Solution Heat Treatment Process Research Articles

Phase-field approach assisted solution heat treatment efficient design for novel multicomponent Co-based superalloys

Fast homogenization without incipient melting is the key to designing solution heat treatment (SHT) process for single crystal superalloys. In this paper, a multicomponent phase-field model coupled with solidus temperature is developed for dynamically tracking incipient melting temperature, TIM, of alloy during SHT. The simulation process runs completely automatically only by inputting the composition information of as-cast specimen. Based on the obtained TIM-time profile, the holding temperature and the time of SHT are determined. Applying this approach to Co–30Ni–11Al–4W–1Ta–4Ti–5Cr single crystal specimen, a gradual increased TIM from 1247 °C to 1293 °C within 72,000 s is obtained, and thus a stepwise SHT process with a short time of less than 20 h is designed. The experimental verification shows that after SHT, the segregation coefficient of the slowest diffusing element W decreased from more than 2 to 1.065, the content of harmful secondary phase has decreased to below 0.1%, and no incipient melting occurs.

New insights into the optimisation of the solution heat treatment process and properties of CMSX-4 superalloys

For nickel-based single-crystal superalloys, simultaneously reducing the segregation and optimising the microstructure is a primary challenge in the field of heat treatment. To further improve rupture life, the element partition, microstructure evolution, and creep behaviour of the second-generation nickel-based single-crystal superalloy CMSX-4 under five different solution processes were studied using electron microprobe, scanning electron microscopy, and transmission electron microscopy. Under the same conditions, both continuous heating and remelting heat treatment exhibited higher elements homogenisation efficiency. Moreover, it was found that the improvement of element segregation can make γ′ phase smaller and more uniform. These heat treatments reduced the incipient melting tendency or eliminated the incipient melting eutectic, thereby increasing the peak heat treatment temperature of the CMSX-4 alloy. However, remelting heat treatment results in a significant increase in the porosity of the alloy, leading to a deterioration in performance. Finally, based on the above study, a novel process combining stepwise heating and continuous heating was proposed, which not only increased the peak solid-solution temperature but also prevented the incipient melting and optimized the microstructure. After using the novel process, the durability of the alloy increased by 48 % from 240 to 356 h under the test conditions of 980 °C/250 MPa. The higher proportion of the γ′ phase, narrower matrix channel, and denser dislocation network were the main reasons for the improvement in the rupture life.

Effect of Heat Treatment and Anodizing of Aluminum 2024 on Hardness Test and Impact Test

Aluminum alloy 2024 is an alloy that is widely used in the aircraft industry, especially in the structure. This research was carried out with the Vikers hardness test method and the Charpy Impact test to determine the mechanical properties of the 2024 Aluminum alloy after going through the Solution heat treatment process with a temperature of 505oC with variations in natural aging time for 5, 7, 9, 11 days and through the Anodizing process with a time of 30 minutes and carried out Vikers hardness testing and Charpy Impact testing. The final results obtained in the Vickers hardness test obtained the highest average value in specimens that went through solution heat treatment with variations in natural aging time for 11 days and through the anodizing process of 80.2 HVN. Heat treatment and anodizing can improve mechanical properties in terms of toughness and hardness of the material, namely by using a stable temperature during heat treatment. In the Impact test, the highest average toughness value is obtained in specimens that go through solution heat treatment with a variation of natural aging time for 11 days and through the anodizing process of 0.76 J/mm². This shows that the Heat Treatment and Anodizing process affects the hardness and impact value of 2024 aluminum.

Effect of Solution Heat Treatment on the Microstructure and Microhardness of 7050 Aluminum Alloy

Today, 7xxx aluminum alloys are widely used in aerospace and other fields due to their excellent properties such as low density, high specific strength, and good processing performance. The heat treatment process of 7xxx aluminum alloy is crucial in controlling the strengthening phases and grain size, which is a significant way to enhance the alloy’s performance. In this study, solution heat treatment tests of 7050 aluminum alloys were carried out at different temperatures, ranging from 440 °C to 470 °C, with a holding time ranging from 0.5 h to 8 h, using a DIL 805A thermomechanical test machine. The microstructural evolution during the solution heat treatment was characterized using an optical microscope (OM), a scanning electron microscope (SEM), and a transmission electron microscope (TEM). The effects of the solution parameters on the alloy’s microhardness were analyzed using a digital Vickers microhardness tester. According to the ASTM E112-13 standard, The Anelli grain growth models were established to illustrate the grain size evolution during solution heat treatment, and a modified Anelli grain growth model was established. The results indicated that the grain size significantly increases with the increase in the solution heat treatment time and temperature. The Anelli grain growth model can illustrate the phenomenon of grain growth more accurately in the solution heat treatment process of 7050 aluminum alloy. It was found that prolonging the time and elevating the temperature of the solution heat treatment reduced the microhardness of the aluminum alloy because of the dissolution of the precipitates.

The Role of Boron Addition on Solidification Behavior and Microstructural Evolution of a High Niobium-Containing TiAl Alloy

This work investigates the role of boron addition in the solidification behavior and microstructural evolution during the heat treatment process of Ti-46Al-8Nb-xB (x = 0.1, 0.7, 1.4, 2.5 at.%). The results show that the solid solution boron element prefers to occupy the interstitial vacancies of the α2 phase in the alloy. However, the solid solubility of the boron element in high Nb-containing TiAl alloys is extremely low. Therefore, it does not have a significant effect on the lattice distortion of α2 and γ phases in the alloy. When the boron content is added up to 0.1%, a B27-type TiB precipitated phase is produced in the alloy. The morphology of borides mostly shows short rod-like structures, and a few show long curved shapes. And the addition of boron refines both the alloy colony size and the lamellar structure. Furthermore, it is also found that boron addition weakens the casting texture of the alloy. After a solid solution and different time aging heat treatment process, the microstructure of different boron content alloys have experienced obvious coarsening phenomenon. However, the morphology of the boride is closely related to boron content and heat treatment.

Evolution of Microstructure and Mechanical Properties of the Rheo-Diecast Mg-12Gd-3Y-1Zn-0.4Zr Alloy during Heat Treatment

The SEED (Swirled Enthalpy Equilibrium Device) process is the typical high solid fraction (with about 40-60% of solid) rheo-diecast process. The high strength Mg-12Gd-3Y-1Zn-0.4Zr magnesium alloy was successfully produced using SEED process. The microstructure and mechanical properties of rheo-diecast Mg-12Gd-3Y-1Zn-0.4Zr alloy during solution and ageing heat treatment process were studied in this paper. Optical microscopy (OM) and transmission electron microscopy (TEM) were employed to study the evolution of microstructure and mechanical properties. The cast alloy exhibited a microstructure consisting of equiaxed primary solidified grains and together with eutectics. The eutectics were partially dissolved into a-Mg matrix after solution heat treatment. The tensile properties of rheo-diecast Mg-12Gd-3Y-1Zn-0.4Zr alloy were substantially enhanced after T6 heat treatment.

Effects of heat treatments on the microstructure and tensile properties of IN738 superalloy with high carbon content fabricated via laser powder bed fusion

Heat treatment is a key process governing the final microstructure and mechanical properties of precipitation-hardened superalloys. However, traditional heat treatments are typically designed for cast or wrought superalloys. Therefore, this study investigates the effects of hot isostatic pressing (HIP) and a two-step heat treatment (THT) process that combines HIP with solution heat treatment (SHT) process. Heat treatments were conducted on a crack-free high carbon content IN738 alloy (IN738–0.3 C) fabricated via laser powder bed fusion (LPBF). HIP significantly reduced the porosity and residual stress of the LPBF IN738–0.3C samples. The HIP samples exhibited a large number of well-developed cuboidal γ′ precipitates (∼800 nm) and a few fine near-spherical γ′ precipitates (∼40 nm), whereas the THT samples had uniformly distributed γ′ precipitates with an average size of ∼80 nm. Therefore, the HIP and THT methods have potential to improve the properties of additive manufactured (AM) IN738 alloy. A superior combination of yield strength (1050 MPa), ultimate tensile strength (1295 MPa), and elongation (16.5 %) was achieved through THT. Additionally, the study revealed the detailed relationship between the microstructure and the mechanical properties. These results can serve as a reference for exploring suitable heat treatments for other AM precipitation-hardened Ni-based superalloys.

Precipitates evolution of the AA7075-H18 alloy sheet during the application of the solution heat treatment process

The hot stamping technology of the high-strength aluminum alloy sheet has attracted increased attention from both the scientific community and industry due to the rapidly growing demand for lightweight automobiles. However, the development of a proper solution process suitable for the hot stamping technique remains a great challenge. Along these lines, in this work, the precipitates evolution of the AA7075-H18 alloy sheet with a thickness of 2 mm during the implementation of the solution process was systematically studied. The insoluble particles (i.e., Al23CuFe4 and Mg2Si) and the soluble particles (η-MgZn2) were clearly identified from the aluminum matrix. Moreover, the transformation sequence during the solution heat treatment was determined, and a reasonable solution temperature window was also established.

The Effect of Solution Time on the Microstructure of A356.2 Aluminum Alloy Provided by Rheocasting and Squeeze Casting

The evolution of the microstructure of A356.2 alloys prepared by the rheocasting and squeeze casting during solution heat treatment was investigated. In contrast with the conventional solution heat treatment process (3 hours at 540oC), a short time solution treatment process (less than 1 hour at 540oC) is applied in this paper. The results show that the rheocastings require a shorter solution time than the squeeze-castings to obtain spheroidized Si particles. After solution for 10 min, the X-ray diffraction inspection results show that the Mg2Si phase completely is dissolved in both rheocastings and squeeze-castings. However, a small amount of Mg2Si is found at the edge of the Si particle by scanning electron microscope observation. After solution for more than 20 min, the Mg2Si phase is completely dissolved. Fe-rich phases, including AlSiFeMg and AlFeSi, exist throughout the solution process. The developed T6 heat treatment with a short solution time can effectively improve production efficiency and decrease process cost for the rheocasting process. Key words: A356.2 alloy, microstructure, short solution time, rheocasting, squeeze casting

Pengaruh Media Pendingin pada Perlakuan Panas T6 terhadap Kekuatan Tarik dan Struktur Mikro Komposit Al6061-Pasir pantai

Al6061-sea sand composite was manufactured using the stir casting method and its mechanical properties were improved by heat treatment. The T6 heat treatment used to improve the mechanical properties of the composite consists of the following processes: solution heat treatment, quenching, and artificial aging. The solution heat treatment process was carried out at a temperature of 540 o C for 6 hours. The quenching process was carried out with different quenching agents (water, oil, and 10% brine). The difference in quenching agents resulted in different cooling rates. After quenching, an artificial aging process was carried out at a temperature of 200 o C for 4 hours. The difference in cooling rate affects the hardness and tensile strength of the specimen. The high cooling rate results in an increase in the tensile strength of the specimen. This is due to the increase in cooling speed, the Mg 2 Si precipitates formed are smaller in size and located in the grains. The highest tensile strength of specimen (206.67 MPa) is obtained by using brine quenching agent.

Modeling of Isothermal Dissolution of Precipitates in a 6061 Aluminum Alloy Sheet during Solution Heat Treatment

During the solution heat treatment (SHT) process of aluminum alloys, precipitates dissolve into the matrix. To predict the dissolution time, modeling of isothermal dissolution of precipitates in 6061 aluminum alloy during SHT was conducted. A precipitate dissolution model was established, and the flowchart of the modeling was designed as well. Then the explicit finite-difference method was employed to solve the dissolution model, and the mobile nodes method was used to deal with the moving interface. The simulation was based on real precipitates in 6061, and SHT experiments were conducted to validate the numerical model. The simulation results showed that the isothermal dissolution time of precipitates in 6061-T6 aluminum alloy at 560 °C is 11.6856 s. The dissolution time in the simulation was close to the experimental results, with an error of 16.7%, indicating that the modeling in this study was fairly reasonable and accurate. The error was caused by many factors, and the model should be improved.

THE EFFECT OF SOLUTION HEAT TREATMENT HOLDING TIME VARIATIONS ON THE MECHANICAL PROPERTIES OF ALUMINUM A-6061 BY THE TIG WELDING PROCESS

Aluminum and its alloys are metals that are widely used in the engineering field because its have advantages including good formability, relatively high tensile strength, corrosion resistance and a welding process for the joints. General structure, structures that have poor mechanical properties. To overcome this problem, the material that has been welded is heat treated or heat treated according to temperature and time management) which is suitable in addition to good mechanical properties as well as to reduce residual stresses. The purpose of this research is to determine the tensile strength and hardness value of welding joints of Aluminum 6061 with a variation of Holding Time 1, 2, 3 hours in the Solution Heat Treatment process with a temperature of 5000C. The results showed that based on the results of the tensile test, it showed that the holding time affected the value of the tensile strength and strain of the welding joint where the highest tensile test value was at a holding time of 1 hour, while the highest strain value was at a holding time of 2 hours. Then from the hardness test data, it shows that the heating duration or holding time affects the hardness value of the material both in the weld metal, HAZ, and base metal areas. In the weld metal area, the highest hardness value is at a holding time of 3 hours. The HAZ area has the highest hardness value at a holding time of 2 hours, while the base metal region has the highest hardness value at a holding time of 1 hour.

Experimental investigation into microstructure, mechanical properties, and cracking mechanism of IN713LC processed by laser powder bed fusion

IN713LC is a Ni-based superalloy with extensive uses in the aerospace industry. However, fabricating IN713LC components using additive manufacturing technologies such as laser powder bed fusion (LPBF) is extremely challenging due to its high composition of alloying elements (e.g., Al and Ti), which increase its susceptibility to cracking. Accordingly, the present study conducts an experimental investigation into the LPBF processing parameters (i.e., laser power and scanning speed) which enable the fabrication of LPBF IN713LC parts with a high relative density and minimal cracking. The effects of heat treatment on the microstructure and mechanical properties of the as-built parts are then examined. The results show that IN713LC is prone to the two micro-cracking mechanisms, namely solidification cracking due to the formation of low-melting-point elements at the grain boundaries and ductility dip cracking (DDC) as a result of grain boundary sliding. However, given an appropriate selection of the LPBF processing conditions, as-built IN713LC components with an average yield strength of 800 MPa, an ultimate tensile strength of 998 MPa, and ultimate elongation of 12.5% at room temperature are better than those of as-cast IN713LC specimens. Notably, the solid solution heat treatment process yields a significant improvement in the yield strength compared to that of the as-built sample. Moreover, all the mechanical properties of the sample processed by solid solution heat treatment are comparable to those of the as-cast IN713LC sample.

Multiphase-field simulation of the solution heat treatment process in a Ni-based superalloy

New generation of nickel based single crystal superalloy requires complex solution heat treatment (SHT) procedures to improve its high temperature performance. However, the designation of SHT is difficult due to severe segregation, significant fraction of eutectic, and undesired incipient melting. The multiphase-field simulation coupled with thermodynamic calculation was used to investigate microstructure evolution and element distribution from solidification to SHT process in a superalloy. The simulated solidified microstructure was used as input for subsequent SHT simulation. And the simulation results were verified by experimental measurements in terms of the γ/γ' eutectic fraction and microsegregation pattern in the as-cast state and during each step of SHT. Based on the simulated microstructure and concentration, the incipient melting temperature was obtained by thermodynamic calculation. The results show that the region with lowest melting temperature is located at the boundary between γ dendrite and interdendritic bulk γ' phase, which is last solidification region. And incipient melting temperature gradually increases during SHT. Besides, the variation of γ' phase fraction under different holding temperatures was simulated, and calculated γ' reduction rate increases significantly with the temperature. The current work has demonstrated the ability of multiphase-field simulation and thermodynamic calculation in designing SHT procedures for complex superalloys.

Evaluation of AA6061-T6 behavior subjected to Cyclic Solution Treatment

The effects of the repeated solution heat treatment on hardness, tensile strength and microstructure of aluminum were studied. For this purpose, an alloy of AA6061-T6 was undergo to cyclic solution heat treatment process which is composed of repeated period (10 min) held at 520 °C for 1, 4, 8 and 12 cycles. The hardness was tested for five aging times (as quenching, one week, three weeks, one month and five months) to all cycles (1, 4, 8 and 12) firstly and it is found that the hardness of five months as aging time for all cycles has the best results (90Hv) as compared with others (as quenching, one week, three weeks, and one month), so it was adopted for all cycles to implement the tensile test and the microstructure. Hardness results were improved to Vickers hardness of (90Hv) with increasing of cycles up to 8 cycles then decreasing after that to (45Hv). Tensile results were showed an increment (34%) also for the same group of 8 cycles compared with (17%) and (9%) for 4 and 12 cycles, respectively. Microstructure is revealed that whenever cycles are increased, the precipitate phase in alloy is increased also, thus, it is improved the hardness and tensile strength.

Optimizing Heat Treatment Parameters for the W-Temper Forming of 7xxx Series Aluminum Alloys

A major challenge in processing 7xxx series aluminum alloys is their limited formability at room temperature. In this paper, for the alloys EN AW-7020 and EN AW-7075, various variants of the W-temper forming process are investigated. For both alloys, a good cold formability and a high strength after aging can be achieved. The effects of solution heat treatment or retrogression temperature and holding time, as well as the influence of plastic deformation after quenching, were studied. For various combinations of process parameters, the formability of the as-quenched materials and the hardening performance during artificial aging were examined. For this, hardness measurements and differential scanning calorimetry (DSC) experiments were performed along the entire process chain, to reveal the development of the hardening precipitates. After solution heat treatment and quenching, the yield stress and hardness of both investigated alloys were drastically reduced in comparison to their initial T6 states, while the ductility was significantly increased. By a subsequent simple artificial aging treatment, the same hardness as in the T6 state could be restored. It was observed that plastic deformation immediately after quenching significantly decreased the artificial aging time to achieve the peak hardness. Besides the conventional solution heat treatment process, an alternative retrogression and re-aging procedure was identified for the alloy EN AW-7020. While the heat treatment temperature can be reduced as compared to the conventional solution heat treatment, the formability and hardenability are equally good. In contrast, no such alternative process could be identified for the alloy EN AW-7075.

The effect of subsequent heat treatment on the evolution behavior of second phase particles and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

In this work, the influence of subsequent heat treatment on the evolution behavior of Laves phase, δ phase and carbides, and mechanical properties were investigated systematically for the Inconel 718 superalloy manufactured by selective laser melting (SLM). Two different subsequent heat treatment schemes were employed for SLM manufactured Inconel 718 superalloy in our work: 980 °C * 1 h/AC + 720 °C * 8 h/FC to 620 °C * 8 h/AC (the standard heat treatment scheme, SA980) and 1080 °C * 1 h/AC + 720 °C * 8 h/FC to 620 °C * 8 h/AC (the optimized heat treatment scheme, SA1080). The results show that the δ phase can nucleate around the residual Laves phase, and then the composite phase particles are formed at the subgrain boundaries during SA980 heat treatment of SLM manufactured Inconel 718. Moreover, the entangled dislocations around these composite phase particles can promote the initiation of microcrack during the tensile process at elevated temperature, leading to premature failure. On the other hand, two types of carbides were found to exist in the SA1080 heat-treated samples: the nanoscale TiC particles along subgrain boundaries originally formed during the SLM process, and the large-size NbC particles along the grain boundaries formed during the solution heat treatment process. The heat treatment schemes of SA1080 can achieve excellent combination of strength and elongation at room temperature and elevated temperature, which is more suitable for the subsequent heat treatment of SLM manufactured IN718.

Study on Dissolution of Al2Cu in Al-4.3Cu and A205 Cast Alloys

Evolution of microstructure in a binary Al-Cu system (Al-4.3Cu) and a commercially alloyed Al-Cu system (A205) during solution heat treatment was investigated using optical microscopy (OM), scanning electron microscopy (SEM), wavelength-dispersive X-ray spectroscopy (WDS), and differential scanning calorimetry (DSC). The diversified coarseness of the microstructure was initiated by controlling the solidification rate. Different solution treatment temperatures were applied to identify a proper solutioning temperature. The larger microstructural scale required an increased solutioning temperature and prolonged holding time to obtain homogenized solutes in the α-Al matrix. The diffusion of Cu primarily controlled the solution heat treatment process. A diffusion-based model was applied and calibrated to determine the dissolution rate of an Al2Cu particle in the matrix. The model operates on a similar time scale with the experimental results for the Al-4.3Cu and A205 alloys with various microstructural scales, different chemical compositions, and at different solution treatment temperatures. Three-dimensional (3D) reconstructed images from SEM images and energy dispersive spectroscopy (EDS) map of elements showed that TiB2 particles shield the Cu-rich phases in the boundaries of α-Al grains, presumably acting as a physical barrier to the diffusion of Cu solutes toward α-Al grains. The model also suggests that the effective diffusion coefficient of Cu in Al, in the presence of TiB2 particles, reduced by a factor of 2.0–2.5 in the A205 alloy compared with the binary Al-Cu alloy.

Effect of Transition Metals Addition on Tensile Properties of Al–Si–Cu-Based Alloys at 25 °C and 250 °C: Role of Heat Treatment

The tensile data showed that strength and percent elongation of the Zr-containing 354 (Al–9%Si–1.8%Cu–0.5%Mg) alloys increased in the one-step solution heat-treated condition compared to the as-cast case. The multi-step solution heat treatment displayed higher tensile properties than those achieved with single-step solution heat treatment. The use of the T6 treatment, incorporating the multiple solution heat treatment, allows for maximum dissolution of the copper phases in the multiple stages of solution treatment, resulting in the greatest improvement in the alloy strength. The best tensile properties of alloys tested at room temperature after stabilization at 250 °C for 200 h are obtained with the T6 heat treatment. The addition of Zr, Ni, and Mn to Al–Si alloys improves the high-temperature tensile properties of the 354 alloy. Alloys containing 2%Ni or 0.75%Mn perform better in case of high-temperature conditions, with 1-h stabilization at 250 °C. After 200-h stabilization at 250 °C, the strength of the T6-treated alloys—regardless of the type of solution heat treatment process, is reduced considerably, while the ductility is increased, with base alloy showing the highest percent elongation, ~ 19%. The reduction in strength may be attributed to the alloy softening which occurs after such long stabilization time at the high testing temperature (250 °C).

A study of various heating effects on the microstructure and mechanical properties of AA6082 using EBSD and CPFE

The solution heat treatment (SHT) process resolving hardening precipitates in high strength aluminium alloys is a critical step for high-efficient forming processes, such as Hot Form Quench (HFQ®). SHT largely determines the overall cycle time of a forming process. However, effects of heating process parameters, such as the heating rate and soaking time, on the microstructure and the associated mechanical properties of aluminium alloy 6082, one of the most commonly used aluminium alloys, for HFQ applications, have not been systematically investigated. The aim of this study is to explore and understand the relationships among heat treatment conditions, grain microstructure and associated mechanical properties for AA6082. A series of uniaxial tensile tests conducted under various SHT conditions revealed significant variations on mechanical behaviour characterised by stress-strain curves. To correlate these stress-strain relationship with underlying microstructure, the grain and orientation distribution of each heat-treated sample were characterised by the electron backscatter diffraction (EBSD) technique. Due to the presence of a large number of microscopic variables, such as grain size, morphology, texture, grain boundary and etc., the crystal plasticity finite element (CPFE) modelling was employed to identify the key microscopic factors which determine the differences in the observed strength and ductility for all samples. A new CPFE model integrated with local strain criterion was proposed and validated to correlate the ductility and the strength with the material microstructure. This rigorous investigation provides more insights on how microstructure (grain size and texture) affects the mechanical behaviour for AA6082, which enables to enlarge the capability of HFQ for industrial applications.