Heat Treatment Conditions Research Articles

Direct artificial aging of the PBF-LB AlSi10Mg alloy designed to enhance the trade-off between strength and residual stress relief

The AlSi10Mg alloy is one of the most studied alloys processed by the Powder Bed Fusion-Laser Beam (PBF-LB). Many already published works focus on post-process heat treatments to reduce residual stress or improve mechanical strength. Instead, the present study aims to identify direct artificial aging (AA) heat treatment able to optimize both aspects, thus enhancing the trade-off between strengthening and residual stress relief for the PBF-LB AlSi10Mg alloy produced using a no-heated platform. Higher temperatures (190–240 °C) than those typically used in AA heat treatment were selected based on thermal analysis to benefit both residual stress relief and precipitation of reinforcing phases from the supersaturated solid solution of the metastable as-built alloy. The effects of AA heat treatment on mechanical properties (i.e. hardness) and residual stress were evaluated by plotting aging curves and by XRD and Raman analyses and demonstrated that different trade-offs between strengthening and stress relief can be achieved by tuning heat treatment parameters (temperature and time). In particular, the exposure at the lowest temperature (190 °C) induced a partial decrease in residual stress and a slight increase in hardness. By increasing heat treatment temperature and soaking time, the relief was more significant, whilst the decrease in hardness was rather limited. The results are supported by the microstructural changes observed on the samples due to the different heat treatment conditions applied and show the feasibility of designing an AA heat treatment for the PBF-LB AlSi10Mg alloy capable of satisfying the mechanical response required by the final application.

STUDY ON THE IMPACT OF POST WELD HEAT TREATMENT ON TIG AND A-TIG INCONEL 617 WELDMENTS

This study analyzes the effects of Post Weld Heat Treatment (PWHT) on the mechanical properties and microstructure of Inconel 617 weldments produced by the Activated Tungsten Inert Gas (A-TIG) welding and Tungsten Inert Gas (TIG) welding. The TIG weld joints considered for this study were in an as-welded condition and underwent two different conditions of heat treatment including 1050∘C for 3 and 5[Formula: see text]h, respectively. The A-TIG weld joints studied were the as-welded type and the weldment was heat-treated at 1050∘C for 3[Formula: see text]h. The microstructure and the characterization of mechanical properties were performed for all weldments and a comparative assessment was made. Tensile strength and the hardness of the heat-treated samples were considerably higher than that of the as-welded samples. Impact toughness was slightly reduced after PWHT. Improvement in tensile strength could be attributed to the precipitation of the carbides and segregation of Chromium (Cr) and molybdenum (Mo).

Directed Energy Deposition‐Arc Repair Al6.5Cu2Ni0.3Ti0.5Zr0.25V Alloy: Microstructure Evolution and Strengthening Mechanism

Casting Al6.5Cu2Ni0.3Ti0.5Zr0.25V alloy is applied to aircraft engine components, but the casting defects are difficult to avoid. In this research, the local defects of casting heat‐resistant Al6.5Cu2Ni0.3Ti0.5Zr0.25V alloy parts are repaired by the arc‐directed energy deposition method. To examine the mechanism of the microstructure in the repaired zone of the heat treatment condition on the high‐temperature characteristics, the microstructure evolution of the repaired zone before and after heat treatment is analyzed. The results indicate that stratification exists in the sedimentary layer, however, the overall grain distribution is relatively uniform. After heat treatment, the microstructure of the repaired zone is changed, Cu element distribution becomes uniform and dendrite segregation disappears; simultaneously, the grain in the repaired zone mainly exists as high angle grain boundaries, which improves the fracture resistance ability of the material. At 350 °C, the average tensile strength, yield strength and elongation are 120.0 MPa, 98.6 MPa and 12.9%, respectively, the tensile strength reaches 94.1% of the matrix. Dimples abound on the fracture's exterior, and the fracture form of the repaired zone is microporous aggregate fracture. δ‐Al3CuNi and γ‐Al7Cu4Ni enhance the grain boundary strength, and θ′‐Al2Cu diffuses from the α‐Al matrix during aging, which is the main reason for the excellent high‐temperature performance of the repaired zone.

Controlling phase transitions in MnNiGe using thermal quenching and hydrostatic pressure

Abstract The phase transitions in MnNiGe compounds were explored by manipulating the heat treatment conditions and through hydrostatic pressure application. As the quenching temperature increased, both the first-order martensitic structural transition temperatures and magnetic transition temperatures decreased relative to those in the slowly-cooled samples. When the samples were quenched from 1200 ℃, the first-order martensitic structural transition temperature lowered by more than 200 K. The structural transitions also shifted to lower temperature with the application of hydrostatic pressure during measurement. Temperature-dependent X-ray diffraction results reveal
that the changes of the cell parameters resulting from the structural transitions are nearly identical for all samples regardless of the extensive variation in their structural transition temperatures. In addition, neutron scattering measurements confirm the magnetic structure transition between simple and cycloidal spiral magnetic structures.

Effect of Build Geometry and Porosity in Additively Manufactured CuCrZr

Abstract The current work presents an understanding of microstructure and mechanical properties as a function of build geometry and build orientation in Cu-Cr-Zr via the laser powder bed fusion (LPBF) technique. Porosity, microstructure, and mechanical properties have been compared in as-printed (AP) and heat-treated (HT) LPBF Cu-Cr-Zr, between cylindrical and cube geometries, along the longitudinal (L) and transverse (T) build orientations. Varying porosity levels were observed that yielded parts with 96–97% relative density in the AP condition. The AP microstructure demonstrated a hierarchical microstructure, comprising grains (2.5–100 μm) with a cellular substructure (400–850 nm) and intracellular nanoscale (20–60 nm) precipitates. Unlike most materials in the AP condition, crystallographic texture was found to be absent; however, very distinct river-like patterns highlighted a novel feature of the LPBF Cu-Cr-Zr. Upon solutionizing and aging, Cr precipitates were seen heterogeneously nucleating along cell boundaries (0.5–1.3 μm), causing up to 45% enhancement in the strength and a 4–5% lower ductility. The yield strength along the transverse orientation was 10–16% higher than that of longitudinal orientation, in both the AP and HT conditions. Fracture surface of the tensile samples exhibited micro-voids, cleavage facets, and unmelted particles. Despite the porosity, overall mechanical properties matched well with those obtained in nearly dense (>99%) samples and the mechanical property debit was less than 10%.

Improvement of micro/nano-structure and corrosion resistance of TiCu alloy by addition of tin and their Sr-hydroxyapatite coating

This study explores the influence of tin (Sn) content on the properties of Ti7CuXSn (X = 2, 7, and 15 wt%) alloys, in both as-cast and heat-treated conditions. The investigation reveals that an elevated Sn content within the Ti7Cu alloy results in the formation of finer grain structures. Rapid quenching processes lead to the development of an ultrafine martensitic structure and the formation of (Ti,Sn)2Cu intermetallic compounds within the Ti7CuXSn alloys. Subsequent heat treatment processes induce the transformation of the ultrafine martensitic structure into a coarser one, accompanied by an increase in the volume fraction of (Ti,Sn)2Cu. X-ray diffraction (XRD) analysis validates the presence of α/α'-Ti(Sn,Cu) phases and (Ti,Sn)2Cu intermetallics across all alloy compositions. The Ti7Cu15Sn alloy demonstrates higher microhardness, primarily attributed to its smaller grain size, reduced lamellar spacing, and increased volume fraction of (Ti,Sn)2Cu. Furthermore, all specimens exhibit heightened microhardness following heat treatment due to the martensitic structure with heterogeneous and homogeneous nucleation of (Ti,Sn)2Cu intermediate growth. Electrochemical analysis reveals an enhanced corrosion resistance in the Ti7Cu15Sn alloy, attributed to its elevated Sn content. Nonetheless, the as-cast Ti7Cu15Sn alloy displays superior corrosion resistance, albeit with a marginal reduction in electrochemical performance following heat treatment. Surface characterization signifies the formation of a uniform oxide film, underscoring commendable corrosion resistance in both as-cast and heat-treated Ti7CuXSn alloys. Additionally, the study investigates the deposition of strontium (Sr)-doped ceramic coatings on as-cast Ti7Cu15Sn alloys. It is demonstrated that higher current density parameters yield denser and more crystalline Sr-HA coatings. Energy dispersive spectroscopy (EDS) mapping confirms the successful incorporation of Sr into the coating, showcasing its potential for applications in the field of biomedicine. Thus, this investigation highlights the significant impact of Sn content on microstructural refinement, enhancements in mechanical properties, and improved electrochemical performance within Ti7CuXSn alloys. These findings offer valuable insights for the design and optimization of alloy performance in diverse applications.

Development of a Mathematical Model of the Distribution of the Temperature Field in the Material of the Protective Coating of Pipe Metal Based on Low Molecular Weight Oligodiene During its Heat Treatment

Statement of the problem. The process of vulcanization of the material of the protective coating of pipe metal based on low molecular weight oligodiene is possible only when creating and maintaining the specified temperature conditions in terms of the volume of vulcanizate. To study the regularities of the distribution of temperature fields in the vulcanized coating and to ensure the necessary temperature conditions of heat treatment, taking into account the influence of external influences, it became necessary to develop a mathematical model of the distribution of the temperature field in the protective coating material during its heat treatment using induction heating. Results. A mathematical model of the distribution of the temperature field in the vulcanized coating of pipe metal based on low molecular weight oligodiene has been developed. Conclusions. The conducted computational experiment using a mathematical model of the distribution of the temperature field made it possible to determine compliance with the temperature regime of vulcanization of the protective coating material over the entire volume of vulcanizate under certain boundary conditions.

Effect of Aging Heat Treatment in an Al-4008 Produced by Liquid Metal Printing

In today's world, additive manufacturing (AM) is one of the most popular technologies and has the potential to revolutionize the manufacturing industry. As one of the most recent advances in this industry, liquid metal printing has a growing value in the engineering field. This study aims to evaluate the effect of two heat treatment conditions in an Al-4008 alloy produced by this technique in the microstructure and mechanical properties. It was concluded that the heat treatment (HT) enhances the Si particle coalescence and Fe-rich intermetallic compound precipitation, increasing the sample hardness significantly (50%). Density analysis showed a slight porosity decrease with HT. Tensile tests indicated heat-treated, same-directionally pulled samples exhibited brittleness compared to as-printed ones, while HT increased both yield strength (245 MPa) and ultimate tensile strength (294 MPa).

Wear and Corrosion Resistant Eutectic High-Entropy Alloy Al0.3CoCrFeNiMo0.75 Produced by Laser Metal Deposition and Spark-Plasma Sintering

Eutectic high-entropy alloys (EHEAs) with a fine-lamellar structure and homogenous property profile are of particular interest for wear and corrosion protection coatings. High cooling rates in the laser metal deposition (LMD) process can induce microstructure refinement and allow the formation of a supersaturated solid solution in EHEAs. A subsequent solution annealing can create the equilibrium state. In the present study, LMD coatings with an ultrafine-grained Widmanstätten structure were produced from the EHEA Al0.3CoCrFeNiMo0.75 gas atomized powder. High cooling rates during deposition led to a supersaturated solid solution with face-centered cubic (FCC) structure. The LMD coating exhibits the highest average hardness of 734 HV0.5, which drops to approx. 200 HV0.5 due to an increased microstructural domain size after heat treatment. Under oscillating wear, the formation of oxidized wear debris promotes material removal in the heat-treated condition. Corrosion tests reveal a deterioration of the passivation behavior. LMD processes exhibit great potential to create supersaturated solid solutions with refined structure in EHEAs to enhance the property profile.

Effect of heat treatment on microstructural characteristics and mechanical properties of hypereutectic B390 aluminium alloys modified by phosphorus and bismuth

This study investigated the effects of solution treatment and aging processes on microstructural characteristics and mechanical properties of hypereutectic B390 Al-Si Alloy modified by phosphorus (P) and bismuth (Bi). The morphology evolution of primary Si, eutectic Si, intermetallic compounds, and secondary dendrite arm spacing (SDAS) of both initial and modified alloys were investigated in as-cast and heat-treated conditions. It was found that the combination of 0.1 wt%P and 0.5 wt%Bi in B390 alloy resulted in a remarkable modification and refinement of primary Si, eutectic Si, and SDAS compared to initial specimens in the as-cast condition. After heat treating, the fine lamellar eutectic Si and intermetallic compounds underwent a higher degree of fragmentation and coarsening, appearing as small round particles, leading to a more pronounced formation of a supersaturated solid solution. Additionally, the peak aging time of the B390-P-Bi alloy was only 7 h, 2 h less than the initial specimen. After T6 treatment and addition of both 0.1 wt%P and 0.5 wt%Bi, the B390-P-Bi alloy exhibited a smaller rounded Mg3Bi2 phase at peak aging with a 62.07% size reduction compared to the B390-Bi alloy. The results show that adding P with Bi enhanced hardness, ultimate tensile strength (UTS) and elongation because of refinement of the SDAS, primary Si and eutectic Si. These refinements played a crucial role in increasing tensile strength by more effective strengthening through precipitation and grain size reduction. The B390-P-Bi alloy is a promising choice for applications requiring a balance between strength and ductility.

Energy absorption of AlSi10Mg origami cellular structures fabricated via laser powder bed fusion

We experimentally study the energy absorption of metallic origami cellular structures additively manufactured from an AlSi10Mg alloy. We fabricate AlSi10Mg origami using the laser powder bed fusion (L-PBF) process. Since the as-fabricated AlSi10Mg has limited elongation at break, we systematically examine the heat treatment conditions and achieve the large deformation (i.e., wide folding range) of AlSi10Mg origami without fracture of origami creases. In addition, we use a drop tower impact system to demonstrate the effectiveness of AlSi10Mg origami’s folding behavior for impact energy absorption. Based on our experimental results, AlSi10Mg origami cellular structures could be exploited to develop a highly efficient lightweight impact absorber.Graphical abstract

Surveying the Effects of Aging a High C-Containing Co-Based Superalloy From the As-Cast and Solution Heat-Treated Conditions

The microstructure of the high carbon-containing cobalt-based superalloy, Co-101, has been studied in the as-cast state and following a variety of heat treatments. In the as-cast state both M7C3 and Mo-rich M23C6 carbides were observed in the interdendritic regions. After thermal exposure at temperatures between 1000 °C and 1250 °C for 1, 10, and 100 hours, the M7C3 interdendritic carbide network was observed to transform into a Mo-lean M23C6 carbide. These changes were rationalized with thermodynamic calculations. The carbide transformation liberated carbide-forming elements that resulted in the precipitation of intragranular carbides in the dendritic regions at temperatures below 1150 °C. These carbides in the cast-aged material preferentially formed at the dendrite peripheries early during exposure, leading to wide particle size distributions. Peak hardness in the cast-aged material was attained within the first 10 hours of exposure and softening was observed thereafter. After solution heat treating at 1250 °C for 10 hours, the microstructure of Co-101 comprised an M23C6 interdendritic carbide network and solid solution dendrites supersaturated with carbide-forming elements. Subsequent aging of this microstructure for 100 hours at 900 °C led to a high number density and narrow particle size distribution of intragranular carbides. The characteristics of these carbides in the solution-aged material resulted in greater hardness, which was retained for longer durations of exposure, than the cast-aged specimens.

Prediction of Cross-Section-Dependent ADI Microstructures by Experimental Heat Treatment Simulation

Heavy section Austempered Ductile Iron (ADI) components may contain pearlitic or a mixed microstructure (mixture of pearlite and ausferrite) in their centres besides ausferrite. As a result, mechanical properties are not homogeneously distributed across the thicknesses of the components. The oversizing of the components therefore leads to unnecessary material expenses in foundries. In order to avoid the complex manufacturing process of heavy section ADI components and subsequent investigations, preliminary tests were performed with smaller test samples. Here, temperature-time curves were detected during heat treatment at different depths. Material samples of the customised composition were heat treated in a dilatometer under the same heat treatment conditions according to different sections of the cast component. A variation of the quenching rates was conducted to investigate the influence on the mixed microstructure formation and ratio of pearlitic and ausferritic microstructures. A comparison of the conventionally heat-treated and dilatometer produced microstructures proved the successful application for heavy section parts and enables microstructure predictions with small samples only. In this way, there is no requirement of expensive tests with high-mass components.

Evolution of the second phases in the weld seams of 2.25Cr-Mo-0.25 V steel in different heat treatment states

Abstract The evolution characteristics of the second phases in the weld seams of 2.25Cr-Mo-0.25 V steel in three states – welded, post-weld heat-treated and creep states – during manufacturing and service were evaluated by calculations and observations using optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction spectrometry. The results showed that the second phase was M 3C in the as-welded state. The types and quantities of the precipitated phases increased greatly after post-weld heat treatment (PWHT), and M 3C, M 2C, M 7C3, M 23C6 and MX were the main precipitated phases. During PWHT, the amount of M 7C3 decreased, the amounts of M 23C6 and MX increased, and the sizes of the second phases increased. The precipitates coarsened after long-term creep, and M 7C3, M 6C, M 23C6, M 2C, and MX were the main precipitate phases in this state. The size of the MX phase remained relatively stable during long-term creep, which contributed greatly to the creep resistance.

Effects of base plate temperature on microstructure evolution and high-temperature mechanical properties of IN718 processed by laser powder bed fusion using simulation and experiment

Base plate preheating is a relatively new strategy to influence the mechanical properties and microstructure of IN718. Base plate preheating was studied to reduce Niobium (Nb) segregation in the interdendritic region of IN718 superalloy and to improve mechanical properties through the laser powder bed fusion (L-PBF) process. Here, we compared experimental results for high-temperature (650℃) mechanical properties of specimens built with 200℃ (PH200) and 600℃ (PH600) preheated base plates. The as-built PH200 and PH600 specimens had relatively similar grain morphologies and orientations along the building direction. The PH200 specimen showed a cellular structure and higher Nb segregation at the interdendritic region, whereas the PH600 specimen had a dendritic structure and lower Nb segregation. The lower amount of Nb segregation in the PH600 specimen is mainly because of the cooling rate difference between specimens during the L-PBF process. The PH600 specimen exhibited slightly better tensile properties, longer creep life, and elongation than the PH200 specimen in both the as-built and heat-treated conditions. These differences mainly occurred due to differences in Laves and δ-phase fractions between the PH200 and PH600 specimens. The simulation result indicates that the temperature distribution in the block remains relatively uniform during the building process.

Localized Corrosion Resistance of Nickel Alloy 718 in Chloride-Containing Environments

Resistant to aggressive reducing environments and combining excellent mechanical properties, the age-hardenable Alloy 718 is the most broadly used nickel alloy in the oil and gas industry. Nevertheless, its localized corrosion resistance in oxidizing halide-containing environments has yet to be thoroughly investigated, with conflicting results discussed in the literature. In this regard, Alloy 718 has a relatively low pitting resistance equivalent, limiting in practice its use, where localized corrosion is expected, particularly in seawater applications. This work quantified the localized corrosion resistance of the alloy in chloride-containing environments. The potentiodynamic-galvanostatic-potentiodynamic (PD-GS-PD) technique was used to determine the crevice corrosion repassivation potential (ER,CREV) in deaerated natural seawater at different temperatures for two Alloy 718 grades (i.e., aerospace, as per ASTM B670, and oil and gas, as per API 6ACRA, grades). Additionally, PD polarization testing was conducted for the API 6ACRA grade in acidified solutions with varying chloride concentrations to simulate pit/crevice-like conditions. In the aerospace heat treatment condition, Alloy 718 suffered crevice corrosion at temperatures as low as 10°C, while the API 6ACRA grade remained unaffected at the same testing temperature. Stable crevice corrosion occurred at 20°C and 50°C for both grades.

A bifunctional cobalt catalyst for the synthesis of waxy diesel fuel by the Fischer–Tropsch method – from the development to implementation. Part 3. The experience of industrial implementation of the preparation technology

The work summarizes the results of testing the technology for preparing a bifunctional cobalt catalyst for the synthesis of hydrocarbons from CO and H2, obtained by extruding a mixture of Co-Al2O3 /SiO2 catalyst powders and HZSM-5 zeolite with a binder – boehmite in industrial conditions (2 batches of 50 kg each were prepared). The catalyst technology was implemented on the equipment of Ishimbay Specialized Chemical Catalyst Plant LLC. The obtained industrial samples of the catalyst were characterized by XRF, TPR H2, DTG, and tested in the synthesis of hydrocarbons from CO and H2 at a temperature of 250 °C, a pressure of 2.0 MPa, GHSV 1000 h–1. It has been shown that the implementation of the technology of a bifunctional cobalt catalyst for the production of low pour point diesel fuel in industrial conditions makes it possible to reproduce the characteristics of the catalyst obtained in laboratory conditions. The technology for producing the catalyst can be recommended for the production of industrial batches. It was determined that changes in the heat treatment conditions of the catalyst, as well as the presence/absence of a peptizer and pore former do not lead to a significant decrease in the productivity of C5+ hydrocarbons. The contentof the diesel fraction in C5+ products obtained from industrial samples of the catalyst remains at the level of the value obtained from the laboratory sample of the catalyst. At the same time, the low-temperature properties of diesel fuel obtained using all catalyst samples have similar values. Using an industrial sample synthesized without the use of a peptizing agent and a pore-forming component, the best lowtemperature properties of diesel fuel were achieved – the cloud point and fluid loss point were minus 16 and minus 24, respectively.

Integration of additive manufacturing and thermomechanical processing toward a hybrid production route for PH13-8Mo stainless steel

In the current study, PH13–8Mo is fabricated using laser-powder bed fusion and arc-directed energy deposition additive manufacturing (AM) processes. The microstructure and mechanical properties in the as-built and isothermally heat-treated conditions are studied. The isothermal heat treatment includes direct aging at 530 °C to form β-NiAl precipitates. The AM alloys (in the as-built condition) are then thermomechanically processed at the isothermal aging temperature to promote dynamic aging and dislocation multiplication. The resulting mechanical properties are found to be superior to the heat-treated conditions and correlated to the microstructure. This study paves the pathway toward developing a novel hybrid manufacturing route to fabricate alloys with exotic mechanical properties.

Processing, Microstructure, and Properties of Bimetallic Steel-Ni Alloy Powder HIP

This work explores technical feasibility in hot isostatic pressing (HIP) manufacturing of an integral bimetallic component using steel and Ni alloy powder for supercritical carbon dioxide (sCO2) turbomachinery. Lab-scale bimetallic HIP specimens using HAYNES® 282® and SS316L or SS415 powder are investigated in powder configuration, heat treatment, microstructure, and tensile properties up to 400 °C. Interdiffusion profiles at dissimilar alloy interfaces caused by HIP cycle is predicted by DICTRA simulations and validated by electron probe microanalysis (EPMA). The interdiffusion distance of most elements is around 100 μm, while C and N have a higher interdiffusion distance. Dense distribution of Ti-rich carbonitrides and alumina particles are found to decorate prior particle boundaries near joining interface on the 282 side, affecting tensile strength across interface as well as tensile failure location. A higher amount of excessive carbonitride formation near interface is observed in SS316L/282 than in SS415/282, which is consistent with the predicted greater degree of interdiffusion effect in SS316L/282. Typical HAYNES® 282® heat treatment condition is applicable to 282/SS316L and 282/SS415 combinations, resulting in a higher strength than cast CF8M and CA6NM. A pilot-scale bimetallic SS415/282 pipe is then demonstrated to show the promise of scaleup.

Effect of heat treatment on microstructure and properties of CrMnFeCoNiMo high entropy alloy coating

In this paper, CrMnFeCoNiMo high entropy alloy coating was prepared on 304 stainless steel by plasma cladding technology. The effects of different heat treatment processes on the microstructure, hardness, wear resistance and corrosion resistance of high entropy alloy coatings were studied. The XRD and SEM images of the coating show that the phase structure is mainly Ni–Cr–Co–Mo phase. The impurity phase-[CrFe] solid solution and Ni3Fe phase will be formed between 950 °C and 1050 °C. The homogenization effect of the coating composition is more excellent under the heat treatment conditions of 950 °C and more than 1 h holding time. The hardness of the coating is relatively high at 850 °C heat treatment temperature and holding for 1 h, which is 670 HV0.2. When the temperature rises to 950 °C and 1050 °C, the hardness of the coating decreases. The coating has relatively high wear resistance at 950 °C heat treatment temperature and holding for 1 h, and the friction coefficient is about 0.27. Moreover, under this heat treatment condition, the surface composition of the coating is uniform and the corrosion resistance is good. The self-corrosion current is 1.325 × 10−7 A and the self-corrosion potential is −0.202 V.