Higher Solution Temperature Research Articles

Effects of surfactants, ion valency and solution temperature on PFAS rejection in commercial reverse osmosis (RO) and nanofiltration (NF) processes

Per- and polyfluoroalkyl substances (PFAS) have garnered attention as a pressing environmental issue due to their enduring presence and suspected adverse health effects. This study assessed the rejection or removal efficacy of PFAS by commercial reverse osmosis (RO) and nanofiltration (NF) membranes and examined the impacts of surfactants, ion valency and solution temperature that are inadequately explored. The results reveal that the presence of cationic surfactants such as cetyltrimethylammonium bromide (CTAB) increased the rejection of two selected PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA), by binding with negatively charged PFAS and preventing them from passing through membrane pores via size exclusion, whereas the presence of anionic surfactants such as sodium dodecyl sulfate (SDS) increased the PFAS rejection because the increased electrostatic repulsion prevented PFAS from approaching and adsorbing onto the membrane surface. Moreover, aqueous ions (e.g., Al3+ and PO43−) with higher ion valency enabled higher rejection of PFOA and PFBA through increased effective molecular size and increased electronegativity. Finally, only high solution temperature at 45 °C significantly reduced PFAS rejection efficiency because of the thermally expanded membrane pores and thus the increased leakage of PFAS. Overall, this research provides valuable insights into the various factors impacting PFAS rejection in commercial RO and NF processes. These findings are crucial for developing efficient PFAS removal methods and optimizing existing treatment systems, thereby contributing significantly to the ongoing efforts to combat PFAS contamination.

Waste newspaper as cellulose resource of activated carbon by sodium salts for methylene blue and congo red removal

The work was aimed at evaluating the adsorptive properties of waste newspaper (WN) activated carbons chemically produced using sodium salts for methylene blue (MB) and congo red (CR) removal. The activated carbons, designated as AC1, AC2, AC3 and AC4 were prepared through impregnation with NaH2PO4, Na2CO3, NaCl and NaOH, respectively and activation at 500 °C for 1 h. The activated carbons were characterized for surface chemistry, thermal stability, specific area, morphology and composition. The AC1 with a surface area of 917 m2/g exhibits a greater MB capacity of 651 mg/g. Meanwhile, a greater CR capacity was recorded by AC2 at 299 mg/g. The pseudo-second order model fitted well with the kinetic data, while the equilibrium data could be described by Langmuir model. The thermodynamic parameters, i.e.., positive ΔH°, negative ΔG° and positive ΔS° suggest that the adsorption of dyes is endothermic, spontaneous and feasible at high solution temperature. To conclude, WN is a potential cellulose source for producing activated carbon, while NaH2PO4 activation could be employed to convert WN into activated carbon for effective dye wastewater treatment.

Sustainable, super-stable thermochromic material by coupling hydroxypropyl cellulose and sodium carboxymethyl cellulose

Hydroxypropyl cellulose (HPC) is a green thermochromic material in energy-saving buildings, anti-counterfeiting, and data security fields. However, the high lower critical solution temperature (LCST) of HPC, around 42 °C (higher than the human thermal comfort temperature), limits its thermochromic sensitivity, poor stability, and short lifespan. Herein, we developed a durable, high-performance cellulose-based thermochromic composite with a lower LCST and easy preparation capability by combining HPC with sodium carboxymethyl cellulose (CMC). In such thermochromic cellulose, CMC constructs a hydrophilic skeleton to enable uniform dispersion of HPC, and functions as a stronger competitor to attract the water molecules compared to HPC, both of which trigger high thermochromic sensitivity and low LCST (just 32.5 °C) of our CMC/HPC. In addition, CMC/HPC shows superior stability, such as 100-day working capability and 60-time recyclability. This advancement marks a significant step forward in creating sustainable, efficient thermochromic materials, offering new opportunities for energy conservation in the building.

Influence mechanism of solution temperature on microstructure evolution and tensile properties of Ti microalloyed high strength steel CGLC700

The influence mechanism of solution temperature on the strength and toughness of Ti microalloyed steel CGLC700 was studied. The microstructure changes of Ti microalloyed steel were observed by micro-electron microscopy, and the mechanical properties were evaluated by tensile test. The appropriate solution temperature can promote the solid solution of Ti atoms and the formation of small-sized TiN, TiC and other particles, hinder the movement of dislocations, and improve the tensile properties of steel. When the solution temperature is 1240 °C (2#), the grain size of steel is the lowest, the proportion of high angle grain boundary is the highest, and the tensile properties of steel are the best. Ti microalloyed steels increased tensile strength by 4.12%, yield strength by 2.85% and elongation by 28.4%. Too low or too high solid solution temperatures weaken the strengthening effect of the microalloying elements and led to a reduction in the tensile properties of the steel. This can be attributed to the low solid solution of Ti at low solid solution temperatures and the growth of second phase particles and inclusions at too high solid solution temperatures. This study provides a theoretical basis for optimizing the heat treatment process of Ti microalloyed steel.

Protection of bovine serum albumin through encapsulation in hybrid vesicles

This study focuses on hybrid vesicles (HVs) formed through co-assembly of soy phosphatidylcholine (SPC) and a triblock copolymer (F127). After elucidating the superior stability of HVs over the assemblies of neat SPC and F127, these were encapsulated with bovine serum albumin (BSA), as model a thermolabile protein. Characterizations were performed using dynamic light scattering (DLS), electron microscopy, circular dichroism and high-sensitivity differential scanning calorimetry. The size of HVs increased slightly at higher proportion of F127 and upon encapsulation of BSA. In spite of this, vesicles remained spherical and displayed a smooth surface. They showed superior dilution stability in comparison to neat copolymer micelles and phospholipid vesicles. Their stability can be ascribed to hydrophobic association between the phospholipid and copolymer, and manifested into increase in phase transition temperature of the former. We found that HVs could protect BSA from denaturation and unfolding when challenged by high solution temperature, pH changes and salt incorporation.

Valorization of cardboard waste adsorbents for efficient malachite green removal – equilibrium, kinetics, and thermodynamics

ABSTRACT This work was aimed at evaluating the adsorptive properties of cardboard waste-based adsorbents for malachite green removal. The adsorbents were produced through hydrothermal carbonization and/or phosphoric acid activation and characterized for specific area, surface morphology, and functional groups. Batch adsorption was performed at varying concentrations, contact times, and temperatures. Results show that the activated carbon derived from cardboard waste with surface area of 196 m2/g exhibits a 134 mg/g (31.6%) adsorption capacity of malachite green. On the other hand, the cardboard hydrochar displays a peak capacity at 400 mg/g (94%) due to dye precipitation before the magnitude subsides to 47 mg/g (5.7%) at higher concentration of 820 mg/L. The equilibrium data of activated carbons could be well described by the Langmuir model, while the kinetics fitted well with the pseudo-second order model. The adsorption of malachite green is endothermic and spontaneous at high solution temperature.

Corrosion performance of carbon steel and 304 stainless steel in activated methyldiethanolamine solution using autoclave tests

This study evaluated the corrosion performance of carbon steel (CS) and 304 stainless steel (304 SS) under high temperature and pressure (inside an autoclave) in a CO2-saturated solution of activated methyldiethanolamine (aMDEA). The aim was to determine the effect of temperature, presence of chloride ions, degradation of the aMDEA and amount of dissolved oxygen on the corrosion resistance of these materials. The results indicated that raising the temperature between 50 and 120°C led to a higher corrosion rate of both CS and 304 SS. However, the corrosion rate of 304 SS decreased and remained stable at higher temperatures as the corrosion reaction became mass-controlled. Oxygen loading results in the passivation of both CS and 304 SS. The amine degradation products were found to accelerate the corrosion rate of CS at 50°C due to a chelation effect of iron ions, and also increase the corrosion rate of 304 SS at 120°C by causing the passive film rupture. The SCC test on U-shaped 304 SS samples showed transversal microcracks with a depth of more than 25 µm after 2 months of immersion in an autoclave containing CO2-saturated aMDEA at 120°C, which confirmed the SCC risk of 304 SS.

Effects of solution temperatures on microstructures and mechanical properties of B4C/7A04Al composites: A comparison study with 7A04Al alloys

To prepare particle-reinforced aluminum matrix composites with ultra-high strength, high-strength 7xxx Al alloys are commonly employed as matrices. Heat treatment plays a crucial role in enhancing the mechanical properties of the alloys and their composites, but the influence of solution temperatures on composites based on 7xxxAl alloys remains unexplored. In this study, the effects of solution temperatures on the microstructures and mechanical properties of B4C/7A04Al composites fabricated via powder metallurgy (PM) technology were investigated, as well as those of 7A04Al alloys for comparison. Before solution treatments, the prominent second phases in the composite were MgZn2 phases, while those in the 7A04Al alloy consisted of MgZn2 and Al2CuMg phases. At lower solution temperature (420 °C), MgZn2 phases dissolved completely, whereas Al2CuMg phases persisted. Al2CuMg phases dissolved at 450 °C, and thus the 7A04Al alloy obtained the optimum strength and elongation. Further elevating the solution temperature caused abnormal grain growth (AGG) in the 7A04Al alloy, leading to a deterioration of strength and plasticity. In contrast, at various solution temperatures, the composite exhibited stability in grain size, which could be attributed to the pinning effects of B4C particles and Mg(Al)B2 phases, the reaction products between the boron impurity and the Al matrix. However, at higher solution temperatures (510 °C and 600 °C), the segregation of Mg and O around B4C particles was aggravated, and thus the elongation of the composite deteriorated. Interestingly, the strength remained relatively unaffected due to the strengthening effects of Mg(Al)B2 phases. The results indicate that the composite exhibited a broad range of solution temperature with comparable strength and elongation across a temperature range of 420 °C–470 °C. But for the 7A04Al alloy, the optimal solution temperature is 450 °C.

An Investigation into the Mechanism of Alkaline Extraction-Isoelectric Point Precipitation (AE-IEP) of High-Thiol Plant Proteins

Hempseed protein isolate (HPI) has drawn significant attention as a promising source of plant-based protein due to its high nutritional value. The poor functionality (e.g., solubility and emulsifying properties) of HPI has impeded its food application for years. This study provides important new information on hempseed protein extraction, which may provide further insights into the extraction of other high-thiol-based plant proteins to make valuable plant-based products with improved functional properties. In this study, HPI was produced from hempseed meals using the AE-IEP method. The underlying mechanisms and extraction kinetics were investigated under different experimental conditions (pH 9.0–12.0, temperature 24–70 °C, and time 0–120 min). The results suggested that disulphide bond formation is an inevitable side reaction during hempseed protein extraction and that the protein yield and the free -SH content can be influenced by different extraction conditions. A high solution pH and temperature, and long extraction time result in increased protein yield but incur the formation of more intermolecular disulphide bonds, which might be the reason for the poor functionality of the HPI. For instance, it was particularly observable that the protein solubility of HPI products reduced when the extraction pH was increased. The emulsifying properties and surface tension data demonstrated that the functionality of the extracted hempseed protein was significantly reduced at longer extraction times. A response surface methodology (RSM) optimization model was used to determine the conditions that could maximise HPI functionality. However, a three-fold reduction in protein yield must be sacrificed to obtain the protein with this high functionality.

Synthesis of co-pyrolyzed biochar using red mud and peanut shell for removing phosphate from pickling wastewater: Performance and mechanism

Iron (Fe)/iron oxide-modified biochar has practicable adsorption capability for phosphorus (P), but it is expensive. In this study, we synthesized novel low-cost and eco-friendly adsorbents co-pyrolyzed biochars using Fe-rich red mud (RM) and peanut shell (PS) wastes via a one-step pyrolysis process for removing P from pickling wastewater. The preparation conditions (heating rate, pyrolysis temperature, and feedstock ratio) and P adsorption behaviors were systematically investigated. In addition, a series of characterization and approximate site energy distribution (ASED) analyses were conducted to understand the P adsorption mechanisms. The magnetic biochar (BR7P3) with m (RM):m (PS) of 7:3 prepared at 900°C and 10 °C/min had a high surface area (164.43 m2/g) and different abundant ions (including Fe3+, and Al3+). In addition, BR7P3 exhibited the best P removal capability (142.6 mg/g). The Fe2O3 from RM was successfully reduced to Fe0, which was easily oxidized as Fe3+ to precipitate with H2PO4−. The electrostatic effect, Fe–O–P bonding, and surface precipitation were the main mechanisms of P removal. ASED analyses revealed that high distribution frequency and solution temperature led to a high P adsorption rate of the adsorbent. Therefore, this study provides new insight into the waste-to-wealth strategy by transforming PS and RM into mineral-biomass biochar with excellent P adsorption capability and environmental adaptability.

Effect of cyclic heat treatment on abnormal grain growth in Fe-Mn-Al-based shape memory alloys with different Ni contents

Cyclic heat treatment that can continuously promote abnormal grain growth is widely used for the preparation of single‐crystal Fe‐Mn‐Al‐based shape memory alloys. However, it takes a long time to prepare large‐size Fe‐Mn‐Al‐based alloy single crystals via the reported cyclic heat treatments. Meanwhile, the long‐time cyclic heat treatment at high temperatures leads to the development of defects including oxidation and a decrease in Mn, which would deteriorate superelasticity in the Fe‐Mn‐Al‐based shape memory alloys. To shorten the fabrication time of single crystals, the effect of the cyclic heat treatment process on the abnormal grain growth in the Fe‐Mn‐Al‐based alloys with different Ni contents was systematically investigated. It is found that the abnormal grain growth of Fe‐Mn‐Al‐based alloys was not significantly affected by the Ni contents (within 2.1 at.%–6.2 at.%). In addition, the abnormal grain growth could be promoted by 1–2 °C min–1 cooling rate, high solution temperature, and multiple cycles, while it was insensitive to other processes including heating rate, dual‐phase time as well as long‐time solution treatment. These findings can guide optimizing the fabrication process of single crystals by cyclic heat treatment. Finally, the Fe41.9Mn37.8Al14.1Ni6.2 single crystal prepared by the optimized cyclic heat treatment showed a recoverable strain of about 4%.

Effect of multi-pass cooling compression and subsequent heat treatment on microstructural and mechanical evolution of TC4 alloys

Three passes of hot compression tests of hot isostatic pressed Ti-6Al-4V alloys are carried out on a Gleeble-1500D thermo-mechanical simulator with a temperature-drop of 950–900-850 °C, constant strain rate of 0.01∼1 s−1, and the height reduction from 20% to 70%. Then, the subsequent solution and aging treatments are conducted on a heat treatment furnace. The corresponding results of microstructures and mechanical properties show: In the process of multi-pass deformation, dynamic recrystallization with spheroidization of lamellar α phases are the main characteristics affecting flow behaviors. With the increasing strain, lamellar α phases gradually transform from a bimodal distribution to a single peak state perpendicular to the compression direction. The decreasing length and rising thickness of lamellar α phases in the transformation process facilitate the formation of spheroidized α phases. During the heat treatment, the proportion of spheroidized α phases increases, and the spheroidization phenomenon promotes the reduction of lamellar α phases in length and increment in thickness. Lamellar α phases mainly dominate the contribution of microhardness in the hot compression process, and the equiaxed α phases and β transformation structures are combined to influence the mechanical properties of heat-treated Ti-6Al-4V alloys. Notably, β transformation structures contribute primarily at a higher solution temperature.

Effect of Solution Treatment on Microstructure Evolution of a Powder Metallurgy Nickel Based Superalloy with Incomplete Dynamic Recrystallization Microstructure

In this paper, the powder metallurgy (P/M) Ni-based superalloy FGH4096 with an incomplete dynamic recrystallization structure was treated by a solution treatment at different temperatures, cooling methods, and holding times. The size, morphology, and distribution of grains and γ′ precipitates were characterized by an optical microscope (OM) and a scanning electron microscope (SEM). Research results showed that with the increase of solution temperature from 1060 °C to 1100 °C, the degree of recrystallization increased continuously, the distribution of grain became uniform, and a large number of annealing twins were found. At the same time, the degree of redissolution of the primary γ′ precipitates at the grain boundary increased, and the size of secondary γ′ phase reprecipitated within the grain decreased. The morphology of the secondary γ′ precipitates is mainly spherical with a single distribution under air cooling (AC), while the morphology is near-spherical, cuboids, octets, petaloid, and dendrites with a bimodal distribution under furnace cooling (FC). The size of the γ′ precipitates decreased and the volume fraction increased with the extension of holding time at a higher solution temperature (1100 °C).

Improved high-temperature fatigue performance of laser directed energy deposited Ni-based superalloy by regulating the heat treatment

The hot-section components are prone to fatigue failure due to severe working condition of high rotational speed and high cyclic load at high temperature. This study investigates the fatigue behavior of GH4169 Ni-based superalloy at 650 °C fabricated by laser directed energy deposition (L-DED) and proposes an improved high-temperature fatigue resistance by regulating the heat treatment. To this purpose, three conditions of solution and aging heat-treated fatigue specimens, namely 980STA, 980S5hDA, and 1050STA, were assessed. Results show that the fatigue resistance of the L-DEDed GH4169 with different heat treatments is mainly determined by the short crack propagation behavior, which is influenced by the combined effect of grain size and morphology. Finer grains with less texture strength of the 1050STA fatigue specimen has the longest short crack propagation life, while a cluster of large grains oriented to the 〈001〉 orientation of 980S5hDA leads to the most significant short crack propagation rate. Besides, the long fatigue crack propagation under the effect of strength and precipitates also minorly influence the fatigue resistance. The microstructure of interconnected precipitates including the needle-like δ phase and slender-stripe shaped Laves phase in 980STA and 1050STA specimens has a better hindering effect on the fatigue crack propagation than that of the discrete δ phase in 980S5hDA specimen, and the 1050STA specimen has the best strength. As a result, the 980S5hDA specimen has the worst fatigue performance, while the 1050STA specimen has the best. Compared to longer solution time, higher solution temperature can improve the fatigue resistance of the L-DEDed GH4169.

Effect of solution treatment on static recrystallization of a post-deformed GH4586 superalloy

Solution treatment was carried on a post-deformed GH4586 superalloy in the solution temperature range of 1020°C to 1100°C and solution time of 2 h and 4 h. The results showed that the static recrystallization (SRX) occurred due to the residual distortion energy caused by high temperature deformation. With increasing solution temperature from 1020°C to 1100°C, the average grain size of γ matrix firstly decreased and then increased. With increasing solution time from 2 h to 4 h, the average grain size of γ matrix gradually increased from 24.2±3.2 μm to 30.9±3.8 μm. Grain boundaries and twinning boundaries are the main nucleated site for SRX. And when solution treated at 1020°C for 2 h, carbides can also become the preferential nucleation position. In addition, by analysing the relative deviation (v/vm ) distributions of Σ3 boundaries, it could be found that the higher solution temperature would lead to the increasing fraction of coherent Σ3 boundaries and the decreasing fraction of incoherent ones. Besides, the annealing twins nucleated and grew gradually during the migration of recrystallized grain boundaries, and their length fraction increased from 10.0% to 54.9% with increasing solution temperature.

The precipitation behavior effect of δ and γ" phases on mechanical properties of laser powder bed fusion Inconel 718 alloy

The mechanical properties of additively manufactured materials were mainly influenced by the precipitations in the microstructure. In this work, Inconel 718 (IN718) superalloy was fabricated by laser powder bed fusion (LPBF) and treated by solution and dual-aging treatments. The δ and γ" phases with different sizes and morphologies have been obtained by different solution temperatures. The precipitation behavior effect of δ and γ" phases on the room temperature tensile and high temperature stress rupture properties has been investigated. The results showed that the Laves phase formed in the as-fabricated sample. After solution heat treatment, the Laves phase dissolved and transformed to δ phase. As the solution temperature increased, the needle-like δ phase gradually dissolved, while only a little short rod-like δ phase remained. During aging heat treatment, the Nb element released from dissolved δ phase was beneficial to promote the precipitation of γ" phase. The content and size of nano-scale γ" phase significantly affected the yield strength of IN718 alloy. At higher solution temperature, the γ" phase with suitable size exhibited the highest yield strength of 1283 MPa. On the other hand, δ phase had a significant impact on high temperature stress rupture properties. The stress rupture life increased from 37.2 h to 52.5 h with decreasing volume fraction of δ phase. • Revealing the precipitation behavior of δ and γ" phases in different heat treatments. • The Nb released from the dissolved δ phase was beneficial to the precipitation of the γ" phase. • Quantitatively describe the effect of phase content, size and morphology on mechanical properties.

Acrylamidevinyl acetate copolymer as a new UCST copolymer: Phase transition and aggregation behavior; an experimental and theoretical study

A high sensitive upper critical solution temperature (UCST) copolymer was synthesized through free radical copolymerization with acrylamide (AAm) and vinyl acetate (VA). The UCST behavior is due to a combination of hydrogen bonds and electrostatic potentials between copolymer chains. Turbidimetry, dynamic light scattering, and rheology studies were used to determine the phase transition and aggregation behavior. It is indicated that copolymer with 80% AAm has a phase transition temperature between 38 and 38.2 °C, which is suitable for releasing fever medicine. Also, the temperature gradient for the complete dissolution of the copolymer is 2 °C. The molecular dynamics simulations at a molecular level confirmed the experimental results and indicated that aggregation of copolymer chains below UCST temperature had increased binding energy between polymer chains. The low cytotoxicity and its desirable UCST behavior make the copolymer promising for biomedical applications in the future.

Photodegradation Behavior of Agricultural Antibiotic Oxytetracycline in Water

Due to their overuse in agriculture, antibiotics are discharged into the aquatic environment, which poses a threat to human health and aquatic organisms. The agricultural antibiotic oxytetracycline (OTC) persists in aquatic media for a long time due to its resistance to biological degradation. Photolysis is a main pathway for its degradation in the natural environment and wastewater treatment, and thus, the photolysis of OTC should be investigated. In this study, the effects of reaction conditions such as the irradiation conditions, the initial OTC concentration, and the water matrix on OTC photolysis were investigated. The most efficient degradation was observed when UV-C was used as the irradiation source (k = 0.0148 ± 0.0008 min−1), and the removal ratio increased with higher light intensity. A lower initial OTC concentration and higher solution temperature were advantageous for the degradation of OTC. The presence of humic acid or inorganic ions negatively affected the degradation rate of OTC. In addition to the effects of the reaction conditions, the degradation kinetics of OTC in actual agricultural water and the photolysis of various antibiotics such as streptomycin, validamycin A, and oxolinic acid were further studied. This work proved that various factors could decrease the photodegradation of OTC, which raises the potential risks that are associated with the persistent use of antibiotics in the water environment. Therefore, the results of the present study can help to provide an understanding of the effects of various reaction conditions on the degradation of agricultural antibiotics.

Lysozyme@Fe3O4 composite adsorbents with enhanced adsorption rates and uranium/vanadium selectivity by photothermal property

Herein, magnetic lysozyme@Fe3O4 composites have been fabricated via the amyloid-like assembly for the uranium extraction. The Fe3O4 nanoparticles and lysozyme coatings endow the composite adsorbents with magnetism for facile recovery and excellent binding affinity towards uranium, respectively. In addition, the composite adsorbents also possess outstanding photothermal properties derived from the Fe3O4 nanoparticles. The photothermal property benefits not only adsorption rates but also selectivity. The solution temperatures would increase under the sunlight, resulting in faster diffusion rates of uranyl ions and more ions could be contacted with the composite adsorbents. Moreover, the adsorption enthalpies of uranium are much higher than that of vanadium. Therefore, higher solution temperatures could generate higher uranium/vanadium selectivity.

Effect of remelting solution heat treatment on microstructure evolution of nickel-based single crystal superalloy DD5

The microstructure evolutions of nickel-based single crystal superalloy DD5 after solution treatment at different temperatures as well as heat treated with various routes were systematically investigated by differential scanning calorimeter (DSC), optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). The formation and elimination mechanisms of unfavorable incipient melting microstructure emerged during heat treatment were explored in detail. Microstructure observations reveal that a higher solution temperature can speed up the element diffusion, resulting in a more uniform element distribution. A reduced degree of lattice mismatch between γ phase and γ' phase would be obtained, which leads to an increase in the average size and content of γ' phase. However, excessively high solution temperature would cause the pre-melting occurred at the interface of γ matrix and γ' phase, causing the formation of incipient melting microstructure. The incipient melting microstructure can be eliminated by the subsequent homogenization process under the conditions that the solution temperature exceeds the solvus temperature of γ' phase. The formation course of incipient melting microstructure includes the pre-melting at the interface of γ matrix and γ' phase, the expansion of molten liquid, and the formation by the resolidification of molten liquid. The elimination of incipient melting microstructure begins with the dissolution of fine eutectic, followed by the dissolution of coarse γ' phase and the filling of pores, and eventually the dissolution of residual eutectic. Compared with standard heat treatment, remelting heat treatment can provide better homogenization effect of element for DD5 superalloy.