Subsequent Heat Research Articles

Investigation of phase and microstructural transformations in different alumina-silica fibers at varied heat treatment temperatures: Exploring the mechanism of Silica's influence

The study investigated the phase transformation and microstructural comparison of two types of continuous alumina fibers with varying silica contents. These fibers were subjected to heat treatment at temperatures of 1100, 1200, 1300, and 1400 °C in air. By comparing the experimental results of the two different fibers, relevant influencing mechanisms were derived. The appearance of mullite phase in the fibers occurred when the heat treatment temperature reached 1200 °C. Variations in silicon content led to inconsistent pinning effects, resulting in differences in the occurrence of irregular structures on the surface of the two types of fibers. Following heat treatment at 1300 °C, the fibers exhibited scale-like and mosaic-like structures, accompanied by phase aggregation. Subsequent heat treatment at 1400 °C resulted in the fibers displaying layered structures composed of α-Al2O3 phase and undergoing significant changes in microstructure. Notably, the two types of fibers exhibited a significant difference in the presence or absence of a glass phase, and the addition of silicon oxide to a certain extent was found to inhibit the crystal transformation of Al2O3. Additionally, the experimental results were analyzed in terms of influencing mechanisms based on theories such as activation energy barriers and total free energy.

Graphene nanoribbon hydrogel scaffold for highly conductive and robust polyimide nanocomposite

Although highly loaded graphitic nanocarbon materials effectively enhance the electrical, mechanical, and thermal properties of polymeric materials, their practical implementation has been hindered by severe aggregation issues. Here, we propose a method to achieve homogeneous nanocarbon-polyimide (PI) composites by integrating graphene oxide nanoribbons (GONRs) with polyamic acid ammonium (PAA) salt, a precursor of PI. Self-assembled scaffold structure of GONRs hydrogel enables the uniform integration and immobilization of PAA within the GONR scaffold, mitigating aggregation concerns. The resulting GONR/PAA hydrogel, formed through physical interactions, can be coated onto substrates via a shear stress-induced bar coating method due to its viscoelastic rheological properties. Subsequent heat treatment at 400 °C triggers the imidization reaction of PAA and the reduction of GONR, facilitating the formation of uniformly integrated GNR/PI nanocomposite coatings. Under optimized conditions, incorporating a high-loading GONR content in PAA (95 wt% of GONR and 5 wt% of PAA) yielded GNR/PI composites with excellent mechanical properties, exhibiting a hardness of 0.75 GPa and an elastic modulus of 8.3 GPa. Additionally, this GNR/PI composite displayed a good electrical conductivity of 3890 S/m, attributed to the electrical pathways formed by GNRs within the PI matrix.

Morphological evaluation of β-Ti-precipitation and its link to the mechanical properties of Ti–6Al–4V after laser powder bed fusion and subsequent heat treatments

The microstructural properties of additively manufactured Ti–6Al–4V depend strongly on the heat treatment after Laser Powder Bed Fusion. Among others the evaluation of morphological characteristics of β-Ti precipitates allows a fast and objective way to distinguish between different metallurgical conditions with different mechanical properties based on an automated analysis of high-resolution SEM images. High temperature heat treatment and hot isostatic pressing improve the mechanical properties while also reducing the scattering of results, leading to better predictable performance. Similar and subjectively not distinguishable microstructural conditions are observed after applying low temperature heat treatments of different sample batches with comparable UTS of app. 1100 MPa but very different elongation at break between 0.3 % and 6.5 %. Advanced classification methods based on machine learning and classical statistics allow a reliable distinction of almost identical microstructural conditions. Their specific characteristics in terms of required expert domain knowledge, general performance and interpretability of their results are discussed.

Stabilization of porosity in reaction bonded aluminum oxide (RBAO) by coarsening in a reactive atmosphere

A coarsening treatment in an HCl containing atmosphere was performed to stabilize the porosity of Al2O3/ZrO2 composites up to elevated temperatures. There is minimal shrinkage during the reactive coarsening treatment and the porous microstructure is stable during subsequent heat treatments. The reaction bonding of aluminum oxide (RBAO) process was used to fabricate the samples. Coarsening was investigated as a function of initial density (40–60 % TD) and coarsening temperatures (1250–1400 °C). After the HCl coarsening step, samples were sintered in air to determine the effect of coarsening treatment on pore stability. Up to the temperature of the coarsening treatment no further densification is observed. Above the HCl coarsening temperature densification is significantly retarded. Thus, it is shown that the porosity in RBAO can be stabilized by heat treatment in a 10 vol % HCl containing atmosphere. During the coarsening treatment in HCl at 1300 °C, 1350 °C and 1400 °C little densification was observed (Δ ρ ≤ 2 % TD) in comparison with the densities that result from sintering reaction bonded samples in air at 1350 °C (Δ ρ ∼ 5–8 % TD). Therefore, the HCl coarsening is a promising approach to adjust a desired level of porosity for high temperature applications of porous materials. It is postulated that at a given density, the coarsened materials should exhibit increased strength compared to un-coarsened materials due to increased contact area between the particles.

Histone H3.3 chaperone HIRA renders stress-responsive genes poised for prospective lethal stresses in acquired tolerance.

Appropriate responses to environmental challenges are imperative for the survival of all living organisms. Exposure to low-dose stresses is recognized to yield increased cellular fitness, a phenomenon termed hormesis. However, our molecular understanding of how cells respond to low-dose stress remains profoundly limited. Here we report that histone variant H3.3-specific chaperone, HIRA, is required for acquired tolerance, where low-dose heat stress exposure confers resistance to subsequent lethal heat stress. We found that human HIRA activates stress-responsive genes, including HSP70, by depositing histone H3.3 following low-dose stresses. These genes are also marked with histone H3 Lys-4 trimethylation and H3 Lys-9 acetylation, both active chromatin markers. Moreover, depletion of HIRA greatly diminished acquired tolerance, both in normal diploid fibroblasts and in HeLa cells. Collectively, our study revealed that HIRA is required for eliciting adaptive stress responses under environmental fluctuations and is a master regulator of stress tolerance.

Micropattern Fabricated by Acropetal Migration Controlled through Sequential Photo and Thermal Polymerization.

Bottom-up patterning technology plays a significant role in both nature and synthetic materials, owing to its inherent advantages such as ease of implementation, spontaneity, and noncontact attributes, etc. However, constrained by the uncontrollability of molecular movement, energy interaction, and stress, obtained micropatterns tend to exhibit an inevitable arched outline, resulting in the limitation of applicability. Herein, inspired by auxin's action mode in apical dominance, a versatile strategy is proposed for fabricating precision self-organizing micropatterns with impressive height based on polymerization-induced acropetal migration. The copolymer containing fluorocarbon chains (low surface energy) and tertiary amine (coinitiator) is designed to self-assemble on the surface of the photo-curing system. The selective exposure under a photomask establishes a photocuring boundary and the radicals would be generated on the surface, which is pivotal in generating a vertical concentration difference of monomer. Subsequent heating treatment activates the material continuously transfers from the unexposed area to the exposed area and is accompanied by the obviously vertical upward mass transfer, resulting in the manufacture of a rectilinear profile micropattern. This strategy significantly broadens the applicability of self-organizing patterns, offering the potential to mitigate the complexity and time-consuming limitations associated with top-down methods.

A novel nickel-based superalloy with excellent high temperature performance designed for laser additive manufacturing

The nickel-based superalloys prepared by additive manufacturing (AM) commonly exhibit inferior mechanical properties at high temperatures, particularly in terms of ductility and creep resistance, compared to the corresponding conventional manufactured (CM)alloys, and this significantly hinders the widespread application of AM nickel-based superalloys in the aerospace industry. To address this problem, a novel nickel-based superalloy for additive manufacturing, Hastelloy X-AM (HX-AM), using the yttrium (Y) alloying strategy has been developed in this work. The results show that the Y element is present in the matrix as Ni5Y phase and yttrium oxide nanoparticles after laser additive manufacturing, exerting a significant inhibitory effect on the precipitation and coarsening of detrimental second phases at grain boundaries (GBs) during subsequent heat treatment or service processes. The HX-AM alloy exhibits an exceptional matching relationship between strength (ultimate tensile strength = 315 ± 3 MPa) and ductility (total elongation = 56 ± 1.7 %) at 900 °C. What's more, the creep performance of HX-AM alloy is significantly improved simultaneously compared with CM Ni-based alloys at 900 °C, overcoming the longstanding challenge of inferior creep performance in AM nickel-based superalloys at high temperature. The fatigue lifetime of HX-AM alloy reaches 295.6 h at 900 °C/40 MPa, showing over fifteenfold enhancement compared to that of CM Hastelloy X alloy.

Ultralight Hierarchical Fe3O4/MoS2/rGO/Ti3C2Tx MXene Composite Aerogels for High-Efficiency Electromagnetic Wave Absorption.

Aerogel-based composites, renowned for their three-dimensional (3D) network architecture, are gaining increasing attention as lightweight electromagnetic (EM) wave absorbers. However, attaining high reflection loss, broad effective absorption bandwidth (EAB), and ultrathin thickness concurrently presents a formidable challenge, owing to the stringent demands for precise structural regulation and incorporation of magnetic/dielectric multicomponents with synergistic loss mechanisms within the 3D networks. In this study, we successfully synthesized a 3D hierarchical porous Fe3O4/MoS2/rGO/Ti3C2Tx MXene (FMGM) composite aerogel via directional freezing and subsequent heat treatment processes. Owing to their ingenious structure and multicomponent design, the FMGM aerogels, featured with abundant heterogeneous interface structure and magnetic/dielectric synergism, show exceptional impedance matching characteristics and diverse EM wave absorption mechanisms. After optimization, the prepared ultralight (6.4 mg cm-3) FMGM-2 aerogel exhibits outstanding EM wave absorption performance, achieving a minimal reflection loss of -66.92 dB at a thickness of 3.61 mm and an EAB of 6.08 GHz corresponding to the thickness of 2.3 mm, outperforming most of the previously reported aerogel-based absorbing materials. This research presents an effective strategy for fabricating lightweight, ultrathin, highly efficient, and broad band EM wave absorption materials.

Indirect magneto-ionic effect in FeSi2/Si nanocomposite induced by electrochemical lithiation and delithiation

A nanocomposite consisting of iron disilicide nanocrystals embedded in a Si matrix was prepared from industry-grade ferrosilicon by ball milling and subsequent heat treatment. By tailoring the heat treatment temperature either the metallic α-FeSi2 or the semiconducting β-FeSi2 phase could be made the dominant one, as indicated by x-ray diffraction. Magnetization curve and zero-field cooled/field cooled measurements revealed that ferromagnetic and superparamagnetic centers are present in the nanocomposites, which could be attributed to Fe-rich defective regions at the surface of the iron disilicide nanocrystals. For both nanocomposites, containing either mainly the α or β phase, we could show that the magnetization can be varied by about 40% by electrochemical lithiation and delithiation of the surrounding Si matrix, with up to 6.5% of the magnetization change being reversible. These variations could be attributed to the formation of additional Fe-rich magnetic regions, induced by a local change of the Fe/Si fraction at the FeSi2/Si interfaces, and their subsequent partial elimination. Thus, this work demonstrates a new concept for how an ‘indirect magneto-ionic effect’ can be obtained in composite materials consisting of a phase prone to the electrochemical ion uptake (i.e. the Si matrix) and a magnetic phase (i.e. the FeSi2 nanocrystals).

Structure and mechanical properties of Ti2AlNb-based alloy welded joints using keyhole plasma arc welding with subsequent heat treatment

Using keyhole plasma arc welding, welded joints of a Ti2AlNb-based alloy, VTI-4, were obtained, and their structure and mechanical properties were studied. It has been established that the dynamic effect of a keyhole arc had a positive effect on the quality of the welded joint; namely, lack of penetration, porosity, and microcracks were eliminated. The welded joint consisted of a fusion zone (FZ), a heat-affected zone (HAZ), and a base metal (BM). Depending on the phase composition and morphology of the obtained phases, the HAZ can be divided into four zones: HAZ1 with large β-phase grains near the melting line, HAZ2 with large β-phase grains + α2, HAZ3 with more fragmented β-phase grains retaining more α2-phase, and HAZ4 with the phase composition β + α2 + O. Subsequent heat treatment (HT: quenching at 920 °C for 2 h, cooling in air, followed by aging at 800 °C for 6 h, cooling in air) preserved the zone structure of the weld but led to the formation of the O-phase within β-grains. The microhardness of the weld in the zone corresponds to 360±15 HV0.2, but after HT, it increased to 382±20 HV0.2. The strength properties of the welded joint after HT were above 90 % of the base metal (σucs = 1120 MPa, σ0.2 = 1090 MPa), while elongation to failure is close to the initial condition (δ = 2.1 %).

EFFECT OF PRECIPITATION HARDENING ON MICROSTRUCTURE OF 17-7 PH STEEL WITH MODIFIED CHEMICAL COMPOSITION

<p>Steel 17-7PH is austenitic-martensitic steel with high strength, hardness, and resistance to creep, and<br />corrosion. It is designed for aerospace components, but can also be used for other applications that require<br />high strength and corrosion resistance, as well as leaf springs for operation at temperatures up to 316 °C. It<br />can be used in a solution-treated or heat-treated state to obtain a wide range of property values. This<br />paperwork shows that modification of the contents of alloying elements with a narrower interval of Cr, Ni,<br />and Al can be obtained from austenitic-martensitic steel 17-7PH which by, a subsequent heat treatment,<br />can have values of mechanical and chemical properties required for components of an automotive engine.<br />Chromium is an alphagenic alloying element that stabilizes the ferrite region, nickel is a gammagenic<br />alloying element that stabilizes austenite and gives these steels good strength and toughness, even at low<br />temperatures and aluminum increases corrosion resistance in low-carbon corrosion-resistant steels<br />Research has determined the most suitable interval of Cr, Ni, and Al, which in combination with the<br />cryogenic heat treatment RH950 at -50 °C gives the mechanical and chemical properties that meet the<br />requirements for steel with standard chemical composition.</p>

Achieving low hot tearing susceptibility in high-strength cast Al–Li alloys: Experimental investigation and simulation assessment

Due to the exceptional low density and high stiffness, cast Al–Li alloys are deemed suitable for structural applications. However, their economic benefits are limited by intolerable hot tearing susceptibility (HTS) during casting. This work aims to optimize alloy compositions that compromise low HTS and good mechanical properties. Six alloys (Alloys 1–6) with potentially high hot tearing resistance were selected by regulating Li, Cu and Mg additions based on the Kou's criterion and ProCAST simulation. Experimental results indicated that in contrast to Alloys 1–4, Alloys 5 & 6 containing higher solute contents show anomalously high HTS, significantly deviating from the predictions. It was further revealed that this phenomenon originates from a variety of Li-rich inclusions formed at interdendritic channels, which lead to strain localization and hinder residual liquid refilling. Then, Alloys 1–4 with low HTS were subjected to a tailored subsequent heat treatment to achieve optimal mechanical properties. Among the tested alloys, Alloys 3 & 4 exhibit comparatively lower ductility attributed to strain accumulation at the interface between coalesced Sʹ-Al2CuMg phases and Al matrix. In comparison, a good combination of strength and ductility (YS = 371 ± 14 MPa, UTS = 456 ± 19 MPa, EL = 2.5 ± 0.1 %) was successfully achieved in Al-2.5Li–2Cu–1Mg-0.15Zr alloy (Alloy 2) due to the synergistic reinforcement of δʹ-Al3Li and T1-Al2CuLi precipitates. Compared to other available cast Al–Li alloys, Alloy 2 possesses better hot tearing resistance while being highly competitive in strength. Our results are anticipated to contribute scientific guidance for developing high-performance cast Al–Li alloys with low HTS.

Effects of post-deposition annealing on structure and mechanical properties of multilayer Ti/DLC films

The multilayer (Ti/DLC) × 3 films were deposited using a DC arc evaporator with a titanium cathode and a pulsed cathode-spark evaporator with a graphite cathode. Following the deposition of the films, a heat treatment process was performed in air and Ar atmosphere at temperatures of 200 °C and 400 °C. The investigation of the films involved the examination of their structure, surface morphology, and chemical composition using AFM, SEM, XPS and Raman. Additionally, the mechanical properties of the films were assessed by nanoindentation, sclerometry and wear test. Changes in the structure, RMS roughness, С-sp2/С-sp3 ratio of carbon atoms in the film and the formation of Ti-C carbide were determined in relation to the heat treatment conditions. Studies have demonstrated that subjecting materials to heat treatment at temperatures of 400 °C results in a decrease in friction coefficient and an increase in hardness. The deposition of films on the working surfaces of microdrills with subsequent heat treatment leads to a reduction in wear, an extension of their service life, and an improvement in drilling accuracy as compared to microdrills without films. Furthermore, microdrills with (Ti/DLC) × 3 films annealed in air at 400 °C exhibit negligible size reduction and better drilling accuracy.

Atomic-scale compositional complexity ductilizes eutectic phase towards creep-resistant Al-Ce alloys with improved fracture toughness

Hierarchical microstructures spanning from micro-sized eutectic structure to nano-sized precipitates are promisingly engineered in lightweight Al alloys to improve the high-temperature creep resistance that is increasingly required for rapid industrial development. However, the intrinsically-brittle eutectic phase is ready to fracture upon applied loading, which, dramatically reducing room-temperature ductility and fracture toughness, greatly hampers practical applications of the creep-resistant Al alloys. Here, through the combination of Sc microalloying with sub-rapid solidification, we observe the ductilization of Al11Ce3 eutectic phase in cast heat-resistant Al-Ce-Sc alloys due to the formation of atomic-scale compositional complexity. High-concentration Sc atoms are frozen within the Al11Ce3 intermetallic phase by the sub-rapid solidification, which then assemble into unusual atomic-scale compositional dipoles with the Sc atoms enriched at one pole and the Al atoms at the opposite during subsequent heat treatment. The dispersed Sc-Al compositional dipoles induce local lattice distortions that stimulate dislocation activities, as temporally and spatially visualized by in-situ neutron diffraction tensile test and microstructural characterizations. The unexpected plastic deformation triggered in Al11Ce3 improves the deformation compatibility between the eutectic phases, enabling the sub-rapidly-solidified Al-Ce-Sc alloy to reach a room-temperature tensile elongation 3 times and fracture toughness over 8 times of its counterpart derived from traditional solidification. In addition, the sub-rapidly-solidified Al-Ce-Sc alloy exhibits an excellent creep resistance at 300 °C, achieving a tensile creep stress threshold of ∼ 70 MPa. These findings provide new perspectives on the design of ductile intermetallic phases and the development of creep-resistant Al alloys with application-level ductility.

Synthesis of Molybdenum Oxide Nanofibers with Multiple Surface Facets Via Electropsinning Followed by Rapid Thermal Treatment

A MoO3 nanofiber prepared by electrospinning and subsequent heat treatment is attracting significant attention due to its structural advantages. Vibrant studies are being conducted to control its morphology and diameter to improve its properties. In this study, we demonstrated the synthesis of α-MoO3 nanofibers with multiple surface facets by controlling the heating rate and temperature in the heat treatment step for removing polymer and crystallizing MoO3 from the electrospun polymer/precursor nanofibers. The analysis results show that the faster heating rate and higher heat treatment temperature in the thermal treatment process are more favorable for forming a shape in which particles with facet planes are connected. Finally, we observed the morphological change according to the heat treatment time to confirm the effect of the heat treatment conditions on the shape of MoO3 and interpreted the results in terms of nucleation and crystal growth.

Microstructural Evolution of Tantalum During Deformation and Subsequent Annealing

Microstructure-aware models are necessary to predict the behavior of material based on process knowledge or to extrapolate mechanical properties of materials to environmental conditions which are not easily reproduced in the laboratory, e.g., nuclear reactor environments. Elemental Ta provides a relatively simple BCC system in which to develop a microstructural understanding of deformation processes which can then be applied to more complicated BCC alloys. In situ neutron diffraction during compressive deformation and subsequent heat treatment have been used to monitor the evolution of microstructural features in Ta throughout simulated processing steps. Crystallographic texture and dislocation density are determined as a function of first plastic strain, then temperature. Lattice strains are determined and attributed to stresses at macroscopic, grain and dislocation length scales. The increase of the dislocation density through deformation and subsequent recovery during heat treatment is monitored through the changing diffraction line profile. Also, randomization of the texture is used as a signature of recrystallization. The recovery of dislocations through annihilation is not observed to depend on the initial dislocation density in the range studied here. In contrast, recrystallization is observed to depend strongly on the initially dislocation density.

A novel alloy design approach in developing CoNi-based high entropy superalloy using high entropy alloys thermodynamic and spark plasma sintering

This study introduces an innovative alloy design strategy by integrating HEAs principles to develop CoNi-based high entropy superalloys (HESAs). The powder of designed HESA produced using gas atomization and consolidated using spark plasma sintering (SPS). The alloy design strategy validated by CALPHAD to mitigate detrimental phase precipitation and segregation during powder production, material consolidation, and post-processing heat treatments. CoNi-HESA powder with a calculated mixing entropy of 1.568R was successfully developed and consolidated using SPS. Optimization of SPS parameters at 1175 °C, 10 min, and 100 °C/min achieved a relative density of 99.9 %. Subsequent heat treatments further improved the material's characteristics. Solutionizing at 1190 ± 10 °C for 2 h with water quenching resulted in a fine grain structure of ∼7 μm grain size. Aging at 900 °C for 24 h, followed by water quenching, yielded uniformly distributed fine γ′ precipitates comprising approximately 65 % of the γ matrix, without unwanted secondary precipitates or TCP phases. This study demonstrates the effectiveness of the novel approach in designing CoNi-based HESAs and optimizing their properties through careful process parameter selection and post-heat treatment cycles. The combination of thermodynamic calculations, HEA principles, and powder metallurgy techniques offers a promising approach for developing advanced high entropy superalloys with tailored microstructures.

Additive friction stir deposition of Al 6061-B4C composites: Process parameters, microstructure and property correlation

Al 6061-B4C metal matrix composites were fabricated using a novel solid state additive manufacturing technique of additive friction stir deposition (AFSD). Incorporation of B4C particles into the deposit was achieved by employing hollow Al 6061 feed stock filled with B4C powder and three different AFSD tool rotational speeds (200, 300 and 400 rpm). Fabricated deposits exhibited remarkable metallurgical bonding across the substrate/deposit interface and interlayer interfaces for all tool rotational speeds, indicating a wider fabrication window. A physics based pseudo-thermo mechanical model was employed to evaluate the thermo-kinetic conditions experienced by the depositing material to correlate with the microstructural observations. Deposited layers exhibited refinement of grains to ∼10 μm from the corresponding coarse grain structure of feedstock (136 μm). The regions near the B4C particles were observed to have finer grains (<2 μm) signifying particle stimulated nucleation. Although considerable loss in the tensile properties (60 % drop in yield strength) was observed in the AFSD deposits due to the associated dissolution of β’’ precipitates, subsequent heat treatment restored the tensile properties to the level of as received material (∼290 MPa). The thermo-kinetic conditions (temperature in excess of 500 °C and strain rates in excess of 250 s−1) experienced by the builds under higher AFSD tool rotational speeds (300 and 400 rpm) appeared to result in refinement of Al–Fe–Si based secondary intermetallic precipitates/dispersoids leading to the observed higher stability of their microstructure during the subsequent post AFSD heat treatment. Samples AFSD fabricated with a lower tool rotational speed of 200 rpm, however, exhibited significant grain growth on account of relatively larger secondary precipitates/dispersoids.

Practical surface-reconstruction strategy based on self-reactive interface design enables ultralong cyclability of commercial cathodes for lithium-ion batteries

Although Al-doped high-voltage LiCoO2 (HVLCO) cathode has been widely used in commercial lithium-ion batteries, it still suffers from poor cycling stability due to its unstable surface/interface structure causing bad side reactions. Herein, a surface reconstruction strategy based on self-reactive interface design has been proposed, to construct a uniform and ultrathin (∼ 5 nm) LiAlO2 (LAO) layer on the surface of HVLCO cathodes. The construction of LAO layer is realized by a facile and scalable process involving chemical immersion in LiOH solution and subsequent heating treatment. Moreover, the LAO coating layer imparts both lower interior stress upon lithiation and lower migration energy barrier of Li ions, guaranteeing stable and rapid lithium storage, which is confirmed by substantial characterizations and theory calculations. Consequently, ultralong cycle life over 10,000 h (1000 cycles) at 0.1 C is achieved for the surface-reconstructed HVLCO cathode, with an 86% capacity retention. Especially, different kinds of commercial HVLCO products as well as NCM (LiNi0.6Co0.2Mn0.2O2) cathode material, after the same surface reconstruction, also show remarkably reinforced electrochemical performance. This practical surface-reconstruction strategy may serve as a useful guideline for future design and performance optimization of commercial cathode materials.

Simultaneous enhancement of elevated temperature strength and ductility in additive-manufactured nickel-based superalloy via doping Y2O3 nanoparticles

In this work, we coated a layer of Y2O3 particles in Hastelloy X (HX) nickel-based superalloy powder by in situ chemical method and combined with laser powder bed fusion (LPBF) technology to develop a high-performance Y2O3-doping alloy, designated as Y-HX. The results show that the doping of Y2O3 particles prevents crack formation during the printing process and reduces solute segregation at cell and grain boundaries by increasing the viscosity of the molten pool. The doping of Y2O3 particles to the printed Y-HX alloy enhances grain boundary characteristics, transforming coarse sheet-like carbides into finely dispersed granular carbides at the boundaries during subsequent heat treatment. Additionally, doping with Y2O3 particles increases the recrystallization activation energy of the Y-HX alloy from 149.4 to 278.8 kJ mol–1. At 750 °C, the Y-HX alloy exhibits an ultimate tensile strength of 619 ± 2 MPa and an elongation of 52 % ± 2 %, along with an ultimate tensile strength of 325 ± 3 MPa and an elongation of 47 % ± 2 % at 900 °C. Our work provides a promising way to develop additive-manufactured superalloys with exceptional thermal stability and remarkable high-temperature mechanical properties.