Solution Heat Treatment Temperature Research Articles

Effects of residual Laves phase on microstructural evolution and mechanical properties of wire arc additive manufactured GH4169 Ni-based superalloy

The GH4169 Ni-based superalloy is prepared by wire arc additive manufacturing and the sizes and morphologies of Laves phases under different heat treatment strategies are obtained to further investigate the influence of residual Laves phases on the tensile properties of the superalloy. After the solution treated at a higher 1150 °C and followed by aging, the Laves phase is completely dissolved, with limited δ phase with varying sizes distributed at the grain boundaries. While for lower 1020 °C solid solution heat treatment temperature, the Laves phase in the sample changes from chain-like to particle-like shapes by partially dissolving, and the needle-like δ phase exists around the particle-like Laves phase. Such residual "Laves + δ" impede high-temperature tensile crack propagation, significantly enhancing plasticity. This mechanism makes the lower temperature solid solution treated sample exhibit similar tensile stress but ∼2 times of elongation when compared to the sample treated by higher solid solution.

Effect of Heat Treatment Temperature on Microstructure, Tensile Properties and δ-Precipitate Phase in Ni-based Superalloy

Here, we investigated the influence of δ-precipitate (orthorhombic D0a Ni<sub>3</sub>Nb-ordered phase) on the room- and high-temperature tensile properties in wrought nickel-based Inconel 625 superalloys subjected to solution and aging heat treatment. Typically, solution heat-treatment temperatures in these alloys affect the solid-state precipitation of δ-phase, which governs high-temperature tensile properties. While precipitation of fine D0<sub>a</sub> δ-phase is known to have beneficial effects on the mechanical properties owing to the retardation of grain coarsening, Widmanstätten δ precipitation plays a deleterious influence on the fracture toughness, tensile ductility, and fatigue resistance. Therefore, to enhance the mechanical properties of this alloy series, it is key to generate a high number density of fine D0<sub>a</sub> δ precipitate by adjusting solid solution treatment temperatures. In this study, solution heat treatments were conducted above and below δ-phase solvus temperatures. By applying solution heat treatment at 900°C and 970°C, this alloy was confirmed to have a Widmanstätten δ phase and is composed similarly to the annealed microstructure. This Widmanstätten δ precipitate was densely distributed at both intergranular and intragranular grains. On the other hand, when solution treatment was applied at 1040 and 1100°C, more coarse particles (approximately 30 μm) with a significant reduction of Widmanstätten type δ phase were obtained. We found that grain size and Widmanstätten δ-phases have an important role in the high-temperature tensile properties of Inconel 625 superalloy series.

Study of natural aging behavior of Al-0.4Mg-1.0Si alloy with the addition of Sn at different solution heat treatment temperatures

In this paper, the combined effect of Sn addition and solution treatment temperature on natural aging (NA) hardness behavior and microstructure of Al-0.4Mg-1.0Si alloy were investigated by hardness test, scanning electron microscope (SEM) and scanning transmission electron microscope (STEM). The evolutions of clusters characterized by three-dimensional atom probe (3DAP) during initials stages of NA are also investigated based on the slow in formation of clusters due to Sn addition. The results shown that a Sn-rich particles with round shape retained in Al matrix after quenching treatment when the added Sn content exceeds it limit solubility, which will reduce the Mg content of the designed alloy. The suppression of NA can be enhanced with the increase in the adding Sn content and solution treatment temperature, which is strongly related to the delay of the segregation of Mg and Si to form clusters due to more trapping vacancies by Sn atoms. The addition of Sn also revealed that the segregation of Si during NA is earlier than that of Mg atoms. The Si-rich clusters are formed preferentially during initial stage of NA, and Mg–Si co-clusters are formed after long period of NA. The Mg/Si ratio and average size of Sn-containing clusters in the 0.04%Sn and 0.1%Sn alloy are obviously higher than that of Sn-free clusters regardless of the 1 day NA or 14 days NA as more Mg atoms are dragged into Sn-containing clusters due to strong interaction between Sn and Mg atoms.

Biocompatible, robust, waterproof and breathable PDMS-based PU fibrous membranes for potential application in wound dressing

Wound dressings, an effective tool for repairing injured skin and protecting it from secondary damage, have been widely manufactured. However, the design of wound dressings with waterproofness, breathability, mechanical robustness, and excellent biocompatibility remains a challenge due to the imbalance between the multiple desirable properties. Herein, a strategy is proposed to fabricate biocompatible membranes via a facile one-step electrospinning method. Polydimethylsiloxane-based polyurethane is effectively prepared to form durable hydrophobic surfaces, resulting in a high degree of hydrophobicity (141.0° water contact angle). The porous structure is enhanced by adjusting the solution concentration and heat treatment temperature, resulting in an optimal water vapor transmission rate of 8.2 kg·m−2·h−1. Additionally, the membrane exhibits a hydrostatic pressure of 52.3 kPa, which is approximately 14.1 times greater than that of PU fibrous membrane, and an enhanced tensile strength of 6.60 MPa. Moreover, the membrane can be utilized in a wide temperature range from − 123 °C to 160 °C due to its low glass transition temperature and exceptional thermal stability. Significantly, both in vitro and in vivo studies confirmed the remarkable biocompatibility and minimal toxicity to normal cells and mice skin. Our work presents a new approach to designing waterproof and breathable biomaterials with high mechanical strength, thereby enhancing their performance and functionality in the biomedical field, particularly in wound dressing applications.

Effect of Process Condition and Test Environment on Tensile Properties in Cold-Rolled Al-Cu-Mg Alloys

Severe plastic deformation processing and subsequent aging treatment have been known to be effective for achieving higher strength than the conventional aging treatment in aluminum alloys. This study prepared the Al-Cu-Mg-based alloy sample, Al-5.3Cu-2.8Mg (mass%). The alloys were solution treated at 480, 495 and 505°C, and cold-rolled by 90%. The effect of process condition and test environment on tensile properties in cold-rolled Al-Cu-Mg alloys was investigated. Results confirm that strength and ductility were improved with increasing the solution heat treatment temperature regardless of test environment. 0.2% proof stress and ultimate tensile strength were higher than aging treatment specimens, but elongation to failure was lower than aged one. Hydrogen embrittlement susceptibility increased with increasing solution treatment temperature. Ductile fracture with many dimples is observed in both cold-rolled and aged specimens. Second-phase particles were observed at the bottom of the dimples. There was no significant difference in fracture surface between the different test environments.

Microstructural Evolution and Mechanical Properties of a Ni-Based Alloy with High Boron Content for the Pre-Sintered Preform (PSP) Application

The pre-sintered preform (PSP) is an advanced technology for repairing the Ni-based superalloy blade in a turbine. In general, boron is added to the Ni-based superalloys in small quantities (<0.1 wt.%) to increase boundary strength and cohesivity. Despite this, the effect of high B content (>1.0 wt.%) on the microstructure evolution and mechanical properties in Ni-based superalloys for the PSP application is rarely studied. The variety, composition and evolution of the precipitates during solution heat treatment in the alloy with high B content were determined by EBSD, EPMA and SEM. The results indicate that Cr, W and Mo-rich M5B3 type borides precipitate from the matrix and its area fraction reaches up to about 8%. The area fraction of boride decreases with the prolonging of solution time and the increase of temperature higher than 1120 °C. The borides nearly disappear after solution treatment at 1160 °C for 2 h. The redissolution of boride and eutectic results in the formation of B-rich area with low incipient melting (about 1189 °C). It can bond metallurgically with the blade under the melting point of the blade, which decreases the precipitation of harmful phases of the blade after PSP repairing. The microhardness within the grain in the PSP work-blank first decreases (lower than 1160 °C) and then increases (higher than 1185 °C) with the increase of solution heat treatment temperature due to the dissolving and precipitation of borides. The tensile strength of the combination of PSP work-blank and Mar-M247 matrix at room temperature after solution treatment is related to the area fraction of boride, incipient melting and the cohesion between PSP work-blank and Mar-M247 matrix.

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.

An indirect hot form and Quench (HFQ) for manufacturing components of aluminum alloy sheets and comparison with direct HFQ

The process of Hot Form and Quench of aluminum alloys, called Direct HFQ®, has been developed and applied to manufacture high-strength panel components, in which aluminum alloy sheet is heated to solution heat treatment temperature, quickly transferred to cold press dies, simultaneously formed and quenched, and subsequently artificially aged. For Direct HFQ, however, forming occurs at high temperatures, which results in high workpiece/die friction and wear, and hence high tooling and maintenance costs. In the present study, a novel Indirect HFQ for aluminum alloys has been proposed, in which alloy sheet in the O temper is formed at room temperature, then heated to solution heat treatment temperature, and quickly transferred to cold press dies for shape calibration and quenching, followed by artificial aging. In order to compare Indirect HFQ with Direct HFQ, AA6082 sheet specimens have been deformed uniaxially using the two HFQ techniques to a given strain or fracture. Mechanical properties of the deformed specimens have been measured, and differences in mechanical properties after the two HFQ processes have been quantified. Their microstructures have also been characterized to explain those differences. In addition, both HFQ techniques have been applied to form a B-pillar sectional component. It has been found that grain growth occurs in alloy deformed uniaxially to a strain higher than or equal to 10% during Indirect HFQ process, and the degree of grain growth decreases with increasing deformation. The grain growth during Indirect HFQ leads to a lower yield strength (up to ∼8%) and tensile strength (up to ∼12%) than that of the alloy processed using Direct HFQ. In addition, the alloy has a lower ductility and formability during Indirect HFQ than Direct HFQ.

Effect of Solution Heat Treatment (Temperature and Time) on Microstructure and Properties of Al–Cu–Mg Alloy

Effect of Solution Heat Treatment (Temperature and Time) on Microstructure and Properties of Al–Cu–Mg Alloy

The Evolution of Abnormal Grains during the Heating Stage of a Post-Weld Solution Treatment in a Friction-Stir-Welded 2519 Aluminium Alloy

This work presents an in-depth investigation of the early stages of abnormal grain growth (AGG) in a friction-stir-welded (FSWed) 2519-T820 aluminium alloy. Microstructural evolutions, which occurred during the heating stage of a solution heat treatment (SHT), were studied. It was found that the welded materials underwent a complex sequence of precipitation phenomena, which eventually led to AGG. The evolution of precipitates was found to be heavily dependent on the FSW temperature condition. In a weld produced with a low-heat input, a significant portion of the precipitates were retained in the stir zone after FSW and then underwent coarsening and a subsequent dissolution during the annealing that followed. This led to a reduction in precipitation-pinning forces and thus promoted rapid grain coarsening. In a weld produced with a high-heat input, the initial precipitates were completely dissolved during the FSW, owing to the higher temperature, and then partially re-precipitated during the heating stage of the post-weld heat treatment. Due to the fine-grain structure of the stir zone, re-precipitation typically occurred at grain boundaries, thus promoting significant thermal stability. However, at temperatures approaching the SHT temperature, the new precipitates coarsened and then dissolved, resulting in AGG.

Effect of solution heat treatment on the microstructure and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam

The effect of various solution heat treatment temperatures (i.e., 1120, 1160, 1200 and 1240 °C) on the microstructure, grain morphology and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) was investigated. Microstructural analyses showed that the high-temperature gradient and rapid solidification of the PBF-LB processing caused different resulting microstructures compared to conventionally produced counterparts. The melt pool morphologies and laser scanning paths were examined in the as-fabricated samples in the XZ- and XY-planes, respectively. After the application of solution heat treatment at 1120 °C, the as-fabricated PBF-LB initial microstructure was still apparent. For solution heat treatments of 1200 °C and above, the melt pool and scanning path morphologies disappeared and converted into a mixture of columnar grains in the XZ-plane and equiaxed grains in the XY-plane. On the other hand, large equiaxed grains were observed when the samples were solutionized at 1240 °C. Additionally, γ′ phase precipitated within the matrix after all solution heat treatment conditions, which led to increase in the microhardness values. According to electron backscatter diffraction (EBSD) analyses, both as-fabricated and solution heat-treated samples had intense texture with {001} plane normal parallel to the building direction. The first recrystallized grains began to appear when the samples were subjected to the solution heat treatment at 1160 °C and the fraction of the recrystallized grains increased with increasing temperature, as supported by kernel average misorientation (KAM) and grain spread orientation (GOS) analyses.

Mechanical performance and failure modes of self-piercing riveted joints between AA6061 and solution-treated TC4 alloy

TC4 titanium alloy and AA6061 aluminum alloy are widely used in the transportation industry because of their excellent mechanical properties and lightweight. In this work, the TC4 titanium alloy was solution heat treated between 800 °C and 990 °C for 1 h, and water cooled to room temperature. The riveting and tensile tests at room temperature were conducted to evaluate the joint performance. The tensile strength and failure morphology were used to discuss the mechanical performance of joints. Solution heat treatment significantly improves the elongation, mechanical performance, and hardness of TC4 titanium alloy. Compared with the as-received material, the elongation of the treated TC4 titanium alloy is increased by 13% at the solution temperature of 900 °C, the tensile strength was added by 175 MPa at 930 °C, and the hardness was significantly increased. The optimal performance of the TC4 titanium alloy can be obtained at 930 °C. The tensile strength of the joint with the TC4 alloy solution heat treated at 930 °C is the highest of all joints. When the TC4 alloy was solution treated between 800 °C and 850 °C, the rivets were pulled from the AA6061. While at 900 °C and 930 °C, the AA6061 sheet was broken at the rivet. At 960 °C and 990 °C, the TC4 sheet was broken near the rivet. The crack size of TC4 titanium alloy gradually decreases from the rivet outward, and the crack spreads around the rivet. Severe friction can be found, which causes the peeling of the lower plate AA6061 alloy. The breaks of TC4 alloys were the plastic broken. The failure morphology of the TC4 alloy sheet is different under different solution heat treatment temperatures.

Clustering and Precipitation during Early-Stage Artificial Aging of Al–Si–Mg(–Cu) Foundry Alloys

High-Si aluminum foundry alloys are an important material class for products with complex 3D geometries where casting is the most suitable production method. With Mg and/or Cu additions, these alloys gain strength upon heat treatment due to the formation of nanoprecipitates. These precipitated phases are of the same kind as in the wrought Al–Mg–Si(–Cu) alloys having much lower Si contents, which have been the subject of a high number of studies. Some of these studies indicate that atomic clusters formed during storage at room temperature have a strong effect on the phases that evolve during artificial aging. In this work, foundry alloys containing Si, Mg, and Cu are investigated. Room-temperature storage is found to have a great influence on kinetics during early aging. Cu additions accelerate the formation of hardening precipitates during early aging, but 1 month of room-temperature storage negates the positive effect of Cu. The maximum achievable strength is found to be limited mainly by the solubility limits of Si and Mg at the solution heat treatment temperature. With insights derived from transmission electron microscopy and atom probe tomography results, this study contributes to the understanding of the solute balance and early aging kinetics and how wrought and foundry alloys differ in these respects.

Dependency of mechanical properties on artificial aging conditions for EN AW 6082 aluminum alloy

Aluminum 6xxx series alloys attract attention owing to their decent strength, formability and corrosion characteristics. Mechanical properties of these alloys can be altered via precipitation hardening by applying an aging treatment known as artificial aging (AA). This investigation was focused on the behavior of mechanical properties of EN AW 6082 alloy for various aging conditions. Mechanical property response for different heat treatment procedures were analyzed together with DSC results and TEM micrographs. Solution heat treatment (SHT) temperature was found to affect the obtained yield strengths after AA considerably and higher SHT temperatures lead to higher yield strength for same artificial aging condition. It was also shown that yield strength values obtained after 480 min—180 °C artificial aging can be surpassed in shorter times at higher artificial aging temperatures. Aging times as short as 60 min may be employed using temperatures above 200 °C to obtain higher strength than 480 min—180 °C aging. Linear relationships between Vickers hardness and mechanical strengths were suggested for the complete data of the study. Negative effects of over-aging on ductility were presented and β′′ precipitates which are responsible for hardening during aging were presented using TEM micrographs. Additionally, high cycle fatigue tests were conducted for AA procedures 480 min—180 °C and 240 min—200 °C and similar fatigue strengths were reported.

Role of microstructure heterogeneity on deformation behaviour in additive manufactured Ti-6Al-4V

The influence of two different bi-lamellar microstructures, with varied volume fractions of primary alpha lamellae (αp) and secondary alpha lamellae (αs), on the mechanical performance of laser powder bed fusion fabricated Ti-6Al-4V has been investigated. A low and high αp volume fraction variant was created by different solution heat treatment temperatures. Scanning transmission electron microscopy (STEM) was performed on both materials to give a comprehensive assessment of the local microstructure and element partitioning effects. Deformation experiments, combined with high resolution digital image correlation (HRDIC), enabled a detailed comparison of 2D slip patterns at progressive strain increments during tensile loading, with the underlying microstructure collected using electron backscattering diffraction based grain orientation mapping. In both microstrural variants, shear strain was mainly observed in the coarse αp lamellae, suggesting that the constituent was softer than the fine αs regions. This strength difference is not attributed to potential different levels of Al-based solid solution strengthening as a result of element partitioning. Instead, the strength difference was attributed to the fine β ligaments formed in-between the αs during ageing. The low αp volume fraction variant, i.e. high-volume fraction of αs, displayed a significant increase in yield strength compared to the high αp volume fraction variant without compromising ductility through increased heterogeneous plasticity and an enhanced strain hardening rate.

Influence of Two‐Step Heat Treatments on Microstructure and Mechanical Properties of a β‐Solidifying Titanium Aluminide Alloy Fabricated via Electron Beam Powder Bed Fusion

Additive manufacturing technologies, particularly electron beam powder bed fusion (PBF‐EB/M), are becoming increasingly important for the processing of intermetallic titanium aluminides. This study presents the effects of hot isostatic pressing (HIP) and subsequent two‐step heat treatments on the microstructure and mechanical properties of the TNM‐B1 alloy (Ti–43.5Al–4Nb–1Mo–0.1B) fabricated via PBF‐EB/M. Adequate solution heat treatment temperatures allow the adjustment of fully lamellar (FL) and nearly lamellar (NL‐β) microstructures. The specimens are characterized by optical microscopy and scanning electron microscopy (SEM), X‐ray computed tomography (CT), X‐ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical properties at ambient temperatures are evaluated via tensile testing and subsequent fractography. While lack‐of‐fusion defects are the main causes of failure in the as‐built condition, the mechanical properties in the heat‐treated conditions are predominantly controlled by the microstructure. The highest ultimate tensile strength is achieved after HIP due to the elimination of lack‐of‐fusion defects. The results reveal challenges originating from the PBF‐EB/M process, for example, local variations in chemical composition due to aluminum evaporation, which in turn affect the microstructures after heat treatment. For designing suitable heat treatment strategies, particular attention should therefore be paid to the microstructural characteristics associated with additive manufacturing.

Influence of Heat Treatment on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy Prepared by Selective Laser Melting (SLM).

From previous studies, it is known that the dissolution of β-Mg17Al12 at high temperature and the increase of densities at high pressure after hot isostatic pressing (HIP) are the two main reasons for significant improvement in the ductility of AZ61 magnesium alloy prepared by SLM. However, the mechanism of dissolution of β-Mg17Al12 in SLMed AZ61 magnesium alloy at high temperature is not clear. To illustrate the mechanism of the effect of β-Mg17Al12 dissolution on the ductility of SLMed AZ61 Mg alloy, the effect of solid solution heat treatment (T4) on the microstructure and mechanical properties of SLMed AZ61 was investigated and the kinetic model of β-Mg17Al12 dissolution of SLMed AZ61 magnesium alloy was established. According to the results, there is no significant change in the dissolution of the β-Mg17Al12 with an increase of temperature and time when the T4 temperature is lower than 410 °C. At the optimum solution heat treatment temperature of 410 °C, the dissolution rate is accelerated and the β-Mg17Al12 is completely dissolved after 2 h. In addition, the dissolution rate of β-Mg17Al12 decreases with the increase of dissolution time. The strength of SLMed AZ61 magnesium alloy decreases and the ductility increases as the T4 temperature increases. The strength of the specimens is reduced by grain coarsening (29.2 ± 3.7 μm), but the elongation is increased by 90% compared to SLMed AZ61, due to the effect of β-Mg17Al12 dissolution.

Stress Relaxation during Artificial Aging of an AlSi7Cu0.5Mg Cast Alloy

After casting and solidification, Al cast cylinder heads undergo a sequence of heat treatments to achieve the desired material properties. This sequence comprises solution heat treatment (SHT), quenching, and artificial aging. Internal stresses are formed due to temperature gradients in the complex geometry of the cylinder heads during quenching from the SHT temperature to room temperature. Especially high tensile stresses can produce damage during service. However, part of these internal stresses relaxes during the aging treatment. This work aims to systematically measure the relaxation of the stresses, as well as to phenomenologically model the amount and rate of relaxation. Cast specimens of AlSi7Cu0.5Mg are heat-treated in a furnace before relaxation in a creep testing machine. SHT and SHT plus aging at 180, 200, and 230 °C for 0 h, 0.5 h, 1 h, 4 h, and 6 h are carried out before testing. The relaxation of the stress at constant temperature and strain over 5 h is recorded at three different testing temperatures (180 °C, 200 °C, and 230 °C). The relaxation process is strongly dependent on the testing temperature: at 180 °C and 200 °C the equilibrium stress was already reached after around 1 h, and at 230 °C the equilibrium was reached after 3.5 h. The initial stress values do not influence the relaxation rate. A phenomenological relaxation model is developed to calculate the stress decrement over time and the equilibrium stress in the AlSi7Cu0.5Mg-alloy. The model allows for calculating the levels of residual stress at any time during artificial aging as a function of the thermal history of the alloy, the relaxation temperature, and the initial stress level. Complete relaxation of the initial stress is not reached within 5 h.

Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy

In order to meet the continuously increasing environmental concerns, automotive lightweight concepts of replacing steels with high strength aluminium alloys are one promising solution. Therefore, complex automotive structural components manufactured with new processes like rapid gas-based hot sheet metal forming can become a key factor from a forming technology point of view. A product and process development phase, which is mainly assisted by numerical simulations, mandates knowledge of the material forming limits under the process conditions. The aim of this work is to determine the FLD of a 6xxx precipitation-hardening aluminium alloy within the solution heat treatment temperature range under gas-based hot forming process conditions. For this purpose, a hydraulic double-layered bulge test, as introduced by Banabic, is used as the basis and a high-temperature test setup as well as a characterization methodology are established. FE simulations are utilized to optimize the specimen geometries aiming at specific strain paths. Experiments are conducted with the optimized specimen geometries and the high-temperature FLD is extracted. The FLD is further used in simulations for process parameter identification for failure-free gas-based hot forming of a laboratory scale benchmark component. Experimental validations showed the reliability of the methodology and the determined FLD for failure prediction in the novel forming process.

Investigation of optimal solid solution heat treatment temperature and artificial aging time of Al7075 sheet

Investigation of optimal solid solution heat treatment temperature and artificial aging time of Al7075 sheet