Heat Treatment Conditions Research Articles

Revealing the γ′ and γ″ Phase Fractions of Additively Manufactured and Differently Heat‐Treated Nickel‐Base Superalloy IN718 by Atom Probe Tomography and Their Impact on Mechanical Properties

Powder bed fusion using a laser beam (PBF‐LB) has great potential for the production of geometrically complex industrial components, allowing for unprecedented geometrical optimization and freedom of design. This potential is particularly relevant in the case of turbine components, whose microstructure and properties are directly affected by the extreme PBF‐LB processing conditions. In this context, this study aims to investigate the impact of PBF‐LB on the microstructure and mechanical behavior of Inconel alloy 718 (IN718) when heat treated according to different sequences. Atom probe tomography is used to analyze the composition, morphology, configuration, and volume fraction of γ′ and γ″ precipitates as a function of heat treatment conditions. Their impact on the material is evaluated using compression tests under different build orientations. It is shown that when PBF‐LB IN718 is subject to solution annealing at 930 °C and subsequently aged, δ needles form in its microstructure at the expense of γ′ and γ″, thus reducing mechanical strength. Such is not the case when the solution annealing step is omitted or when its temperature is increased to 1000 °C, conditions whose superior mechanical behavior have been attributed to a high dislocation density and a large volume fraction of aging phases, respectively.

Synthesis of Ce-Based RE2Fe14B by Solid-State Reaction and Reduction-Diffusion Process

Rare-earth permanent magnets, such as Nd2Fe14B, have been widely used in electric vehicle and wind turbine motors due to their high anisotropy field (Ha), saturation magnetization (Ms) and coercivity (Hc). Cerium (Ce) has gained attention as a potential alternative to neodymium (Nd) due to its high abundance and low cost. The relatively poor intrinsic magnetic properties of Ce magnets, however, remain a significant challenge for their industrial applications. In this study, the synthesis of Ce-based RE2Fe14B (2-14-1) phases was achieved by a modified reduction-diffusion (R-D) process using REFeO3 (RE = Ce, Nd) as a precursor. The precursor was prepared by a solid-state reaction with CeO2, Nd2O3, Fe2O₃ and Fe powders, which is a much more suitable process for mass production and cost-effectiveness. Optimal composition and heat treatment conditions enabled the formation of single-phase Ce-based 2-14-1 particles. The as-synthesized single-phase Ce2Fe14B particles exhibited an Ms value of ~120 emu/g and an intrinsic coercivity (Hci) value of ~85 Oe, which can be attributed to the large particle size as observed by FE-SEM.

Fabrication of stable hydrogel microspheres with hydrophobic shell using water-in-water (W/W) Pickering emulsion template

Hydrogel microspheres are promising for food applications. The water-in-oil (W/O) emulsion template is commonly used to prepare the hydrogel microspheres. However, this method often involves synthetic surfactants and toxic organic solvents to remove the oil phase. The swelling problem of the resultant microspheres is another obstacle. In this study the water-in-water (W/W) emulsion template of gelatin-in-dextran was used to prepare the hydrogel microspheres, without the addition of surfactants, toxic reagents and high energy input. To prevent swelling, zein particles modified with alginate were served as a hydrophobic shell of the gelatin core. The formation evolution of these core–shell microspheres and its relevant factors including phase behavior of the immiscible gelatin/dextran, the binding of zein/alginate and the addition of the modified zein particles were investigated. It was found that small amount of alginate could induce zein particles to absorb on the gelatin surface, whereas the excess led to absorption competition. When using 0.6 wt% particles with zein/alginate ratio of 1:0.5, the ideal core–shell microspheres which were fully covered by the particles and with a self-supporting architecture in uniform size (18.8 ± 0.1 μm) and spherical shape were obtained. These microspheres showed remarkable stability under the conditions of heat treatment, varied pHs and salt concentrations and long-term storage either in refrigerator or room environment. Their sizes were easily manipulated by adjusting the concentration and molar mass of the biopolymers. It is believed that the desired stability and tunable sizes of these edible core–shell microspheres could contribute the development of their applications in foods.

Synthesis and lubrication properties of hollow IF-MoS2 nanospheres

Hollow IF-MoS2 nanospheres were prepared by sulfidation reaction using MoO3 nanospheres as precursors in a reducing atmosphere. The composition and morphology of the obtained samples were characterized by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The formation mechanism was further studied. The results showed that smaller sized MoO3 nanospheres (synthesized from 0.05 mol of ammonium molybdate) could transform into hollow IF-MoS2 nanospheres under heat treatment conditions at 850 °C for 6 h. Furthermore, we evaluated the lubrication performance of hollow IF-MoS2 nanospheres. Comparative analysis with pure oil revealed that the mixed oil, with the addition of 2 wt. % IF-MoS2, exhibited a reduced friction coefficient ranging from 0.0194 to 0.0197.

Heat treatment effects on the shear performance and microstructure evolution of W-core SiC fibers

SiC fiber reinforced titanium alloy matrix composites employed in elevated temperature aeroengine components are subjected to complex loading conditions. Investigating the shear performance of SiC fibers after heat treatment can help ensure the load-carrying capability of composites at service temperatures. This study presents a novel double shear testing method for W-core SiC fibers. The shear strength and stiffness of the SiC fibers in as-received and heat-treated conditions were measured. The morphologies of SiC fibers’ shear fracture surfaces and C coatings were thoroughly analyzed. The evolution of the internal microstructure and the composition of reaction layers after heat treatments were investigated. The shear strength of W-core SiC fibers at 95% survival probability reached 588.64MPa after 200 h of heat treatment at 600°Celsius, representing a 55% improvement over both the as-received and 1100°Celsius heat-treated conditions. After heat treatment at 1100°Celsius, the reaction layer between the W core and the SiC sheath thickened exponentially due to extensive elemental diffusion, resulting in the formation of numerous Kirkendall voids. The voids facilitated crack initiation and propagation, leading to a deterioration in fiber shear performance. The insights gained in this study regarding the shear properties of SiC fibers can provide support for predicting the mechanical performance of composites under complex loading conditions.

Enhancing high-performance concrete with local andesite and calcined marl: Insights from heat treatment and untreated conditions

This study explores the incorporation of local Algerian andesite and calcined marl as supplementary cementitious materials in high-performance concrete (HPC), with a special focus on the effects of heat treatment. Advanced analytical techniques, including X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), were used for material characterization. The Sherbrooke method was utilized for mix design optimization, and thermal curing effects were critically evaluated. Key results demonstrated that both andesite and calcined marl significantly enhance HPC performance. Fresh mixtures showed excellent workability and consistent density. In the hardened state, these admixtures reduced porosity and water absorption capacity, improving durability. Heat-treated samples exhibited substantial early strength gains, while non-heat-treated samples showed superior long-term strength due to ongoing pozzolanic activity. Ultrasonic pulse velocity (UPV) measurements confirmed the high quality of the concrete. Tomography revealed a dense pore structure and strong interfacial transition zones, contributing to overall performance. Statistical modeling using the Design of Experiments (DOE) methodology validated the experimental findings and identified optimal conditions for maximizing compressive strength. Sulfuric acid exposure tests indicated good chemical resistance, with balanced performance in maintaining residual strengths and managing weight losses. This research underscores the potential of using local andesite and calcined marl to enhance HPC, promoting sustainable construction practices in Algeria by reducing reliance on imports and utilizing regional resources. In summary, this study contributes to sustainable HPC development by demonstrating the effectiveness of local mineral admixtures. The dual benefits of heat treatment for early strength gain and non-heat-treated conditions for long-term durability offer valuable insights for optimizing HPC formulations, advancing our understanding of pozzolanic materials, and promoting environmental stewardship and economic efficiency in the construction industry.

Grey Relationship Analysis of Cutting Forces and Surface Roughness in Turning using Cryo-treated and Untreated Cutting Tools

The aim of this experimental study is to establish the optimum heat treatment procedure and machining parameters to obtain values of cutting force and surface roughness in machining AISI 1050 workpiece by utilizing grey relations analysis based on Taguchi method. In this regard, machining operations were carried out at three different cutting speeds and three different feed rates at a constant depth of cut. Taguchi mixed-level design L18 (2^2 3^2) was chosen for machining experiments. The optimum heat treatment and machining parameters for determination of cutting force and surface roughness values were identified according to the fact that higher the Signal/Noise ratio is better based on grey relations analysis of Taguchi method. The results showed that the optimum parameters for surface roughness and cutting forces were obtained as 0.1 mm/rev at feed rate and 180 m/min at cutting speed with cryo-treated cutting tool. According to ANOVA table and Signal/Noise ratios, it was specified that the most effective parameters on cutting forces and surface roughness were feed rate, cutting speed and heat treatment conditions, respectively.

Influence of quenching and tempering heat treatment on heat flux to the workpiece in dry milling of AISI 1045 steel

Dry machining offers cost and environmental benefits in metal cutting, but the absence of cutting fluid can elevate workpiece temperature, impacting surface quality and dimensional accuracy. This study explores and quantifies the impact of quenching and tempering heat treatment on the heat flux to the work material in dry milling AISI 1045 steel. Inverse heat transfer analysis determines the maximum magnitude of a moving Gaussian heat source corresponding to the heat load into the milled part. The inverse estimates are obtained from temperature measurements taken when machining samples subject to different heat treatment conditions. The estimated heat flux and the measured temperature are discussed in the context of the metallo-thermomechanical connection with microstructural aspects, hardness, and thermal properties. The results reveal a substantial increase in thermal energy transferred to the milled steel when quenched and tempered, with a 33 % higher heat input compared to normalized conditions. This condition is mainly attributed to the increased hardness and reduced thermal conductivity of the tempered martensitic structure obtained through hardening. The estimates show deviations of less than ±5 %, according to uncertainty calculations based on thermal sensitivity and sensor accuracy.

Microstructure evaluation of Si-modified aluminide coatings on IN625 deposited by slurry aluminizing process

Si-modified aluminide coatings are promising for improving oxidation and corrosion resistance in superalloys at high temperatures. This study investigated the effect of different silicon levels in the aluminizing slurry on the morphology and structure of Si-modified aluminide coatings on IN625. This process involved spraying a slurry of aluminum and silicon particles in an aqueous PVA solution onto IN625 samples, followed by heat treatment under controlled conditions - two atmospheres (air and argon) and two heating ramps (regular and flash). Surface morphologies, cross-sectional structures, elemental compositions, and phase formations were analyzed using FE-SEM, SEM, EDS, and XRD methods, while DTA analysis assessed AlSi alloy formation during heating. The results showed that higher silicon content in the slurry increased silicon incorporation in the coatings but did not reduce aluminum activity enough to deposit a low-activity aluminide coating. The inert atmosphere (argon) and flash heating promoted the co-deposition of Si and Al, resulting in Cr and Mo silicide-enriched outer layers in some samples. The aluminum content in all slurries was sufficient for consistent β-NiAl formation across different silicon levels. The average silicon content in coatings ranged from 5 to 15 wt% and depended on the slurry composition and heat treatment conditions. The Al30Si slurry produced the thickest coatings (~90 μm), with further increases in Si leading to reduced thickness. This study suggests that slurry aluminizing can be optimized to control silicon incorporation, depositing Si-modified aluminide coatings for durable, high-performance applications.

Investigation of microstructure, mechanical performance, and corrosion resistance of thin-walled titanium welded pipe by annealing process

Thin-wall titanium welded pipe has important applications in the fields of new energy vehicles, aerospace, and heat exchangers, the mechanical properties and corrosion resistance after high-frequency induction welding are rarely studied. To improve the comprehensive performance of thin-walled titanium welded pipe, a heat process and the performance optimization mechanism were studied in this paper. In addition, we systematically explored the influence of heat treatment conditions on the microstructure, mechanical performance, and dissolution behavior of the welded pipe through various methods, including tensile tests, immersion tests, and electrochemical tests. The results indicated that heat treatment primarily regulates the quantity and distribution of martensitic phases, acicular structures, and serrated structures in the welded joints, thereby impacting the mechanical performance of the welded pipe. By following high-temperature annealing at 800 °C for 0.5 h, with a heating rate of 5 °C/min, the acicular and serrated structures in the welded joints completely disappeared, forming an annealed equiaxed structure consistent with the base material. Subsequent furnace cooling reduced internal thermal stresses within the grains, resulting in relatively smooth grain boundaries, reduced small-sized grains, and a more uniform distribution of grain sizes, ultimately eliminating the residual stresses. Consequently, the welded pipe exhibited outstanding comprehensive performance, including ultimate tensile strength, Vickers hardness, and fracture elongation of 439.2 MPa, 178.3 HV, and 18 %, respectively. Notably, under room temperature, after immersion in a 3.5 % sodium chloride solution for 28 days, there was no significant change in the sample's mass. Therefore, the properties of thin-walled titanium welded pipe can be improved by annealing process, and it provides strong support and reliable evidence for its application in related fields.

RESEARCH OF PHASE FORMATION IN TRANSPARENT GLASS-CERAMIC PROTECTIVE COATINGS FOR CERAMOGRANITE

The perspective of the development and introduction of porcelain stoneware by domestic producers using natural raw materials from the subsoil of Ukraine for the needs of the raw material and fuel-energy complex in the conditions of military operations has been established. The need to create new types of ceramic granite was determined, taking into account new approaches, regarding the use of alternative raw materials and modern technological principles of creating nanostructured glass materials. The purpose and tasks of the work are formulated, which determine the need to study the structure and phase composition of porcelain stoneware under the conditions of high-speed heat treatment. A hypothesis has been formulated regarding the production of transparent wear-resistant protective coatings based on high-calcium alkaline aluminosilicate frits, which consists in the possibility of forming a strengthened optically transparent sytalized glass structure with a high-speed heat treatment mode and the flow of surface crystallization to ensure a wear-resistant structure of the 4th degree. The processes of phase formation that take place during the heat treatment of the base frit and the protective coating for porcelain stoneware have been studied and the priority role of the metastable phase separation of glass in the formation of the sytalized structure has been determined. It was established that the formation of crystallization nuclei by means of metastable phase separation allows for the formation of a sytalized structure of the protective coating for ceramic granite with the content of crystalline phases of anorthite with a size smaller than the wavelength in the visible part of the spectrum and α-corundum in the near-surface layers of the glaze, which simultaneously ensures optical transparency and wear resistance of the developed coating. Transparent glass-ceramic coatings with high operational properties, developed and implemented in the production conditions of PrJSC «KhPZ», will significantly increase the competitiveness of domestic ceramic tiles and contribute to the stabilization of the market in the conditions of sustainable development of the state.

Improved piezo-photocatalytic activity by controlling the oxygen vacancy content of NaNbO3 powders

The sintering temperature of solid-state synthesis exceeds 1000 °C, which easily leads to the formation of oxygen vacancies. The presence of oxygen vacancies can alter the electronic/crystal structure and surface chemical properties of perovskite oxides. In this work, the content of oxygen vacancy of NaNbO3 are controlled by adjusting the heat treatment conditions including atmosphere, temperature, and time. XPS and EPR are used to analyze the relative content of oxygen vacancies. The N2 heat treatment time is 3 h, and as the temperature increases from 300 °C to 900 °C, the oxygen vacancy content increases from 16.4 % to 18.9 %. At 900 °C, the time is extended to 5 h, and the oxygen vacancy content increased to 26.4 %. The disordered outer structure in HRTEM images confirms the existence of oxygen vacancies. The effect of the presence of oxygen vacancy on the efficiency of piezocatalysis and piezo-photocatalysis of NaNbO3 is cleared. The NaNbO3 sample heat-treated in N2 for 3 h (named NN-3h N2) showed the best piezo-photocatalytic performance, with a rate constant (k) of 0.19175 min−1, which is much higher than the unmodified NaNbO3 (0.11777 min−1). The electrochemical test results show that the NN-3h N2 sample has better charge transfer ability and stronger photocurrent response, indicating that the presence of oxygen vacancies improves the migration and transfer efficiency of charge carriers. The volcanic trend indicates that an appropriate oxygen vacancy content is beneficial to the improvement of piezo-photocatalytic performance.

Tribological performance of 410L martensitic stainless steel parts manufactured by Laser directed energy deposition

The processing of AISI 410L martensitic stainless steel (MSS) by laser directed energy deposition (L-DED) for additive manufacturing (AM) of wear-resistant components is an alternative to the high C-content MSS grade, with difficult processability. This work assesses the tribological performance of low C-content 410L MSS additively manufactured by L-DED. Two sets of L-DED parameters were investigated, one targeting Production and high deposition rates, and the other for Resolution and increased geometric freedom. Half of the multilayer samples were subjected to a post heat-treatment route. Samples were evaluated by the dry-sliding linearly reciprocating ball-on-flat tribological test (ASTM G133) in the as-built and heat-treated states. Commercially annealed 410 MSS was the reference material. In the L-DED as-built, microstructures were composed of ferrite with martensite at the grain boundaries. Heat-treatment provides recrystallization, martensite tempering, and hardness decrease. The more refined microstructure of L-DED resolution as-built led to greater hardness and lower wear coefficient in the ASTM G133 test. Wear tracks revealed wider bands of compact tribolayers on its surface, which reduced the action of adhesive and abrasive mechanisms. The other L-DED as-built and heat-treated conditions, and 410 reference material demonstrated a large amount of free debris, indicating lower wear resistance.

THE EFFECT OF HEAT-TREATMENT ON THE MECHANICAL PROPERTIES OF EXPANDED GLASS PARTICLE/A356 SYNTACTIC FOAM

This research investigates the manufacturing of metal syntactic foams (MSFs) using a packed bed of porous (2-2.8 mm) expanded glass (EG) within an A356 alloy matrix. To this end, the counter-gravity infiltration casting technique is employed to manufacture the specimens. The density of the MSFs ranges from 1.05 to 1.17 g/cm3, making it one of the lowest densities foams, attributed to the filler particles' low bulk density. The study investigates the influence of T6 heat treatment on the mechanical properties and microstructural characteristics of the manufactured MSFs. The mechanical properties of the MSFs are characterized under quasi-static compressive loads at 1 mm/min. After heat treatment, the compression test results indicate a significant enhancement in most mechanical properties. Compression strength and plateau stress are approximately doubled compared to as-cast foams for samples with similar densities. While energy absorption of the MSFs triples in heat-treated conditions. These improvements are attributed to changes in the matrix microstructure due to thermal treatment. Microstructural analysis reveals that Si particles, initially sharp and continuous within inter-dendritic boundaries, become blurry and discontinuous through spheroidization after thermal treatment. This hinders crack growth in the cell wall and mitigates the effects of casting defects and the columnar dendritic structure. The majority of mechanical properties in both heat-treated (HT) and as-cast (AC) foams exhibited an increase in density due to an increase in the matrix fraction. However, plateau end strain and energy absorption efficiency demonstrated an independent effect of heat treatment and density.

3D printing austenitic stainless steel 316L by cold spray process: optimum post-spraying heat treatment conditions

3D printing austenitic stainless steel 316L by cold spray process: optimum post-spraying heat treatment conditions

Peptidomic Analysis of Potential Bioactive Peptides in Mare Milk Under Different Heat Treatment Conditions.

Active peptides in mare milk have unique biological activities, but how the bioactive protein in mare's milk changes under the influence of temperature has not been fully studied. Therefore, in this study, the differential expression of bioactive peptides potentially present in horse milk under different heat treatment conditions was investigated for the first time using peptidomic and bioinformatic techniques. We collected a total of 15 samples. In this study, we divided the samples into five groups, specifically, 65 °C, 30 min; 72 °C, 15 min; 83 °C; 10 min; 95 °C, 5 min; and an untreated group as a control, which involved four different temperature treatments, in order to understand changes in bioactive peptides and to identify the sequence of bioactive peptides. In the experiment, a total of 2341 active peptides were identified. The amino acid composition of the potential active peptides remained stable across different temperatures, but their abundance varied with temperature. In all, 23 peptides from 20 different proteins were identified, with the highest number of active peptides identified at 72 °C. Through database searches, we found that a majority of these peptides were within β-lactoglobulin and immunoglobulin domain proteins, which are known for their potential biological activities. These findings provide a theoretical foundation for the development of peptides with different bioactivities as potential functional foods.

Unexpected thermal aging effect on brittle fracture and elemental segregation in modern dissimilar metal weld

A full-scale dissimilar metal weld safe-end mock-up, precisely replicating a critical component of a modern nuclear power plant, was investigated. The brittle fracture behavior, carbide evolution and nanoscale elemental segregation in the heat-affected zone (HAZ) of low alloy steel (LAS) were analyzed under both post-weld heat-treated and thermally-aged conditions (400 °C for 15,000 h, equivalent to 90 years of operation) using analytical electron microscopy and atom probe tomography. The observed increase in grain boundary (GB) decohesion and intergranular cracking on the fracture surface and the decrease of fracture toughness are primarily attributed to P and Mn segregation to GBs and the coarsening of carbides upon long-term thermal aging. The direct observations of significant elemental segregation to GBs and the consequent reduction in fracture toughness in the HAZ are unexpected for modern low-phosphorus LASs, highlighting potential concerns for evaluating the structural integrity of modern nuclear power plants.

Preparation and scintillation properties of Eu3+-doped high crystallinity tellurite glass ceramics

In this study, a high-crystallinity glass-ceramic scintillator doped with Eu³⁺ containing Bi₂Te₄O₁₁ nanocrystals was prepared using a traditional melt crystallization method. The optimal heat treatment conditions, phase structure, and luminescent properties of the glass-ceramics were systematically investigated using various characterization techniques, including DSC, XRD, SEM, and spectrophotometry. To achieve glass-ceramic samples with high transmittance and excellent luminescent performance, the optimal heat treatment process was determined to be 500 °C for 10 min. The final sample was found to have a density of 5.9 g/cm³ and a crystallinity of 70 %. Strong orange-red light emission was exhibited by the glass-ceramic under both 465 nm light and X-ray excitation. The maximum integral X-ray excited luminescence (XEL) intensity was found to reach 20.2 % of that of the commercial Bi4Ge3O12 (BGO) scintillation crystal. It is indicated by the research that Eu³⁺-doped high-crystallinity tellurate glass-ceramics are promising candidate materials for scintillators in the field of X-ray detection.

Tensile Strength Property with PdCo-Cu Multi-Layer Lamination and Heat Treatment of MEMS Probe for Probe Card

Cantilever wire probe card has limited to transport high-speed signal because of long wire but it is suitable for inspecting high-current and high voltage semiconductor such as wide band gap (WBG) power semiconductors.Superior mechanical property of a probe card wire is in demand because it is respectively used wafer inspection with in and out pad on the top surface of the power semiconductor wafer. Therefore, in this study, tensile specimens of micro electro-mechanical systems (MEMS) probe alternatively layered and electroplated with palladium (Pd)-cobalt (Co) alloy layers and copper (Cu) layers. MEMS probe was also measured tensile strength and elongation with multi-lamination and heat treatment conditions. Additionally, fractography of fracture surface after tensile test were analyzed using a scanning electron microscope (SEM). As the number of PdCo-Cu multi-layer increased, 11, 15 and 21 layered specimens showed higher tensile strength and longer elongation than 5 layered specimens because of the increase of laminated interface of PdCo and Cu. 7 layered specimen after isothermal aging had higher tensile strength and longer elongation than before isothermal aging. In 5, 11, 15 and 21 layered specimens, the fracture surfaces of tensile test specimens without aging treatment showed a ductile-brittle mixed fracture mode. Fracture surfaces of 7-layered specimen before and after isothermal aging showed a ductile-brittle mixed fracture mode.

Feasibility Study of Solid-State Recycling through Direct Hot Rolling of AA5754 Aluminum Chips for Automotive Applications

Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.