate of 2 μm/s, the spacing between eutectic layers decreases as the magnetic induction intensity increases, leading to the transformation of some regular layers into spherical layers. Similarly, at a growth velocity of 10 μm/s, the eutectic structure exhibited a Columnar-to-equiaxed transition (CET). However, as the growth rate further increases, the limited exposure time to the magnetic field prevented significant structural changes.

Effects of Al addition on the microstructure and mechanical properties of AlxCoCrFeNi2.1 high-entropy alloys

To investigate the effect of Al content on the microstructure evolution and properties of AlxCoCrFeNi2.1 high-entropy alloys, the AlxCoCrFeNi2.1 high-entropy alloys (=0.5, 0.8, 1.0, 1.2 and 1.5) were prepared by vacuum arc melting. The results show that all the designed alloys are composed of single face-centered cubic (FCC) and ordered body-centered cubic (B2) phases. With the increase of Al content, the volume fraction of FCC phase decreases while that of B2 phase increases. In addition, the increasing Al content leads to the sequential increase of the hardness and yield strength of the alloys, while both the plasticity and compressive strength decrease. And the corresponding wear rate decreases from 312.9 × 10−5 mm2 N−1 to 55.3 × 10−5 mm2 N−1. It is revealed that the wear mechanism transforms from initially dominant abrasive wear with adhesive wear as a supplement to the mechanism dominated by adhesive wear with abrasive wear as a supplement, and finally to the oxidation wear plus abrasive wear. The experimental results show that the Al1.2CoCrFeNi2.1 alloy has the most excellent comprehensive performance, with an average hardness of 441 HV, compression ratio of 36.4%, compressive strength of 2618 MPa and wear rate of 68.0 × 10−5 mm2 N−1.

Analysis of phase stability and chemical segregation in the Mo-V alloys using a generalized embedded atom method potential

A new interatomic potential for the Mo-V system is introduced to facilitate the study of phase stability and mechanical properties at lower temperatures. This potential is based on a generalization of the embedded atom method and includes contributions from embedding energy, explicit two- and three-body interactions and nonlocal many-body interaction terms. The parameters of the potential are optimized by using data from ab initio density functional theory (DFT) calculations. The potential is rigorously validated across a range of physical properties, such as elastic constants, equation of states, phonon dispersion curves, point defect properties and melting temperatures for different compositions. Even though our potential is trained on a small dataset, its accuracy is comparable to available machine learning potentials for Mo and V. Our results show that an ordered B2 phase is stable at low temperatures in alloys containing 50% V, but the solid solution phase is stable above 800 K. However, such long-range ordering is not observed in V-rich or Mo-rich alloys. In addition, our results show that V segregates to dislocation cores and grain boundaries.

The influence of cooling rate on the structure and mechanical properties of Al4CoCrCuFeNi multicomponent alloy

The present study focused on examining the composition, structure, and mechanical properties of an Al4CoCrCuFeNi multicomponent high-entropy alloy. Two states of the alloy, namely as-cast and melt-quenched, were investigated. The composition of the alloy was determined based on established criteria found in literature, which consider factors such as entropy, enthalpy of mixing, valence electron concentration, and atomic size difference of the components. To synthesize the alloy films, a splat-quenching technique was employed, where the films were rapidly cooled from the molten state. The estimated cooling rate of the films was approximately 106 K/s, calculated based on the film thickness. X-ray diffraction analysis was conducted on both the as-cast and melt-quenched Al4CoCrCuFeNi alloy samples, revealing that they exhibited an ordered B2 phase in their structure. The microhardness measurementswere carried out to evaluate the mechanical properties of the alloy. The as-cast alloy displayed a microhardness of 6500 MPa, while the melt-quenched film exhibited a significantly higher microhardness, reaching 9400 MPa.

Study on the Microstructure and Properties of FeCoNiCrAl High-Entropy Alloy Coating Prepared by Laser Cladding-Remelting

Laser remelting technology effectively repairs defects such as pores and cracks in the coating. To investigate the impact of laser remelting on high-entropy alloy coatings, this study used Q235 steel as the substrate and employed laser cladding technology to prepare FeCoNiCrAl high-entropy alloy coatings, followed by laser remelting treatment. The phase composition and microstructure of the coatings were extensively characterized using equipment such as optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Additionally, the wear resistance and corrosion resistance of the coatings were tested using a multifunctional material surface performance tester, an electrochemical workstation, and SVET (Scanning Vibrating Electrode Technique). The results indicate that following laser remelting treatment, the atomic proportion of Fe elements on the coating surface decreased from 33.21% to 26.03%, while the atomic proportion of Al elements increased from 12.56% to 20.31%. The phase composition of the coating underwent a marked transformation, shifting from a structure composed of FCC, A2, and B2 phases to a singular BCC structure characterized by the presence of A2 and B2 phases. Concurrently, the grain morphology on the coating surface transitioned from elongated plate-like grains to equiaxed grains. Laser remelting enhanced the wear resistance of the coating. Laser remelting had no significant impact on the corrosion resistance of the non-cracked regions of the coating.

Expanding the Pressure Frontier in Grüneisen Parameter Measurement: Study of Sodium Chloride.

The Grüneisen parameter (γ) is crucial for determining many thermal properties, including the anharmonic effect, thermostatistics, and equation of state of materials. However, the isentropic adiabatic compression conditions required to measure the Grüneisen parameter under high pressure are difficult to achieve. Thus, direct experimental Grüneisen parameter data in a wide range of pressures is sparse. In this work, we developed a new device that can apply pressure (up to tens of GPa) with an extremely short time of about 0.5ms, confidently achieving isentropic adiabatic compression. Then, we applied our new technique to sodium chloride and measured its Grüneisen parameter, which conforms to previous theoretical predictions. According to our obtained sodium chloride Grüneisen parameters, the calculated Hugoniot curve of the NaCl B1 phase appears up to 20GPa and 960K, which compares very well with the shock compression experimental data by Fritz etal. and other calculation works. Our results suggest that this new method can reliably measure the Grüneisen parameter of even more materials, which is significant for researching the equation of state in substances.

Unraveling solid–liquid phase transition and microstructural coarsening of semi-solid Al0.8Co0.5Cr1.5CuFeNi HEA with dual globules for thixoforming application

Multi-phase HEAs typically have potential of semi-solid processing due to wide semi-solid range. For thixoforming route of semi-solid processing (SSP), the semi-solid billet preparation by semi-solid isothermal heat treatment (SSIT) is one of the most important process steps. This work focuses on the microstructure evolution during SSIT of a semi-solid Al0.8Co0.5Cr1.5CuFeNi HEA with dual globules for thixoforming application. This semi-solid HEA contains BCC(B2), FCC globules and Cu-rich liquid film. Solidified liquid follows K-S, epitaxial orientation relationship withneighboringBCC(B2) and FCC globules. Solutionizing point for B2 phase is higher than roughly 1175 °C, and complete disordering of BCC(B2) globule occurs at 1225 °C. While, FCC globule persists stable disordered solid solution. Solid-liquid phase transition of globules provides liquid film proliferation. CALPHAD simulation on the “hypothetical” alloy system corresponding to component constitution of individual globule successfully forecasted solid–liquid phase transition. Coupling coarsening inhibition effects, including sluggish diffusion in globules, Cu-rich liquid film as inhibitory barrier, heterogeneous globule as obstacle, account for extremely sluggish microstructural coarsening (coarsening rate is only 2.44–11.25 μm3/s). Finally, through forming ofexemplar component, intriguing potential for SSP application in component manufacturing was verified.

Navigating the BCC-B2 refractory alloy space: Stability and thermal processing with Ru-B2 precipitates

Refractory multi-principal element alloys (RMPEAs) could provide next-generation high temperature alloys, but their ductility and high temperature strength need significant improvement. Emulating superalloy γ-γ’ microstructures, RMPEAs combining a ductile BCC matrix with embedded B2 precipitates for strengthening could meet this goal. Two-phase BCC-B2 RMPEAs have recently been demonstrated, but the B2 phase typically exhibits insufficient thermodynamic stability for operating temperatures ≥1300 °C.Using high-throughput CALPHAD predictions, we screen across 3,500 potential BCC-B2 systems. Promising compositions are predicted for alloys combining Ru-based B2s with refractory BCC elements. A total of 20 such compositions were arc-melted to characterize their as-cast and heat-treated microstructures. In these alloys, the RuHf B2 exhibits exceptional stability beyond 1900 °C but cannot be solutionized. By contrast, RuTi does solutionize and reprecipitate between 1300 and 1900 °C, providing a robust thermal processing pathway. RuAl can be solutionized but also tends to form competing intermetallic phases. Altogether, Ru-B2 RMPEAs offer great design flexibility and surpass the stability and thermal processability of previously studied BCC-B2 refractory alloys.

Electrical discharge machinable B4C–(Zr, Ti)B2 composites with enhanced mechanical properties

B4C30 vol% (ZrxTi1-x)B2 (x = 0.2, 0.4, 0.6 and 0.8) composites were fabricated via in-situ reaction by spark plasma sintering using B4C, ZrC, TiC and B powders as raw materials at 2000 °C. The effects of the Zr/Ti ratio in the (ZrxTi1-x)B2 phase on the microstructure and mechanical properties of the composites were investigated. The electrical discharge machining performance of the composites was evaluated. The formation of (Zr, Ti)B2 solid solutions was beneficial to fully dense composites with refined grains. The grain size of the (Zr, Ti)B2 phase first gradually decreased from 1.26 µm to 0.89 µm and then increased to 1.23 µm with the decreasing ZrC/TiC molar ratio. The material removal rate was slightly decreased from 6.56 mm3/min to 5.17 mm3/min with the decreasing ZrC/TiC molar ratio. The combined solid-solution and fine-grain strengthening has made the B4C30 vol% (Zr0.2Ti0.8)B2 composite enhanced Vickers hardness, flexural strength, and fracture toughness of 28.31 GPa, 772 MPa, and 6.56 MPa·m1/2, respectively, with a relative density of 99.73%.

Effect of microstructure and temperature on the bulk and small-scale deformation behavior of 2nd and 3rd generation advanced intermetallic TiAl alloys

Advanced intermetallic TiAl alloys have attracted considerable attention as a high-temperature structural material in aerospace and automobile sectors owing to their low density, elevated temperature strength, superior creep, and oxidation resistance. The present study is focused on assessing the effect of alloy composition, heat treatment and microstructural variation on the bulk and small-scale deformation behavior of commercial grade 2nd generation and newly developed 3rd generation TiAl alloys at 25 °C (298 K), 300 °C (573 K), and 500 °C (773 K). Twinning is noted to be the dominant deformation mechanism irrespective of the temperature. The highest yield strength and hardness are noted for the as-cast 3rd generation TiAl alloy owing to the finer microstructure and compositional variation. Heat treatment however modifies the TiAl microstructure significantly resulting to unique bilamellar-biglobular (BLBG) microstructure, devoid of the brittle β0 phase. Consequently, nano twins- and micro twins-induced enhanced deformability is noted for such microstructure, as compared to the as-cast counterparts. Interestingly, an anomalous increase in strength with an increase in temperature is observed for the studied alloys owing to the presence of high-density twins and Kear-Wilsdorf locks. Most importantly, a temperature dependant hardness anomaly is noted in the TiAl alloys that opens new avenues for further research in nanoscale deformation. This piece of research potentially strengthens the understanding of the role of constituent phases and temperature in the deformation behavior of complex TiAl alloys. Twin-induced deformation mechanism noted for the novel BLBG microstructure, can also be valid for different generations of TiAl alloys to achieve enhanced deformability that paves the way for the development of next-generation material.

The Late Bronze Age Somló Hill and a new bronze hoard

In January 2023, the National Institute of Archaeology of the Hungarian National Museum launched a new research programme, the aim of which is to explore Somló Hill (Veszprém County), which has been neglected by systematic field research focusing on the Late Bronze Age (LBA) and Early Iron Age (EIA) inhabitation of the site. In the current phase of the research programme, new, preliminary results have been provided on the settlement history of the site, primarily through a systematic metal detector survey. Based on the discovered metal objects, the south-eastern plateau of Somló Hill was inhabited primarily between the Rei Br C and Ha B2 phases, and life on the settlement was probably continuous during the Hallstatt Culture in EIA. In addition to briefly introducing our preliminary results, one of the four hoards, Hoard II from Somló Hill, is introduced. This assemblage was found by Győző Csaba Budai, a volunteer, on the once-inhabited part of the south-eastern plateau. Owing to his discovery, the in situ hoard was documented in excavation. The hoard consists of a handful of objects belonging to a few people, such as a gouge, six Lovasberény-type bracelets, three bracelets with rolled ends, two lumps, and a pseudo-winged axe. The arrangement and grouping of the objects within the assemblage reflect deliberate selection and deposition. The typo-chronological analysis of the objects from the second hoard of Somló Hill suggests that the assemblage was deposited around the younger LBA phase of the settlement in the Ha B1–Ha B2 phases.

Influence of anelastic recovery on the cyclic creep behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy

The AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) is regarded as a promising candidate for structural materials in high-temperature equipment, which may experience the cyclic creep and anelastic recovery caused by low-frequency peak-shaving loading. To investigate the influence of anelastic recovery on the microstructure and cyclic creep behavior of AlCoCrFeNi2.1 EHEA, the stress-varying (SV) tests at 800 °C are conducted to introduce the anelastic strain for comparison with the stress-constant (SC) test. The results show that the steady-state creep rate (SSCR) is accelerated with the increase in the cyclic-creep cycle and valley stress in SV tests. The anelastic recovery happened during the valley-stress holding (VSH) stage significantly alters the microstructure in the B2 phase of EHEA under SV conditions. This anelastic-recovery-related microstructural evolution is subsequently elucidated on the basis of back stress theory. Finally, the influence of microstructural evolution on the cyclic creep behaviour is revealed. The findings obtained will enhance the comprehension of high-temperature deformation mechanism of dual-phase EHEAs.

Microstructure dependence of electrochemical corrosion resistance for rapidly solidified Ti50Al48Mo2 alloy

The rapid solidification of undercooled liquid Ti50Al48Mo2 alloy was achieved by the electromagnetic levitation (EML) technique. At small and medium undercoolings, primary (βTi) dendrite reacted with surrounding liquid to drive a peritectic transformation into the (αTi) phase. The solutal Mo and Al segregations were located within the dendrite center and the grain boundary during peritectic transformation, consequently B2 phase in the dendrite center and γ phase at the grain boundary formed. Once undercooling exceeded 253 K, the peritectic transformation was completely inhibited, and the formation of the B2 phase and γ phase was completely suppressed. The ultrafine eutectoid structure was formed and a complete solute trapping effect was realized. Homogeneous solute distribution facilitated the formation of thicker passivation film with lower defect density and higher film resistance on the alloy surface. Moreover, this weakened micro-galvanic effect reduced the susceptibility to pitting corrosion, and consequently the corrosion resistance of the alloy was improved.

High strength and ductility eutectic high entropy alloy with unique core-shell structure

The as-printed AlCoCrFeNi2.1 eutectic high entropy alloys (EHEAs) alloys were manufactured from pre-alloy powders by selective laser melting (SLM) technology. The microstructure, mechanical properties and unique FCC-B2 core-shell structures of as-printed alloys were examined in detail. There are no obvious cracks, pores or defects found in as-printed alloys, and the highest relative density is more than 99.5%, showing an excellent metallurgical combination between contiguous melted layers. The as-printed alloys are consisted of FCC and B2 phases, presenting typical fish scale structures, which contain ultra-fine cellular and columnar structures, and exhibiting preferred orientation. Meanwhile, the ultimate tensile strength and elongation of the as-printed alloy manufactured by the optimum parameters are 1159.4 MPa and 29.0%, respectively. It is believed that the ultra-fine grains and unique FCC-B2 core-shell structures formed during the SLM should be responsible for such outstanding mechanical properties. In addition, the edge dislocations at the interface formed due to thermal stress are observed, while the dislocation motion has been hindered by the unique FCC-B2 core-shell structures, thereby achieving a positive combination between ductility and strength. A certain theoretical analysis value and experimental references have been provided in this work for the further application of EHEAs in additive manufacturing.

Electronic structure, optical and elastic properties of Si doped Strontium Selenide: A theoretical investigation

The structural, electronic, optical, and elastic properties of Silicon doped Strontium Selenide binary and ternary semiconductor alloys with the general form of Sr(1-x)SixSe, 0 ≤ x ≤ 1 in B1 and B3 phases have been figured adopting augmented plane wave plus local orbital methods within density functional theory, Structural properties summarize the crystal structure, relevant atomic positions, lattice constant, bulk modulus minimum energy E0 and minimum volume V0. Elastic constants conform to the structure stability of the B1 and B3 phases. Band gap is found to shift from indirect to direct and in some materials with initial direct band gap, the gap width increased which increased the range of applicability of these binary and ternary semiconductor compounds. Whereas optical properties which include the study of zero frequency limit of static dielectric constant ε0(ω) with its real and imaginary parts, static refractive index n(0), optical reflectivity (R), optical absorption coefficient (α), and loss function (L) studied comprehensively to get real electrical and optical properties of these materials and give semiconductor market best alternative candidate which shows its effectiveness in the visible, ultraviolet and infrared region of the electromagnetic spectrum. The obtained results were compared together and with the available experimental along with theoretical work on these binary and ternary Silicon doped Alkaline earth chalcogenides.

Lightweight Al3Ti-based medium-entropy alloys with well-balanced strength and ductility

The lightweight Al3Ti intermetallic compound shows superior properties at elevated temperatures but its room-temperature brittleness largely limits its usefulness. We propose Al3Ti-based lightweight medium-entropy alloys (MEAs) with selected alloying elements, which change Al3Ti from a tetragonal D022 structure to a ductile cubic L12 one with embedded hard B2 and D8a phases. A combination of improved ductility and strength can be achieved. Four lightweight AlTiCrMnFeCu MEAs (ρ=3.65∼4.27 g/cm3) with tunable balance between hardness and ductility were fabricated. Ti and Fe promoted the formation of hard B2 phase, while Cr and Mn favored the formation of D8a phase which strengthened the alloy at the minor expense of ductility. The compressive yield and peak strengths of the MEAs e.g., Al55Ti20Cr5Mn10Fe5Cu5, can reach as high as 650 MPa and 1366 MPa, respectively, with its fracture strain around 17 %. This study provides useful information for designing Al3Ti-based lightweight MEAs with desirable properties.

Elastocaloric Effect and Magnetic Properties of Cu–Al–Mn Shape Memory Alloy

Herein, the magnetic properties and elastocaloric effects of Cu70Al19 + 0.5xMn11−0.5x (x = 0, 1, 2, 3) alloys are investigated. The resistance versus temperature curves indicate that the phase transition temperature increases as the Mn content decreases. In particular, the Cu70Al20.5Mn9.5 alloy exhibits a phase transition temperature close to room temperature. Therefore, the elastocaloric effects of this alloy are examined under stresses ranging from 200 to 500 MPa. The results show that the adiabatic temperature change of the alloy under a stress of 500 MPa reaches 9.8 K. Furthermore, the magnetization curves at 300 K reveal that the magnetic properties of the alloy significantly improve after undergoing low‐temperature aging treatment. The X‐ray diffraction patterns show that this improvement can be attributed to the transformation of the β1 phase to the ferromagnetic phase β3. Overall, the Cu70Al20.5Mn9.5 alloy demonstrates elastocaloric and magnetic properties comparable to those observed in certain Ni–Mn‐based alloys.