Heat Treatment Regimens Research Articles

Regulating the partially mixed zone via post-weld heat treatment to enhance sulfide stress corrosion cracking resistance of the Inconel 625/X80 weld overlay

This paper investigated the effect of post-weld heat treatment (PWHT) on microstructure evolution and sulfide stress corrosion cracking (SSCC) behavior of the fusion boundary (FB) region of Inconel 625/X80 weld overlay, with a focus on the partially mixed zone (PMZ). Three heat treatment regimens were designed, namely 620 °C/10 h, 620 °C/20 h, and 670 °C/10 h, in which 620 °C/20 h was proved to be the optimal parameter. The 10-hour PWHT conditions might induce heterogeneous carbon distribution owing to insufficient tempering duration, exacerbating the hardness mismatch in the FB region and thus promoting the development of SSCC. Following the 620 °C/20 h treatment, most of the brittle phase with high hardness in the FB region was eliminated, reducing the nucleation site for SSCC. More importantly, martensite in the PMZ was transformed into austenite with rod morphology, while cementite adjacent to the PMZ might evolve into dispersed refined austenite. Austenite shows low hydrogen sensitivity, enhancing the SSCC resistance of the PMZ. On the other hand, the carbides in the X80 matrix might restrict the diffusion of hydrogen toward the PMZ, thereby reducing the susceptibility of the PMZ to SSCC.

Data-Driven Design of Nickel-Free Superelastic Titanium Alloys.

In this paper, a CatBoost model for predicting superelastic strains of alloys was established by utilizing features construction and selection as well as model filtering and evaluation based on 125 existing data points of superelastic titanium alloys. The alloy compositions of a TiNbMoZrSnTa system were optimized and three nickel-free titanium alloys with potentially excellent superelastic properties were designed using the Bayesian optimization algorithm using a superelastic strain as the optimization target. The experimental results indicated that only Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn exhibited clear superelasticity due to the absence of relevant information about the alloys' β stability in the machine learning model. Through experimental optimization of the heat treatment regimens, Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn ultimately achieved recovery strains of 4.65% after being heat treated at 853 K for 10 min and 3.01% after being heat treated at 1073 K for 30 min, respectively. The CatBoost model in this paper possessed a certain ability to design nickel-free superelastic titanium alloys but it was still necessary to combine it with existing knowledge of material theory for effective utilization.

Study on Microstructure and Properties of Additive-Manufactured TC4ELI+TC21 Titanium Alloy Gradient Composite Structures

TC4ELI+TC21 titanium gradient composite structures with direct transition (TD1) and cross transition (TD2) were prepared using laser deposition manufacturing technology. The microstructure of the gradient interface was observed, and the distribution of alloying elements was detected. The tensile properties of the two alloys at room temperature were tested, and the effects of different heat treatment regimens on the microstructure and mechanical properties were investigated. The results show that there is no obvious defect at the gradient interface of the two alloys. Compared with direct transition alloys, the alloying elements of TD2 alloys change less at the interface, the structure of the transition zone is more closely bound, and the elongation is higher. After heat treatment, the α phase in the alloy is coarsened, and the alloy elements at the interface are fully diffused, so that the gradient interface of the alloy is eliminated to a certain extent, the tensile strength of the alloy decreases, and elongation increases. The strength and plasticity of the alloy reached their best match at a solution temperature of 930 °C.

Effect of Cold Deformation and Heat Treatment on the Microstructures and Mechanical Properties of Au-15Ag-12Cu-6Ni Alloy Sheets.

The evolution of the microstructure and hardness changes in the Au-15Ag-12Cu-6Ni alloy during the processes of cold rolling and annealing were investigated and the heat treatment regimen for the alloy was optimized in this article. The hardness of the alloy continuously increases with the cold rolling reductions, leading to continuous deformation of the grains during the cold rolling process, ultimately resulting in smaller grain sizes. Subsequent annealing induces recovery and recrystallization, achieving complete recrystallization at 700 °C. An intriguing softening effect is observed after annealing at 700 °C, manifesting in a significant reduction in hardness to 238 (Hv0.5). The cold deformation texture of the alloy aligns with the recrystallization texture type, exhibiting only a certain degree of angular deviation. This is primarily characterized by <111>//RD texture and a texture deviating 60° from RD towards TD. The performance of the finished sheet improves with the precipitation of ordered phases AuCu after a 300 °C heat treatment for 0.5 h, resulting in a remarkable hardness of 380 (Hv0.5).

Thermodynamic databases of Ti-Al-Fe-V quaternary alloy systems and its application

Pandat software based on Calculations of phase diagram (CALPHAD) was used in this study. Six binary systems and four ternary systems in the Ti-Al-Fe-V system were evaluated, compared, and optimized. A thermodynamic database of Ti-Al-Fe-V titanium alloys was established by selecting the most recent, accurate, and self-consistent thermodynamic parameters. The database was used to simulate the organization of equilibrium solidification and non-equilibrium solidification alloys of Ti-10V-2Fe-3Al, Ti-10V-3Al-1Fe and Ti-10V-3Al. The precipitated phase fractions of Ti-10V-2Fe-3Al at different temperatures were calculated using the database. The effect of different Fe contents and aging temperatures on the phase composition of the Ti-10V-2Fe-3Al alloy is given in conjunction with the calculated results. There is good agreement with the experimental results for the heat treatment regimens given by the calculations. The above results show that thermodynamic calculations based on phase diagrams can guide the formulation of process parameters for alloy casting and heat treatment. The established thermodynamic database for Ti-Al-Fe-V titanium alloys is accurate and reliable.

The effect of aging heat treatment on the formability and microstructure of the AA6063 tube in the rotary draw bending process

This research delves into the impact of aging heat treatment on both the formability and microstructural characteristics of 6063 aluminum tubes when subjected to the rotary draw bending (RDB) procedure. To ascertain a heat treatment regimen that can yield desirable hardness and formability for the bending process, the tube was subjected to T3, T6, and annealing heat treatment cycles under diverse conditions and subsequently the tube's bendability was evaluated. The findings indicate that as temperature and dissolution time are raised, there is a corresponding rise in the extent of elliptical deformation, consequently resulting in higher hardness values. The research outcomes suggest that elevating both temperature and dissolution time leads to a more pronounced elliptical shape in the bent sample. For instance, when subjected to heat treatment at 530 °C and 545 °C for 60 min, the samples exhibited respective increases in ellipticity of 5.30 % and 4.34 % compared to those treated for just 30 min. Additionally, higher internal pressure led to a reduction in the degree of elliptical deformation, notably a decrease of 9.85 % observed at a pressure of 20 bar. Moreover, the hardness of samples subjected to the T3 cycle exhibited an upward trend with increasing both temperature and duration of heat treatment. To elaborate, the hardness measurements were conducted at three distinct temperatures (530 °C, 545 °C, and 560 °C) and four different durations (30, 45, 60, and 75 min). The sample subjected to a 75-minute heat treatment at 560 °C exhibited the highest recorded hardness value, measuring at 62.55 HV. In summary, the results indicate that aging heat treatment can enhance the formability of 6063 aluminum tubes during the RDB process. Furthermore, it is noteworthy that temperature and internal pressure serve as crucial parameters to control in order to mitigate elliptical deformation and enhance hardness.

Effect of electromagnetic forming–heat treatment process on mechanical and corrosion properties of 2024 aluminum alloy

The 2024 aluminum alloys are used in a wide range of industrial applications, and improvement in their formability and serviceability is key in the manufacturing process. Electromagnetic forming (EMF) has proven to be an effective means of improving the formability of aluminum alloys. By combining EMF and heat treatment process, three samples of 2024 aluminum alloy were designed: Sample A (annealing + EMF + solid-solution + aging), Sample B (solid solution + EMF + aging), and Sample C (solid solution + pre-aging + EMF + aging). The effects of three heat treatment regimens on the properties and microstructure of 2024 aluminum alloy were studied by hardness test, intercrystalline corrosion, and exfoliation corrosion, as well as by microscopic characterization techniques including scanning electron microscopy and transmission electron microscopy. The results show that the dislocations-induced deformation could shorten the time to peak aging and led to the increase in peak strength. Sample C exhibited the highest strength and sample A exhibited the highest elongation and corrosion resistance. The microscopic results show that the differences in properties were mainly influenced by the distribution of precipitated phases and the width of the precipitation-free zone. The discrete and coarse grain boundary precipitations make sample A have excellent corrosion resistance. The fine and dense precipitated phases provide good strength for samples B and C, but also reduces the elongation. This research has important implications for rational formulation based on the combination of EMF and heat treatment processes for the fabrication of Al–Cu–Mg alloys. Conclusionsmay be made more concise. They should focus on the mechanisms responsible for high strength or corrosion resistance rather than the values obtained that are shown in results.

INFLUENCE OF HEAT TREATMENT ON MECHANICAL PROPERTIES OF WELDED JOINTS OF AW 2099 ALLOY

The paper is focused on the determination of the heat treatment effect on AW2099 welded joints properties. Laser beam welding was applied at constant welding parameters during the experiment. After the welding, solution annealing and artificial aging were applied at 150°C and 180°C for 24 hours. Subsequently, a static tensile test and microhardness measurement of welded joints were performed. The results of the tensile test showed that both heat treatment regimens resulted in an increase in the strength of welded joints and ensured an increase in hardness also in the area of the weld metal. The highest strength value (427.25MPa) was observed at a curing temperature of 150°C and a time of 24h.

Influence of Heat Treatment of Steel AISI316L Produced by the Selective Laser Melting Method on the Properties of Welded Joint.

This work is focused on the influence of heat treatment of a part produced by the SLM (selective laser melting) method of stainless steel, 316L. Two heat treatment regimens were tested and compared with the state without heat treatment. Subsequently, TIG (tungsten inert gas) welds were created on the base materials processed in this way. All welds were subjected to mechanical tests and microstructural analysis. The tensile test was performed both for the welded joint and for the base material in the transverse and longitudinal directions. The tensile strength values of the samples with the welded joint were compared with the values required for the base material, 316L forged steel (1.4404). Microstructural analysis revealed significant differences between samples with and without heat treatment. The results of these tests are supported by SEM analysis. EDAX (energy dispersive analysis of X-rays) semiquantitative analysis confirmed the presence of ultra-fine pores in the structure. The results of mechanical tests show that the solution annealing at 1040 °C for 0.5 h gives better results than the same heat treatment with a duration of 2 h.

Effect of Heat Treatment on the Mechanical and Corrosion Properties of Mg-Zn-Ga Biodegradable Mg Alloys.

Mg alloys have mechanical properties similar to those of human bones, and have been studied extensively because of their potential use in biodegradable medical implants. In this study, the influence of different heat treatment regimens on the microstructure and mechanical and corrosion properties of biodegradable Mg–Zn–Ga alloys was investigated, because Ga is effective in the treatment of disorders associated with accelerated bone loss. Solid–solution heat treatment (SSHT) enhanced the mechanical properties of these alloys, and a low corrosion rate in Hanks’ solution was achieved because of the decrease in the cathodic-phase content after SSHT. Thus, the Mg–4 wt.% Zn–4 wt.% Ga–0.5 wt.% Y alloy after 18 h of SSHT at 350 °C (ultimate tensile strength: 207 MPa; yield strength: 97 MPa; elongation at fracture: 7.5%; corrosion rate: 0.27 mm/year) was recommended for low-loaded orthopedic implants.

Investigations Towards Ultra-Low Cost Nb3Sn SRF Cavity Fabrication Via Melt Casted Bronze Route Processing

A novel approach to fabricating Nb3Sn SRF cavities and other RF components using an ultra-low-cost melt casting fabrication process has been investigated. This simple, low cost melt casting technique has the potential to be used to fabricate nearly any superconducting Nb3Sn structure using either the Bronze Route (BR), Internal Tin (IT), External Tin (ET) processes as well as normal conducting pure copper (Cu) cavities. Most of the heat treated samples that were examined using SEM/EDX seemed to show a reasonable correlation of Tc onset and transition width (ΔTc) of the ingots initial/starting Sn content to the desired stoichiometric Nb3Sn phase, where the lower starting Sn content coupons resulted in lower Tc's with broader transition widths and the higher starting Sn coupons resulted in higher Tc's with narrower ΔTc's. The best samples had Tc onsets ∼17–18 K and ΔTc's < 2 K. Two samples were further tested for RF surface resistance (Rs) and Quality Factor (Q) at JLAB. These RF measurements were performed at 7.4 GHz using a calorimetric technique and showed two transitions, one at ∼8 K and another at ∼14 K; values of Rs were at least two orders of magnitude higher than similar high quality Nb3Sn films directly deposited substrates by JLAB and with another superconducting transition close to the superconducting transition temperature of niobium. Substantial improvements in the processing variables ranging from higher quality of the initial ingots with higher Sn content, to better electro-polishing and reaction heat treatment regimens will be necessary to realize improved RF performance metrics.

Influence of heat treatment regimens on the characteristics of poultry products using targeted fermentation application

The article reveals some aspects of the influence of the duration of heat treatment and different types of functional mixtures on the functional and technological characteristics of broiler meat products at low temperature processing under the condition of target fermentation. Broiler meat has several advantages for use as a raw material in the production of Sous-Vide products. These advantages include high moisture content, high organoleptic characteristics, and relatively low cost of this raw material. However, there are a few disadvantages that complicate the processing of broiler chicken meat by Sous Vide technology. These include the high amount of moisture released during production and the low moisture-binding capacity of some batches of raw materials (often associated with excessive moisture or disruption of autolytic processes in broiler chickens). To achieve the desired consistency and high organoleptic characteristics, enzyme preparations are widely used in the meat processing industry. To eliminate these shortcomings, it is proposed to use functional mixtures, which are introduced into the raw meat by injection, as well as the use of targeted fermentation. During the experiment, 2 formulations of broiler chicken meat products were developed, which in turn were treated in two heat treatment regimens and treated with the enzyme transglutaminase. In the first batch of samples, an injection of 15% solution of a functional mixture based on citrates was used, while in the second batch - a similar level of injection of a mixture based on phosphates. Heat treatment was performed after pre-application in bags and vacuum at 62 ℃ for 120 and 140 min for different groups of samples. In all samples, the yield of the finished product, the relative weight of the separated moisture (broth) in the package, the values of pH, water holding and moisture-retaining capacities, as well as the total moisture content in the finished product were determined. According to the obtained results, the optimal is samples with the use of phosphates, and 120 minutes the duration treatment is 120 minutes.

Strengthening mechanisms of creep-resistant 12%Cr–3%Co steel with low N and high B contents

The contributions from the martensitic laths, dislocations, secondary phase particles, and supersaturated solid solutions to the overall strength of the 12%Cr–3%Co–2.5%W creep-resistant steel with low N and high B contents were calculated after various heat treatments consisting of normalizing followed by medium-temperature tempering. An increase in the normalizing temperature from 1050 to 1150 °C led to an increase in the average size of the prior austenitic grains from 44 to 68 μm, but the δ-ferrite fraction did not significantly change. Medium-temperature tempering in the range of 750–800 °C ensured the formation of a tempered martensite lath structure with an average martensitic lath/subgrain size of 0.23–0.34 μm, along with a high dislocation density inside the laths/subgrains, fine secondary phase particles such as M23C6 carbides along the boundaries of the prior austenite grains, packets, blocks, and martensitic laths/subgrains, and (Ta,Nb)X carbonitrides uniformly distributed inside the matrix. After medium-temperature tempering in the range of 750–800 °C, the ferritic matrix was supersaturated with substitutional elements such as Cr, W, Mo, and Cu. An increase in the tempering temperature from 750 to 800 °C led to decreases in the yield strength and ultimate tensile strength by 16.2% and 10.5%, respectively, as well as an increase in the elongation of 43.8%. The main contributions to the overall strengthening of the steel investigated after the different heat treatment regimens produced solid solution strengthening and precipitation hardening, which were independent of the tempering temperature, as well as lath boundary and dislocation strengthening, which was strongly dependent on the tempering temperature. Different approaches for evaluating the strengthening mechanisms and their contributions to the yield strength were applied, and the results are discussed.

Improved Post-Weld Heat Treatment for Argon TIG Welded Joint of a New Al – Zn – Mg – Cu Alloy

An argon TIG welded joint of the Al – Zn –Mg – Cu alloy was studied. Based on the hardness and differential scanning calorimetry studies, a post-weld alloy heat treatment regimen has been proposed to ensure a welded joint strength of 622 MPa versus the strength of the base metal of 676 MPa. The post-weld heat treatment provides for a two-stage solid solution treatment (470°C, 90 min + 500°C, 20 min) and artificial aging at 120°C for 24 h.

Additive Manufacturing of 17-4 PH Stainless Steel: Post-processing Heat Treatment to Achieve Uniform Reproducible Microstructure

17-4 precipitation hardenable (PH) stainless steel is a useful material when a combination of high strength and good corrosion resistance up to about 315°C is required. In the wrought form, this steel has a fully martensitic structure that can be strengthened by precipitation of fine Cu-rich face-centered cubic phase upon aging. When fabricated via additive manufacturing (AM), specifically laser powder-bed fusion, 17-4 PH steel exhibits a dendritic structure containing a substantial fraction of nearly 50% of retained austenite along with body centered cubic/martensite and fine niobium carbides preferentially aligned along interdendritic boundaries. The effect of post-build thermal processing on the material microstructure is studied in comparison to that of conventionally produced wrought 17-4 PH with the intention of creating a more uniform, fully martensitic microstructure. The recommended stress relief heat treatment currently employed in industry for post-processing of AM 17-4 PH steel is found to have little effect on the as-built dendritic microstructure. It is found that, by implementing the recommended homogenization heat treatment regimen of Aerospace Materials Specification 5355 for CB7Cu-1, a casting alloy analog to 17-4 PH, the dendritic solidification structure is eliminated, resulting in a microstructure containing about 90% martensite with 10% retained austenite.

Defining immunological impact and therapeutic benefit of mild heating in a murine model of arthritis.

Traditional treatments, including a variety of thermal therapies have been known since ancient times to provide relief from rheumatoid arthritis (RA) symptoms. However, a general absence of information on how heating affects molecular or immunological targets relevant to RA has limited heat treatment (HT) to the category of treatments known as “alternative therapies”. In this study, we evaluated the effectiveness of mild HT in a collagen-induced arthritis (CIA) model which has been used in many previous studies to evaluate newer pharmacological approaches for the treatment of RA, and tested whether inflammatory immune activity was altered. We also compared the effect of HT to methotrexate, a well characterized pharmacological treatment for RA. CIA mice were treated with either a single HT for several hours or daily 30 minute HT. Disease progression and macrophage infiltration were evaluated. We found that both HT regimens significantly reduced arthritis disease severity and macrophage infiltration into inflamed joints. Surprisingly, HT was as efficient as methotrexate in controlling disease progression. At the molecular level, HT suppressed TNF-α while increasing production of IL-10. We also observed an induction of HSP70 and a reduction in both NF-κB and HIF-1α in inflamed tissues. Additionally, using activated macrophages in vitro, we found that HT reduced production of pro-inflammatory cytokines, an effect which is correlated to induction of HSF-1 and HSP70 and inhibition of NF-κB and STAT activation. Our findings demonstrate a significant therapeutic benefit of HT in controlling arthritis progression in a clinically relevant mouse model, with an efficacy similar to methotrexate. Mechanistically, HT targets highly relevant anti-inflammatory pathways which strongly support its increased study for use in clinical trials for RA.

Effects of preincubation heating of broiler hatching eggs during storage, flock age, and length of storage period on hatchability

The effects of heating of eggs during storage, broiler breeder age, and length of egg storage on hatchability of fertile eggs were examined in this study. Eggs were collected from Ross 344 male × Ross 308 broiler breeders on paper flats, held overnight (1 d) at 18°C and 75% RH, and then transferred to plastic trays. In experiment 1, eggs were obtained at 28, 38, and 53 wk of flock age. During a further 10 d of storage, eggs either remained in the storage room (control) or were subjected to a heat treatment regimen of 26°C for 2 h, 37.8°C for 3 h, and 26°C for 2 h in a setter at d 5 of storage. In experiment 2, eggs from a flock at 28 wk of age were heated for 1 d of a 6-d storage period. Eggs from a 29-wk-old flock were either heated at d 1 or 5 of an 11-d storage period in experiment 3. In experiment 4, 27-wk-old flock eggs were heated twice at d 1 and 5 of an 11-d storage period. Control eggs stored for 6 or 11 d were coincubated as appropriate in each experiment. Heating eggs at d 5 of an 11-d storage period increased hatchability in experiment 1. Although no benefit of heating 28-wk-old flock eggs during 6 d of storage in experiment 2 was observed, heating eggs from a 29-wk-old flock at d 1 or 5 of an 11-d storage period increased hatchability in experiment 3. Further, heating eggs from a 27-wk-old flock twice during 11 d of storage increased hatchability in experiment 4. These effects were probably due to the fact that eggs from younger flocks had been reported to have many embryos at a stage of development where the hypoblast had not yet fully developed (less than EG-K12 to EG-K13), such that heating during extended storage advanced these embryos to a more resistant stage.

Heat-treated microstructure and mechanical properties of laser solid forming Ti-6Al-4V alloy

The effects of heat treatment on the microstructure and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy were investigated. The influences of the temperature and time of solution treatment and aging treatment were analyzed. The results show that the microstructure of LSFed samples consists of Widmanstatten α laths and a little acicular in columnar prior β grains with an average grain width of 300 µm, which grow epitaxially from the substrate along the deposition direction (Z). Solution treatment had an important effect on the width, aspect ratio, and volume fraction of primary and secondary α laths, and aging treatment mainly affects the aspect ratio and volume fraction of primary α laths and the width and volume fraction of secondary α laths. Globular α phase was first observed in LSFed samples when the samples were heat treated with solution treatment (950°C, 8 h/air cooling (AC)) or with solution treatment (950°C, 1 h/AC) and aging treatment (550°C, above 8 h/AC), respectively. The coarsening and globularization mechanisms of α phase in LSFed Ti-6Al-4V alloy during heat treatment were presented. To obtain good integrated mechanical properties for LSFed Ti-6Al-4V alloys, an optimized heat treatment regimen was suggested.

Optimal Design of Alloy Steels Using Multiobjective Genetic Algorithms

ABSTRACT Determining the optimal heat treatment regimen and the required weight percentages for the chemical composites to obtain the desired mechanical properties of steel is a challenging problem for the steel industry. To tackle what is in essence an optimization problem, several neural network-based models, which were developed in the early stage of this research work, are used to predict the mechanical properties of steel such as the tensile strength (TS), the reduction of area (ROA), and the elongation. Because these predictive models are generally data driven, such predictions should be treated carefully. In this research work, evolutionary multiobjective (EMO) optimization algorithms are exploited not only to obtain the targeted mechanical properties but also to consider the reliability of the predictions. To facilitate the implementation of a broad range of single-objective and multi-objective algorithms, a versatile Windows 2000®-based application is developed. The obtained results from the single-objective and the multiobjective optimization algorithms are presented and compared, and it is shown that the EMO techniques can be effectively used to deal with such optimization problems.

Prediction of treatment temperatures in clinical hyperthermia of locally advanced breast carcinoma: The use of contrast enhanced computed tomography

Purpose : Nineteen patients with locally advanced breast carcinoma were subjected to computed tomography examinations prior to thermoradiotherapy. Pre- and postcontrast computed tomography images were obtained, and tumor contrast enhancement was studied in relation to tissue perfusion, PERF, and steady state temperature, T S , in an attempt to develop an assay for prediction of treatment temperatures in clinical hyperthermia of breast carcinoma. Methods and Materials : PERF and T S were calculated from temperature data achieved during the first fraction of the heat treatment regimen. The computed tomography images were subjected to image analysis, and two parameters representing tumor contrast enhancement were calculated from the computed tomography numbers; the absolute increase in mean attenuation, δN, and the fraction of the postcontrast attenuation values that was higher than the mean precontrast attenuation value, F + C . Results : δN and F + C were clearly correlated to each other. The two parameters differed considerably among the patients, showing that the accumulation of contrast medium was higher in some tumors than in others. Tumor contrast enhancement increased with increasing PERF, suggesting that the accumulation of contrast medium in the tumors was determined mainly by the effective tissue perfusion. There was also a clear correlation between tumor contrast enhancement and T S . The tumors showing a high accumulation of contrast medium were more difficult to heat than those showing a low accumulation. Conclusion : The results indicate that contrast enhanced computed tomography images may give information about the treatment temperatures that can be achieved in clinical hyperthermia of breast carcinoma. The computed tomography images may possibly be used to predict those tumors that can be heated to therapeutic temperatures.