Search

Spherical powders are required for many advanced manufacturing techniques due to their inherent requirement of flowability, either within feed tubes or during powder spreading. As advanced manufacturing of magnets continues to develop, new production methods for feedstocks are also sought. Plasma spheroidization is a high-yield method to produce spherical Nd–Fe–B powders from irregularly shaped particles, with advantages including high throughput and a well-controlled size distribution. Highly spherical Nd–Fe–B powders with large scale production (i.e., kg) have been demonstrated using an inductively coupled thermal plasma system; however, the magnetic properties of the output powder display significant degradation. The coercivity was decreased from the initial 8 kOe (636 kA/m) of the as-received to 0.7 kOe (55 kA/m) for spheroidized powders. Microstructural investigation reveals 6% Nd depletion caused by the extreme temperatures of the plasma, leading to the formation of low-coercivity α-Fe and a subsequent decrease in energy product. Post-spheroidization heat treatments with Nd can partially mitigate the coercivity degradation, increasing to 1.7 kOe (135 kA/m), potentially offering a pathway toward spherical powders for a range of applications. [ABSTRACT FROM AUTHOR]

Theoretical and experimental approaches have been employed for studying the lattice site occupation effect on the electronic structure and some physical properties of CoMnCrAl Heusler alloy (HA). Among possible variants of the ordered stoichiometric CoMnCrAl HA lattice site occupation by Co, Mn, Cr, and Al atoms, the first-principle calculations have been performed for three nonequivalent ones (marked by us as type 1, type 2, and type 3, respectively). CoMnCrAl HA with atomic order of the first type is half-metallic ferromagnet (FM) with resulting magnetic moment of m t o t 1 = 0.9999 μ B /f.u. and spin-polarization degree of Fermi electrons P 1 = 100 % , for atomic orders of second and third types, m t o t and P are equal to m t o t 2 = 1.0186 μ B /f.u., P 2 = 89 % and m t o t 3 = 6.8673 μ B /f.u., P 3 = 77 % , respectively. Changes in the order type on the way T1 → T2 → T3 cause a decrease in the spatial electron density, weakening of the covalent chemical interatomic bonds, lead to a decrease in the cohesion energy E c o h and hence to loss of the thermodynamic stability of the CoMnCrAl alloy. Despite various high-temperature heat treatments, only B2- and A2-types of atomic order have been obtained in bulk and film CoMnCrAl alloy samples. Experimentally, it was found that bulk B2-type ordered CoMnCrAl alloy demonstrates significantly lower magnetization [ M (300 K) = 0.442 μ B /f.u.] and spin-polarization degree of Fermi electrons [ P ≈ 30 % ] than theoretically predicted. More disordered crystalline CoMnCrAl films with A2-type of atomic order practically are non-FM at T = 300 K with P = 0. [ABSTRACT FROM AUTHOR]

In the present work, we study the effect of quenching and annealing on the ferroelectric and piezoelectric properties at room temperature and elevated temperatures of a new ternary BiFeO3-PbTiO3-Li0.5Bi0.5TiO3 bulk piezo ceramic. While sacrificing part of the maximally obtainable piezoelectric constant value, using an optimal heat treatment, a quasi-stable value for the piezoelectric constant of 65 pC/N was obtained irrespective of the annealing temperature. All experimental results point to the direction of unusual defect behavior in this novel ternary system leading to a well-defined metastable state. The quenching and annealing process are completely reversible and can be used in combination with additional chemical modifications to tailor the properties of this new high-temperature piezoelectric ceramic to the intended use conditions. [ABSTRACT FROM AUTHOR]

In this manuscript, perovskite oxide LaCoO3/LaMnO3/LaCoO3 (LLL) trilayers and the single-layer LaMnO3 (LMO) and LaCoO3 (LCO) films are epitaxially grown on (001)-oriented SrTiO3 substrates by polymer-assisted deposition combining with heat treating in Ar, air, and O2 atmospheres, respectively. The crystal structure and magnetic properties are investigated. It is found that the responses of LMO and LCO films to oxygen content are different, and the magnetic property of LMO is more sensitivity to oxygen content than that of LCO. The oxygen content can directly affect the structure and magnetic properties of LMO and LCO layers, which, in turn, modulate the interfacial magnetic properties of the LLL trilayers through interlayer coupling. By comparison with the magnetic properties of the single-layer films, an abnormal ferromagnetic (FM) transition is found in the LLL trilayers at around 216 K, besides two known FM transitions corresponding to those in the LCO and LMO layers, respectively. It is suggested that the abnormal FM transition is attributed to Mn4+–O–Co2+ FM super-exchange interaction, which is induced by the charge transfer from Mn3+ to Co3+ ions and the interlayer coupling between the LMO and LCO layers. The interlayer coupling of the trilayers, including the interfacial coupling and the diffusion-induced inlayer coupling, dominates the interface properties, which are tuned by oxygen content-dependent charge transfer. The cooperative function of the orbital/charge structure and the interlayer coupling dominates the magnetic properties of the LLL trilayer under the tensile strain. These findings provide new avenues to regulate the electronic and magnetic states of perovskite oxide multilayers and another way to the development of multifunctional electronic devices. [ABSTRACT FROM AUTHOR]

In this study, influence of SbCl3 treatment on CdTe films deposited by the close space sublimation method was investigated. SbCl3 treatment was compared with conventional CdCl2 treated and untreated samples. It was determined that CdTe grew as Cd-rich and there was a slight decrease in Cd-amount after SbCl3 and CdCl2 treatments. In addition, a significant amount of Sb was detected in the SbCl3 treated sample. The samples crystallized in the cubic structure of CdTe. However, graded structures such as phase-I and phase-II with different structural parameters were formed. In the SbCl3 sample, it was revealed that the presence of Sb- caused a slight increase in the lattice parameter, compared to the other samples. Morphological analyses of the samples showed facet and large-small grain structures. CdCl2 treatment caused a slight decrease in grain size, while SbCl3 treatment resulted in a coarser and rougher grain structure. CdCl2 treatment increased transmittance, whereas SbCl3 treatment caused a decrease in transmittance (hence, an increase in absorbance). It was observed that the bandgaps were ∼1.49 eV in all samples, and annealing, as well as CdCl2 and SbCl3 heat treatments did not cause a sharp change in the bandgaps. Photoluminescence spectra revealed the presence of band-edge and shallow-level defect transitions (except CdCl2 treated) in the samples. All results suggest that SbCl3 heat treatment has a significant effect on CdTe and may be an alternative to CdCl2. [ABSTRACT FROM AUTHOR]

With the development of modern industry, the discharge of dye wastewater is increasing year by year, and the damage caused by this wastewater to the ecosystem is often irreversible. Therefore, the research on the harmless treatment of dyes has attracted much attention in recent years. In this paper, commercial titanium dioxide (anatase nanometer titanium dioxide) was heat treated with anhydrous ethanol to synthesize titanium carbide (C/TiO2). Its maximum adsorption capacity for cationic dyes methylene blue (MB) and Rhodamine B is 27.3 and 124.6 mg g−1, respectively, which is much higher than that of pure TiO2. The adsorption kinetics and isotherm model of C/TiO2 were studied and characterized by Brunauer–Emmett–Teller, x-ray photoelectron spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and other methods. The results show that the carbon layer on the surface of C/TiO2 promotes the increase in surface hydroxyl groups, which is the main reason for the increase in MB adsorption. Compared with other adsorbents, C/TiO2 showed excellent reusability. The experimental results of adsorbent regeneration showed that the adsorption rate R% of MB was almost unchanged after three cycles. During the recovery of C/TiO2, the dyes adsorbed on its surface are removed, which solves the problem that the adsorbent cannot degrade dyes simply by adsorption. Additionally, C/TiO2 has a stable adsorption effect, is insensitive to the pH value, has a simple preparation process, and has relatively low raw material prices, making it suitable for large-scale operation. Therefore, it has good commercial prospects in the organic dye industry wastewater treatment. [ABSTRACT FROM AUTHOR]

Herein, we investigate the influence of heat treatment on microstructure and thermo-physical properties of Al-50wt%Si alloy fabricated by selective laser melting (SLM). Microstructure characterizations reveal that SLM and heat-treated Al-50wt%Si alloys are all characterized by the primary Si and eutectic structure consisting of dominant Al matrix and tiny eutectic Si. However, the size of primary Si monotonously increases with increasing the heat treatment holding time at 550 °C. In addition, the SLM Al-50wt%Si alloy displays a highest coefficient of thermal expansion (CTE) among all examined alloys. As the heat treatment holding time increases, the Si precipitates from the Al(Si)-supersaturated solid solution, leading to the formation of a skeleton-like Si phase, which effectively alleviates the thermal expansion. Furthermore, the SLM Al-50wt%Si alloy exhibits a lowest coefficient of thermal conductivity (CTC), since the significantly increased size of primary Si with increasing the heat treatment holding time leads to a substantial reduction in the number of grain boundaries, which severely restricts the scattering of heat transfer phonons. Moreover, theoretical models are employed to calculate the CTE and CTC. Results indicate that the Schapery lower model provides a better prediction of CTE, and the actual CTC values of Al-50wt%Si alloys after heat treatment are closer to theoretical values. These findings can provide new insights into designing Al matrix composites with low CTE and high CTC through microstructural optimization.

The present study investigated the effects of heat treatment (solid solution and aging treatments) on the microstructure and mechanical properties of a hot-rolled α+β Ti–3Al–5Mo–4.5V (TC16) produced through blended elemental powder metallurgy (BEPM) process using master alloy hydrogenation (MAH) approach. After solid solution treatment, metastable martensite α'' phase and athermal ω phase were formed. Aging treatment facilitated decomposition of metastable phases and precipitation of αs particles. Dispersion strengthening, resulting from the formation of a significant amount of α/β interfaces between fine secondary αs particles and β matrix, played a decisive role in enhancing the strength of the TC16 alloy. However, elevated aging temperatures promoted the coarsening of αs particles, leading to a reduction in the strengthening effect. A systematic investigation of the effects of the solid solution and aging treatments enabled the evolution of a bimodal microstructure with the precipitation of fine αs particles, contributing to an outstanding combination of strength and ductility. The ultimate tensile strength reached 1424.6 MPa with an elongation at break of 7.7%, while the hardness reached 380.2HV.

We investigated the impact of heat treatment on preform deduction during the hot forging of In718 turbine disks. Proposed preform design method leverages a Convolutional Neural Network (CNN) to aim for minimized damage and uniform grain size in the final forged products. For damage calculation, we employ the Lemaitre damage model, while the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model is utilized for grain size calculation. The CNN, trained on datasets of NURBS-generated preform shapes and final forged disks from them, showed superior performance in terms of damage and grain size of forged disk compared with other existing approaches. Moreover, the results indicate that preforms deduced with heat treatment considerations can lead to significant improvements in forging results, including up to a 17% reduction in average grain size and a 16% decrease in standard deviation compared to preforms without heat treatment consideration. These results underscore the importance of considering heat treatment in preform design, offering valuable insights for industries where the integrity of forged products, like aerospace, is critical.

In the recycling process, aluminum scraps, characterized by a considerable specific surface area, yield a remelt abundant in inclusions. While advanced melt purification systems proficiently extract hydrogen and large inclusions, micron-sized inclusions remain challenging to remove. Despite previous findings suggesting nominal effects of inclusions on the microstructure and properties of aged 7xxx-series plates, the products' airworthiness demands further improvement. This research aims to decipher the influence of micron-sized inclusions on the microstructure and properties of recycled 7xxx aluminum alloy. We prepared thin sheets of varied cleanliness and utilized SEM, EBSD, and TEM to characterize their microstructure at different heat treatment stages. Additionally, high-temperature tensile and bending properties, together with exfoliation corrosion behaviors, were examined. Our results point to the causative role of inclusions in localized dislocation accumulation post-rolling, which annealing can mitigate but not fully eliminate; however, a solid solution can effectively address this issue. The inclusions significantly disrupt the microstructure and properties of the annealed recycled sheet, but their impact on the solid solution-aged recycled sheet is minor. This study's findings can guide the high-end transformation of recycled aluminum alloy and lay a theoretical foundation for sustainable aluminum recycling.

The heterostructured Al–Mg–Si–Cu alloy profile modified by TiB2–TiC particles was prepared by conventional extrusion and solution treatment, and the coupling effect of the heterostructure and the precipitates on the mechanical properties of the alloy profile was studied in this work. The results showed that the peak-aged alloy sample has high tensile strength (385 MPa) and yield strength (366 MPa) with low elongation (4.8%), while the pre-aged sample achieves higher tensile strength (426 MPa), yield strength (401 MPa), and also the elongation (8.0%). The better comprehensive mechanical properties of the pre-aged sample were attributed to the synergistic strengthening effect of precipitation strengthening and hetero-deformation induced (HDI) stress strengthening. The fine precipitates easy to shear in pre-aged sample are more advantageous than the precipitates in peak-aged sample for the heterostructured Al alloy, because they provided precipitation strengthening by hindering the slip of dislocations and did not prevent the accumulation of geometrically necessary dislocations (GNDs) resulting in HDI strengthening and HDI strain hardening. This work provides a new strategy for promoting the comprehensive mechanical properties of age-hardenable aluminum alloy with heterogeneous structure.

In this paper, a high-entropy AlCoCrFeNi alloy were prepared using laser melting deposition (LMD) and the effect of heat treatment on their microstructure and corrosion resistance was studied. XRD, OM, SEM, EDS, EBSD and electrochemical tests were used to investigate the structure, microstructure, and corrosion resistance. The LMD and LMD-500 °C samples showed a single BCC phase structure. After the temperature was increased to 800 °C, a small amount of a Cr-rich and Fe-rich FCC phase and σ phase precipitated at the grain boundaries, Al and Ni were enriched within the crystals. At 1100 °C, the σ phase disappeared, and the FCC phase content increased from 1.4% to 5.2%. The average grain size was the largest at 500 °C, reaching 31.29 μm. In 3.5% NaCl solution, the LMD-500 °C sample showed a high self-corrosion potential and the lowest corrosion current density; the polarization resistance (Rp) and charge transfer resistance (Rct) were 5.266 × 105 Ω∙cm2 and 1.248 × 108 Ω∙cm2, respectively, with the shallowest surface corrosion and the best corrosion resistance. In 0.5 mol/L NaOH solution, there were only a few corrosion holes in the samples before and after the heat treatment, and all the samples showed a good corrosion resistance. In 0.5 mol/L H2SO4 solution, with the increase of temperature, the Cr, Al and other elements underwent intensified segregation. The corrosion resistance gradually improved, the Rp and the Rct was 2.785 × 102 Ω∙cm2 and 7.569 × 103 Ω∙cm2, respectively, at 1100 °C, providing the best corrosion resistance.

The effects of solid solution temperature, aging temperature and aging cooling rate on the microstructure evolution of forged Ti-22.5Al-24.7Nb (at. %) alloy were investigated. With the increasing solid solution temperature, the number of equiaxed microstructure first increases and then decreases, reaching the maximum at 900 °C. Lamellar microstructure solubilizes in the matrix or gradually becomes coarser and shorter, and transforms into equiaxed microstructure. When the solution temperature is 1000 °C, equiaxed α2 phase gradually changes to be lath-shaped and concave. During the aging process, some α2 phase transforms into O phase, and the aging temperature affects the shape of equiaxed microstructure and the spacing between the needle-like microstructure. With the increasing aging temperature, the number of equiaxed microstructure increases linearly, and the proportion of fine secondary O phase decreases while the thickness increases. The lamellar morphology of O phase can be retained at a faster cooling rate, while a portion of lamellar O phase is converted to the B2 phase after furnace cooling. Through heat treatment, the volume fraction and the size of lamellar O phase could be well controlled.

In this study, a Ni50.4Ti49.6 shape memory alloy (SMA) was fabricated by selective laser melting (SLM), and it is found that heat treatments were effective to change the phase transformation behavior, microstructure, and superelasticity under compression for SLM Ni50.4Ti49.6. Detailed results based on EBSD demonstrated that, for SLM Ni50.4Ti49.6 during solid solution and aging (450 °C) treatment, the ultrafine cellular and columnar grains (∼16.5 μm) in as-fabricated Ni50.4Ti49.6 became equiaxed grains (∼70.2 μm), and the frequency of low-angle grain boundaries (26.7%→13.5%) and kernel average misorientation (0.37 → 0.21) decreased. The SEM and TEM analyses show that Ti-rich Ti2Ni/Ti4Ni2Ox and Ni-rich Ni4Ti3 precipitate phases were formed in the matrix simultaneously. After solid solution treatment, the size and distribution of Ti2Ni/Ti4Ni2Ox almost unchanged with aging temperature increasing from 350 °C to 550 °C, however, the size of Ni4Ti3 in aging-treated NiTi samples increased with aging temperature obviously, and it is interesting to find that the distribution of Ni4Ti3 became uneven and dislocation networks were formed in the matrix when the aging treatment reached up to 550 °C, which originated from the internal stress generated by supersaturated Ni atoms. Furthermore, the results of superelasticity for aging-treated NiTi demonstrated that the characteristics of Ni4Ti3 precipitate phase were powerful to influence the process of superelasticity decay/fatigue instead of determining the ultimately recovery strain after 10 compressive cycles. The aging-treated NiTi with evenly-distributed, high-density, and relatively-small Ni4Ti3 precipitate phase shows minimum recovery strain at 1st cycle compression and best superelasticity stability among three aging-treated NiTi, which was attributed to strong obstruction effect of these Ni4Ti3 precipitate for the occurrence of stress-induced martensitic transformation process and formation of dislocations. In contrast, the aging-treated NiTi with unevenly-distributed and low-density Ni4Ti3 precipitate shows maximum recovery strain at 1st cycle compression and worst superelasticity stability. These results in this work can bring some meaningful insights into tailoring the microstructure and superelasticity of SLM NiTi SMAs.

Al-3.4Mg-1.7Si alloy single-pass and multi-layer thin wall components were fabricated with double wires + arc additive manufacturing procedure. Heat treatment was performed to further process the component. The microstructure and mechanical properties of the as-deposited and heat-treated components were comparatively investigated. After heat treatment, the grains grow up slightly, and the phase particles change to distribute semi-continuously, and a large number of nanoscale monoclinic β″ precipitated phases generate. The porosity increases to 0.0486% from as-deposited 0.0348%. The microhardness, ultimate tensile strength and yield strength are respectively improved by 25%,79%, and 228% with heat treatment process, with the hardness uniformity and elongation decreased.

High-density MX precipitates block the movement of dislocations during creep at high temperature and increase sink strength to point defects under irradiation. Therefore, the precipitation control of MX phase is crucial for the advancement of reduced activation ferritic/martensitic (RAFM) steels. In this paper, an optimized two-step austenitizing strategy was proposed to enhance Ta(C, N) precipitation in RAFM steels, and the temperature effects of the first and second austenitizing on the Ta(C, N) precipitation enhancement were studied. During the first austenitizing, Ta(C, N) particles with a small radius (∼12 nm) and a high number density (∼8.5 × 1019 m−3) precipitated by heterogeneous nucleation on the M23C6 phase boundaries retained by the comparatively low temperature (900 °C). Then in the second austenitizing, enhanced Ta(C, N) precipitates kept good size and thermal stability below 1050 °C. Compared to RAFM steels treated by conventional normalizing and tempering, the strength and creep performance were significantly improved by the pinning effect of the enhanced dispersed Ta(C, N) particles. Furthermore, the optimized two-step austenitizing strategy was validated in the other two RAFM steels, showing broad application prospects in RAFM and heat-resistant steels.

The transformation of shape-memory alloys to high-temperature shape-memory alloys can be achieved through either the addition of alloying elements or heat treatment. However, heat treatment is more effective in improving the properties of the alloys. This research paper explores the impact of annealing on the mechanical and shape memory properties of Cu–Al–Ni shape memory alloys. The alloys were first cast, homogenized, and then machined before being aged at temperatures of 250, 300, and 350°C, and finally air-cooled. The results showed an increase in transformation temperature and recovery strain, as well as shape memory effect, and a decrease in hardness. Moreover, there was an increase in yield stress and strain. In conclusion, aging was found to improve the shape memory properties and mechanical properties better than thermomechanical treatment and some alloying elements.

This study aimed to investigate the metallographic structure and the impact of the heat treatment process on the MAR-M247 superalloy, a high-temperature nickel-based superalloy commonly used in turbine blades. The heat treatment process can potentially influence the mechanical properties of the MAR-M247 superalloy at different temperatures. A strength simulation analysis of gas turbine blades should include the variations in the mechanical properties of the material. The effect of heat treatment on grain size was investigated by metallographic experiments, and numerical calculations of material mechanical properties were conducted. The mechanical property parameters necessary for finite element analysis of turbine blades were determined. Finally, a finite element simulation model of the blade was established based on these mechanical property parameters, and strength analysis was performed. The simulation results provided the stress distribution and the strength of the turbine blade.

Inconel 625 is typically used in extreme environments due to excellent mechanical properties such as high strength, corrosion resistance, abrasion resistance and low-temperature toughness. When manufacturing a hot forged flange with a thick and complex shape, the cooling rate varies depending on the location due to the difference in thermal gradient during the cooling process after hot forging. In this study, to evaluate the microstructure and mechanical properties of Inconel 625 according to the cooling rate, we performed heat treatment at 950°C, 1050°C, and 1150°C for 4 hours followed by water cooling. Additionally, temperature data for each location on the flange were obtained using finite element method (FEM) simulation for each heat treatment temperature, revealing a discrepancy in the cooling rate between the surface and the center. Therefore, the correlation between microstructure and mechanical properties according to cooling rate was investigated.