Post Heat Treatment Temperature Research Articles

Effects of annealing temperature on the formability, mechanical and interface properties of laminated metal composite STS304L/Al1050/STS430

Laminated metallic composites (LMCs) produced by cold roll bonding generate high plastic deformation. After the rolling process, it is essential to promote a post-heat treatment (PHT) to increase adhesion, minimize hardening, and enhance the formability of LMCs. In this research, the effects of PHT at low temperatures (250, 350, and 450°C) on LMCs (STS304/Al1050/STS430) obtained by cold rolling were investigated. The Forming Limit Curve (FLC) and mechanical properties such as ultimate tensile strength (σ_UT), yield strength (σ_Y), elongation (ε), and the anisotropy index (r-value) of the LMC were evaluated. Results indicate the best PHT temperature that combines formability, increased adhesion between layers, and better mechanical properties, such as elongation (ε), which increases from 37% to 55%. At this PHT temperature, the brittle intermetallic layer was not detected, and the FLC showed the best performance. Furthermore, in industrial applications, this PHT condition allows energy savings compared to PHT conditions of high process times (>12 h) and/or temperature (>500°C) reported by several works in the literature.

Study on low temperature and narrow heating bands of post weld heat treatment for girth welds stress reduction of long-distance pipelines

Residual stress affects the service safety of pipelines, but there are few efficient methods to reduce the residual stress, especially for long-distance pipelines with large diameters. In this paper, a Secondary Post Weld Heat Treatment (S-PWHT) stress reduction method with low temperature and two narrow heating bands is proposed, and this method fully considers the failure of the corrosion resistance layer caused by high temperature. The temperature distribution and stress distribution under different S-PWHT parameters are compared to obtain the optimal S-PWHT parameters using finite element numerical simulation. The thermocouples are conducted to verify the temperature, and the coercivity experiment is used to verify the stress distribution. Results show that two heating bands width of 80 mm and a peak temperature of 120 °C are the optimal S-PWHT parameters with the stress reduced by 61 %. Besides, the levels of stress reduction on the inner surface and the HAZ are higher than those on the outer surface and the base metal, respectively. The high-stress zone is transferred from the inner surface to the outer surface, and from the HAZ to the base metal. Furthermore, the stress reduction mechanism of S-PWHT has been revealed through constraint theory. Temperature change is the initial force, and the constraint is the driving force for stress reduction.

High efficiency Sb and Ag double doped Cu2ZnSn(S, Se)4 thin film solar cells realized by post-heat treatment process of heterojunction

Cu2ZnSn (S, Se)4 (CZTSSe) semiconductors have become a recent focus of research owing to their cost-effectiveness, environmental friendliness, and high efficiency. However, insufficient band alignment between the CZTSSe absorption layer and the CdS buffer layer significantly hampers the high conversion efficiency of CZTSSe devices. In this study, problems related to energy-band matching were solved by the post-heat treatment (PHT) of the absorber and buffer layers. Based on obtaining a high-quality absorption layer through double-doped (Cu, Ag)2Zn(Sn, Sb)(S, Se)4 (CAZTSSSe), the impact of the PHT process of CAZTSSSe/CdS on the device performance and heterojunction quality was investigated. The PHT process promoted the reciprocating motion of elements in the heterojunction region, directly inducing the movement of Cd towards the absorption layer and Cu towards the buffer layer. Furthermore, the PHT method enhances the recrystallization of CdS, resulting in the formation of a CdS layer with excellent crystalline quality. After PHT processing, a more favorable conduction band arrangement was obtained, which helps to reduce non-radiative recombination. Ultimately, when the PHT temperature reaches 200 °C, we get an optimal device with an efficiency of up to 9.44 %, as open circuit voltage (VOC) escalates to 431 mV, and lower fill factor (FF) attains 55.63 %. It is believed that this PHT process can be better applied in thin film cells to obtain high-efficiency solar cells.

Recovery of Ni-Co-Mn Oxides from End-of-Life Lithium-Ion Batteries for the Application of a Negative Temperature Coefficient Sensor

This study demonstrates the current advancements in battery management systems (BMSs), emphasizing the need for precise temperature monitoring within battery packs to enhance safety and performance through efficient thermal management. The increased demand for lithium-ion batteries (LIBs) has driven the development of temperature sensors with improved accuracy and stability. In particular, Ni-Co-Mn-based spinel oxides are commonly used due to their stable negative temperature coefficient (NTC) behavior. However, challenges arise in manufacturing due to the high cost and uncertain supply of critical cathode components (e.g., Co, Ni, and Mn) for LIBs. This research focuses on developing spinel-type (Ni0.6Co0.4Mn2)O4 using recycled Ni-Co-Mn oxides obtained from end-of-life (EOL) LIBs, demonstrating temperature resistance behavior suitable for temperature sensing. The oxides are prepared through hydrometallurgy, oxalate synthesis, and post-heat treatment. Successful integration into spinel-type NTC thermistors suggests broader applications in various industrial fields. A systematic investigation into the synthesis and characterization of recovered Ni-Co-Mn oxides from EOL LIB cathode materials (Li(Ni0.33Co0.33Mn0.33)O2) is presented for NTC thermistor application. Thermogravimetric analysis-derivative thermogravimetry (TGA-DTG) identifies the optimal post-heat treatment temperature. The X-ray diffraction (XRD) patterns confirm a cubic spinel structure of the Ni-Co-Mn oxides, supported by scanning electron microscope (SEM) images showing a uniform microstructure. Also, energy dispersive X-ray spectroscopy (EDS) mapping confirms homogeneous element distribution. Recovered oxide pellets from the sintering process exhibit a single spinel structure, with X-ray photoelectron spectroscopy (XPS) analysis revealing changes in the valence states for Ni and Mn. Resistivity measurements demonstrate semiconductive behavior, which shows a B value (3376.92 K) suitable for NTC thermistor applications. This study contributes valuable insights to black powder recycling from EOL LIBs and its potential in temperature-sensitive electronic devices.

Effect of Post-heat Treatment on Microstructure and Mechanical Properties of Laser Cladded High Co-Ni Secondary Hardening Steel Coating

The effect of post-heat treatment on the microstructure and microhardness of laser cladded high Co-Ni secondary hardening steel coating was investigated. The microstructures were analyzed using a SEM equipped with an EDS, and the microhardness was measured with a Vickers indenter. Decomposition of the retained austenite in the coating occurred during the post-heat treatment. As the temperature increased from 200 °C to 600 °C, the quantity of the retained austenite at the boundaries decreased significantly, while that of the needle-shaped M3C cementite and M2C carbides increased. The M2C carbides evidently coarsened when the temperature was higher than 500 °C. The microhardness of high Co-Ni steel coating increased as the temperature of post-heat treatment increased from 200 °C to 400 °C because the fine-scale M2C carbides were coherent with the matrix and increased distinctly in this temperature range. It decreased sharply when the temperature further increased from 500 °C to 600 °C due to both the incoherency of the coarsened M2C carbides and the recovery of dislocations in the carbon-supersaturated matrix.

Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat Treatment II: CaOx-ZrO2(1 − x) (x = 5–10 mol%)

The effects of CaO content and post-heat treatment were investigated on the phase stability and mechanical and thermal properties of Ca-PSZ. ZrO2 specimens with 5–10 mol% CaO were sintered, and post-heat treatment was performed at 1200 °C for 100 h. Subsequently, to test and analyze the crystal structure and the microstructure, the mechanical and thermal properties of the specimens were evaluated. All specimens were partially stabilized by 5–10 mol% CaO (5CSZ–10CSZ) in a mixed monoclinic and tetragonal phase; however, peaks of the secondary phase of CaZrO3 were observed in 10CSZ. The ratio of the monoclinic phase decreased from 62.50% (5CSZ) to 21.02% (10CSZ) as the CaO content increased. Additionally, the monoclinic phase ratio decreased from 59.38% (5CSZ) to 19.57% (9CSZ) after the post-heat treatment; an increase to 24.84% was observed for 10CSZ. An increase in Vickers hardness from 676.02 to 1256.25 HV and flexural strength from 437.7 to 842.7 MPa was observed with increasing CaO content. The post-heat treatment resulted in further increases in these values as the CaO content increased from 5CSZ to 9CSZ; however, the Vickers hardness and flexural strength of 10CSZ decreased by approximately 8% and 9%, respectively. The thermal expansion coefficient exhibited the same tendency as the mechanical properties. This coefficient increased from 8.229 × 10−6 to 9.448 × 10−6 K−1 with increasing CaO content and was enhanced after the post-heat treatment in 5CSZ to 9CSZ; however, the thermal expansion coefficient of 10CSZ decreased by approximately 4% after the post-heat treatment. The mechanically and thermally stable tetragonal phase increased, and the monoclinic phase decreased as the doped Ca replaced the Zr sites, as was confirmed by the X-ray diffraction (XRD) analysis. The post-heat treatment and the increased Ca addition further facilitated the replacement of Zr sites by Ca. However, at high Ca concentrations of 10CSZ, an equilibrium phase of CaZrO3 was formed as a secondary phase at the post-heat treatment temperature, resulting in low performance.

Estimation of surface roughness of direct metal laser sintered AlSi10Mg using artificial neural networks and response surface methodology

ABSTRACT Direct metal laser sintering (DMLS) is a metal-specific additive manufacturing (AM) technique that has grown in efficiency and precision due to compelling advancements in high-power lasers and fiber optics. This study examines the surface roughness of AlSi10Mg specimens manufactured additively using the DMLS technique. First, DMLS experiments were conducted with a range of control variables, including laser power, laser speed, orientation, and post-heat treatment temperatures. Later, surface roughness prediction models were developed using machine learning techniques and statistical methods such as artificial neural networks (ANN) and response surface methodology (RSM). The ANN model with an architecture of 4-9-9-1 is identified as the optimal network. The predictions of the ANN models were compared to those of the RSM models, and performance was quantified using the correlation coefficient (R-value) between predictions and the experimental data. The R-value of 0.96218 with experimental data and the least mean absolute percentage error (MAPE) of 0.9804% indicated that ANN predictions were more accurate than the RSM model estimates. Conclusive results prove that the developed ANN model accurately estimated the relationship between DMLS process parameters and surface roughness.

Effect of heat treatment temperature on the microstructure and microhardness of TiC/Ti6Al4V composite manufactured with laser metal deposition

This study presented the investigation of the influence of post heat treatment temperature on the microstructure and hardness of TiC/Ti6Al4V composite manufactured with laser metal deposition. Heat treatment was performed to improve the microstructural homogeneity. It was found that the addition of TiC into Ti6Al4V results in the formation of a Widmanstätten microstructure with different grain sizes on the matrix. Heat treatment of the TiC/Ti6Al4V promoted phase transformations from acicular in the as built to lamella (α + β) and equiaxial phases in the heat-treated samples. The 900°C heat treated sample showed a uniform distribution of α and β phases, and 1100°C showed an increase in β phases, which resulted in an equiaxial microstructure. Moreover, Heat treatment at 1100°C resulted in the highest microhardness of 665±13HV.

Effect of post-heat treatment on microstructure and mechanical properties of nickel-based superalloy fabricated by ultrasonic-assisted wire arc additive manufacturing

Ultrasound as a novel auxiliary means has been gradually used in additive manufacturing (AM) process. Ultrasonic cavitation and acoustic streaming can effectively control the columnar to equiaxed transition of grain structures, which can improve the anisotropy of mechanical properties. In addition, post-heat treatment (PHT) was considered to improve the microstructure uniformity and mechanical properties of alloys prepared by AM. In this study, we investigated the effect of PHT on the microstructure and mechanical properties of IN625 superalloy fabricated by ultrasonic-assisted wire arc additive manufacturing (UA-WAAM). The results showed that ultrasonic successfully inhibited the growth of columnar grains, and the microstructure was replaced by equiaxed grain structure. When the PHT temperature reached 1200 °C, the grain morphology changed, and a large number of annealing twins were generated in the alloy. Further, with the increase of PHT temperature, Laves phase disappeared and carbide particle size decreased. The results of mechanical properties showed that the microhardness and yield strength of the IN625 superalloy decreased with increasing PHT temperature, but the elongation and strain hardening ability increased significantly. The combination of UA and PHT provided an opportunity to achieve excellent strength-ductility balance in metals and alloys fabricated by AM.

Fabrication of bioresorbable hydroxyapatite bone grafts through the setting reaction of calcium phosphate cement.

We prepared hydroxyapatite (HAp) bone grafts by the setting reaction of calcium phosphate cement, and investigated the effects of the porosity and crystallinity on the osteoconductivity and bioresorbability. We examined the effect of the water-mixing ratio, pressure, and post-heat treatment temperature during preparation on the crystallite size and porosity of the HAp blocks. The quantity of protein adsorption increased with increasing porosity and specific surface area (SSA) of the HAp blocks, whereas the initial cell attachment was similar despite the different porosities and crystallinities. In in vitro dissolution tests with a pH 5.5 buffer, which mimics an osteoclast-created Howship's lacuna, both the porosity and SSA of the HAp blocks affected the solubility; most likely due to the increased contact area with the buffer. Thus, HAp blocks prepared by the setting reaction of calcium phosphate cement could be applicable for bioresorbable HAp bone grafts because of the high porosity and SSA.

Microstructure-gradient approach for effective determination of post-heat treatment temperature of an additive manufactured Ti-6Al-4V sample

In this paper, a Ti-6Al-4V wall was fabricated using wire and arc additive manufacturing to be as-deposited (AD) coupons for investigating the effect of post-heat treatments on microstructure and mechanical properties. A Gleeble thermal-mechanical simulator was used to create a microstructure gradient in the sample with different heat treatment temperatures to efficiently determine the optimal post-treatment temperature, which is followed by furnace heat treatments to find proper aging (Age) conditions. Solid solution at 830 ℃ for 2 h followed by water cooling + aging at 500 ℃ for 4 h followed by furnace cooling was considered to be the optimal post-heat treatment candidate because it gained a 12.85% improvement of yield strength (YS) and 3.33% improvement of the ultimate tensile strength (UTS), though tensile fracture elongation (EL) decreased 3.37% compared to the as-deposited samples. With this condition, microstructure evolution including β grains, α widmanstätten, grain boundary α (GB α), and α’ martensite was characterized at the same position of the sample experienced deposition (AD), solid-solution treatment (AD-ST), and aging (AD-ST-Age) respectively. The relationship between such step-by-step microstructure evolution with tensile strength as well as hardness change was analyzed and established. In the end, brittle fracture surfaces of AD, AD-ST, and AD-ST-Age samples were observed to find the factors that contribute to failure.

Effect of Post-Heat Treatment Temperature on Interfacial Mechanical Properties of Cold-Rolled Ti/Al Clad Material.

Titanium and titanium alloys possess low density, high specific strength, and excellent corrosion resistance, but are expensive and have low formability at room temperature. Therefore, to reduce cost and achieve excellent properties, titanium and titanium alloys are jointed with aluminum and its alloys, which are inexpensive and have low density and excellent room temperature formability. Cladding is a widely used solid-state bonding technique, and the post-heat treatment of titanium/aluminum clad materials is required to improve their interfacial properties, which is important to ensure the reliability of Ti/Al-clad materials. The interfacial properties of Ti/Al-clad materials are significantly affected by changes in the microstructure and mechanical properties after the post-heat treatment. Thus, in this study, the relationship between the microstructure and mechanical properties at the interface of Ti/Al-clad materials was analyzed after the post-heat treatment at several different temperatures. The thick diffusion and intermetallic compound layer was formed with post-heat treatment owing to the active diffusion of Al atoms. As a result, their uniaxial and nanomechanical properties were varied with the interfacial characteristics of the Ti/Al-clad material.

Effect of the HfO2/SiO2 pre-mixing ratio and heating temperature on the formation of HfSiO4 as a bond coat of environmental barrier coatings

As the operating temperature of advanced gas turbines typically exceeds 1400 °C, it has been required to replace conventional Si bond coat in environmental barrier coatings (EBCs) with materials possessing higher thermal stability. Since HfSiO4 has excellent thermal properties such as a high melting point, phase stability over 1400 °C, and CTE matches with that of the SiC-based ceramic matrix composites, it has attracted much attention as a next-generation bond coat material. In this study, HfSiO4 bond coat was successfully formed by atmospheric plasma spray with pre-mixed HfO2-SiO2 powders (molar ratios: 7:3 and 5:5) followed by heat treatment. Effect of molar ratios of the HfO2-SiO2 and post-heat treatment temperature (1375 and 1475 °C) on the formation of HfSiO4 were studied. An oxidation test of the HfSiO4 coating was carried out at 1475 °C with the conventional Si bond coat to verify whether the new bond coat was suitable for use in a thermal environment of 1400 °C or higher. From the results, the HfO2/SiO2 ratio of 5:5 was suitable for the formation of HfSiO4 than that of 7:3. After heat treatment at 1475 °C, the ratio of HfSiO4 phase was 84.35%. The higher content of HfSiO4 formed under 1475 °C, meaning the higher heat treatment temperature accelerated the HfSiO4 formation. In the oxidation test at 1475 °C, the new HfSiO4 bond coat showed no cracks and maintained its integrity, but the Si bond coat was oxidized and cracked severely. Therefore, it can be concluded that the new HfSiO4 bond coat formed from 5HfO2–5SiO2 coating is a potential candidate as a next-generation bond coat material in EBCs.

Microstructure control by heat treatment for better ductility and toughness of Ti-6Al-4V produced by laser powder bed fusion

ABSTRACT In this work, the effects of post-LPBF (laser powder bed fusion) heat treatments on microstructure evolution, tensile and Charpy properties of Ti-6Al-4V have been investigated. The results show that the original martensitic microstructure in the LPBF sample has converted to a lamellae mixture of α and β phases when post heat-treatment temperatures are below the β-transus (800°C, 850°C and 900°C) with air cooling. On this basis, a good balance of tensile strength and ductility was obtained from sample post heated at 800°C for 6 h followed by air-cooling, with an increase of ~42% in ductility and a significant toughness enhancement (almost 100% increase) compared to the as-built sample. The relationship betweenα lamellaethickness, β volume fraction and post-LPBF heat treatment has been established. Both α lamellae thickness and β volume fraction increase with the heat-treatment temperature.

Heterojunction post-heat treatment process driving high efficiency for Cu2ZnSnS4 solar cell

The quality of Cu2ZnSnS4 (CZTS) absorber layer, Mo/CZTS interface and heterojunction CZTS/CdS are the most important factors directly affecting the performance of CZTS solar cells. On the base of high quality absorber layer and back contact interface, the effects of post-heat treatment (PHT) process of CZTS/CdS on the quality of heterojunction and device performance have been comprehensively investigated. The PHT process can promote the elements in the heterojunction region interdiffuse between absorber and buffer layer, i.e., more Cd elements diffuse to CZTS, and Zn, Cu elements diffuse to CdS. Consequently, the elements interdiffusion affects the chemical composition of the absorber layer surface and the band alignment of the heterojunction. After applying the PHT process, the surface of CZTS becomes Cu-poorer in comparison to the CZTS bulk. Due to the diffusion of Cd2+into the CZTS layer, the free carrier density is increased. In addition, PHT process can also promote the recrystallization of CdS and thus greatly improve the crystallization quality of CdS. Owing to the more favorable band alignment at the CZTS/CdS interface as well as better crystallinity of CdS, higher quality heterojunction was obtained. Finally, at the optimized PHT temperature of 275 °C, a pure CZTS solar cell with active area efficiency of 9.75% (total area efficiency: 8.90%) has been fabricated. Based on the application of PHT process, reducing the deep level defects in CZTS bulk is expected to further improve the device performance.

Effect of post-heat treatment on residual stress and tensile strength of hybrid additive and subtractive manufacturing

This paper presents a comprehensive study of the tensile performance, heat treatment, fracture, decrease of residual stress, second-phase particle and microstructures of a 316L stainless steel fabricated by directed laser deposition (DLD) and thermal milling (starting milling temperature at 250 ± 50 °C), a typical hybrid additive and subtractive manufacturing process. Experiments of different post-heat treatment temperatures and tensile tests at room temperature were performed. The residual stress was eliminated with heat treatment at 400 °C for 2 h, and the average residual stress decreased 53.7% while the yield strength and ultimate strength decreased slightly. The fracture surfaces of different heat treatment temperatures were observed. The typical ductile fracture microstructures of dimples were seen in almost all specimens whenever the heat treatment temperature was low or high. The evolution of dimples from formation to destruction by heat treatment was analyzed. The different morphology and composition of the second-phase particles of different heat treatment temperatures were compared. The yield strength of 427.5 MPa, the ultimate strength of 599.27 MPa, and the elongation of 36.48% showed the new hybrid manufacturing technology could be used for further fabrication of components.

Synergetic effect of carbon and AlF3 coatings on the lithium titanium oxide anode material for high power lithium-ion batteries

A carbon coated commercial lithium titanium oxide (Li4Ti5O12; LTO) was acoustically mixed with nano-sized AlF3 and heat treated to form a simultaneous coating layer of carbon and AlF3 on LTO particles. The surface modified LTO samples were characterized by a variety of means such as X-ray diffraction, Fourier transform infrared spectrometer, high-resolution transmission electron microscope, and inductively coupled plasma mass spectrometry. The results indicate that both carbon and AlF3 layers exist on the surface of LTO particles and that the distribution of the carbon and AlF3 differs depending on post heat treatment temperature. The carbon and AlF3 coating layers formed by optimal post heat treatment at 350°C significantly improves electrochemical performance, which increases charge capacity by 30% over the pristine LTO after 50cycles at a high current density of 5C. Thus, LTO with a simultaneous coating layer of carbon and AlF3 formed by acoustic mixing and post heat treatment shows a potential to further improve commercially-optimized carbon-coated LTO by alleviating its inherently low conductivity. This is an effective way to stabilize the interface between LTO particles and electrolyte, and is a practical approach to promote the wide usage of LTO, one of the most potent anode materials.

CORROSION RESISTANCE OF UNS S31803 STAINLESS STEEL WELDED JOINTS

The corrosion resistance of duplex stainless steel welded joints is affected by different parameters such as filler metal chemical composition, heat input, shielding gas composition and post welding heat treatment temperature. In most cases such parameters interact with each other so that it is very difficult to foresee their effect on corrosion resistance of welded joints without specific experimental tests. In this work the best combination of shielding gas composition and post welding heat treatment temperature that guarantees the corrosion resistance of the joint according to ASTM A932, method C, was found. Two shielding gases were tested during welding, Ar (100%) and a mixture of Ar (87%), He (10%) and N (3%), while the solution temperatures were 1050 °C and 1070 °C. It was found that only the samples welded with the mixture of Ar (87%), He (10%), N (3%) as shielding gas and solution heat treated at 1070 °C passed the corrosion test completely.

Microstructure evolution induced by inoculants during the selective laser melting of IN718

This study focuses on the microstructure evolution induced by eutectic WC-W2C inoculants during the selective laser melting (SLM) of IN718. The as-built microstructure observed using an electron microscope indicates that grain nucleation occurred on the surface of inoculants and that the diffusion layer between inoculants and IN718 composed of a mixture of IN718 and inoculants. After the post heat treatment of the as-built SLM specimens, more grains nucleated around the inoculants, and Nb-rich precipitates were formed along the grain boundaries. With an increase in the post heat-treatment temperature, the microstructure evolution became more pronounced. To elucidate the underlying mechanism, both theoretical and experimental analyses were performed. In summary, eutectic WC-W2C inoculants could provide heterogeneous nucleation sites for grain formation owing to the low wetting angle and the semi-coherent interface with the matrix. Theoretical analysis suggests that the difference in the thermal expansion coefficient between inoculants and IN718 did not provide a significant amount of residual stress. Thus, it can be concluded that heterogeneous nucleation is the primary mechanism by which inoculants can influence the microstructure in the present study.

Effect of post-heat treatment on the mechanical properties of surface-tolerant epoxy coated on API 5L X65 carbon steel pipe: pipeline industry application

In the present work, a post-heat treatment was used to improve the mechanical properties of surface-tolerant epoxy coated API 5L grade X65 carbon steel pipe. For each carbon steel pipe coated with surface-tolerant epoxy, the mechanical properties including hardness and adhesive strength are measured by Shore D Durometer testing (impact resistance) and Hydraulic Adhesion tester (pull-off resistance). The mixing times, also known as the pot life timing, of the epoxy used in this experiment were 5, 15 and 30 minutes, and after mixing, the surface-tolerant epoxy’s viscosity was measured by Viscometer. The post-heat treatment temperatures of the fully cured surface-tolerant epoxy coated on the carbon steel pipe used in this study were room temperature, 50°C, 100°C, and 150°C over 24 hours. It was found that post-heat treatment results in the improvement of adhesive strength more than hardness. The maximum percentage of hardness and adhesive strength improvement after post-heat treatment was 6.47% and 37.04%, respectively.