Increasing Solution Temperature Research Articles

Leaching of a carbonaceous gold concentrate in copper-tartrate-thiosulfate solutions

The leaching behavior of gold from a carbonaceous gold concentrate in copper-tartrate-thiosulfate solutions was studied in this paper. Experimental parameters, including temperature, initial pH, copper, tartrate, and thiosulfate concentration, were systematically investigated. The capability of leaching gold from the carbonaceous gold concentrate by copper-tartrate-thiosulfate solutions is comparable to that in cyanidation or traditional copper-ammonia-thiosulfate systems. The consumption of thiosulfate can be significantly reduced in the presence of tartrate. The mechanism of gold leaching in copper-tartrate-thiosulfate solutions is catalyzed by the mononuclear CuL2H-46− complex when the solution pH is beyond 10.5 based on thermodynamic analysis. The stability of the CuL2H-46− complex increases with an increase in the tartrate content and decreases with increasing copper and thiosulfate concentrations. A moderate increase in solution pH and temperature exhibits less effect on the consumption of thiosulfate or copper-tartrate complex, but a higher temperature may cause a sharp decline in the content of copper-tartrate complex. The recycling of the leaching solutions demonstrates that maintaining a suitable concentration of copper ions and thiosulfate and a suitable solution pH are crucial to obtain a considerable gold leaching rate.

Effects of Temperature and Sulfuric Acid and Iron (II) Concentrations on the Efficacy of Decontamination of Spent Ion-Exchange Resins Containing Hematite

The effect of H2SO4 and FeSO4 concentrations and temperature on the efficacy of decontamination of spent ion-exchange resins was estimated. The study was performed on model spent ion-exchange resins purposefully contaminated with hematite and Co-57 radionuclide. It was found that an increase in solution temperature up to 50 °C and the addition of FeSO4 increases the efficacy of decontamination of spent ion-exchange resins by 1 M and 2 M H2SO4 solutions by 1–2 orders of magnitude, whereas the decontamination factor value here is >103. Since under static conditions, the secondary adsorption of Co-57 was observed, the extra washing of ion-exchange resins by 3 M solution of NaNO3 is required. Decontamination under dynamic conditions excludes the secondary adsorption of Co-57, so that the necessity of the extra stage of washing can be skipped. Under dynamic conditions, the consumption of a solution of the composition H2SO4 (1 mol/L) + FeSO4 (0.2 mol/L) is 1.5-fold lower in comparison with the 2M solution of H2SO4 at compatible values of the decontamination factor. Such an approach enables reduction in the volume of secondary waste and the equipment corrosion due to the decrease in H2SO4 concentration.

Study of Corrosion Behavior of N'-acetyl-4-pyrrol-1-ylbenzohydrazide for Low-Carbon Steel in the Acid Environment: Experimental, Adsorption Mechanism, Surface Investigation, and DFT Studies

New corrosion inhibitors, namely N'-acetyl-4-pyrrol-1-ylbenzohydrazide (NAPB), were synthesized by the reaction of 4-pyrrol-1-ylbenzohydrazide with acetic anhydride. NAPB was characterized by FTIR and NMR spectroscopy. Weight loss measurement was used to evaluate the corrosion inhibition of Low-carbon steel in a 1 M hydrochloric acid medium. The inhibition efficiency (IE%) increased as NAPB concentration increases and decreases as the solution temperature increases. The inhibition efficiency reached 94.6 % at the optimum concentration (500 ppm) of NAPB. The scanning electron microscopy technique proved the formation of a protective layer from NAPB molecules as corrosion inhibitors on the Low-carbon steel surface. The adsorption isotherm of NAPB molecules on the surface of Low-carbon steel was confirmed to follow the Langmuir adsorption isotherm. Further, through quantum chemical calculations using density functional theory (DFT), the importance of inhibition performance and molecular structure of an inhibitor has been theoretically investigated. Both experimental and theoretical findings are consistent with one another.

Liquid Desiccant Air Conditioning System for Flat Plate Solar Collector with Nanofluids Regenerator

This paper deals with liquid desiccant air conditioning using solar flat plate collector. The problem in the use of liquid desiccant air conditioning is energy utilization for regeneration, corrosiveness and carryover. To overcome these developments of a dehumidifier for corrosion- resistant and solar regenerated are advised. A dehumidifier is made of stainless steel tubes of 316L type and stacked in aluminium fins to maintain the desiccant solution temperature. In this experiment, calcium chloride solution (CaCl2 -H2 O) is used. The solar flat plate collector is used for heating water using closed-loop of thermosiphon as regeneration. The flow rate for air is fixed at 10CFM and concentration of calcium chloride is 35% by mass is used. The inlet parameters considered are in the experiments solution volume flow rate, inlet temperature, inlet relative humidity, regeneration temperature, and desiccant solution temperature. The performance parameters are the absolute humidity reduction, outlet temperature and dehumidifier and enthalpy effectiveness. The experiments show that for a fixed Ta, inlet and RH% as solution volume flow rate increases, there is increase in absolute humidity reduction. The temperature of the dehumidified air is reduced compared to that of inlet air, if this air is passed over the pad used for the evaporating cooler. It is seen that the increase in relative humidity from 68.88% to 92.8% for the flow rate of 20 L/min and fixed inlet air temperature, increases absolute humidity reduction from 5.56 to 13.3 g/kg. The increase in solution temperature reduces the absolute humidity reduction due to solution vapor pressure increases and dehumidifier effectiveness. When the solution temperature changes from 31.5 to 34 0 C, there are reductions in the absolute humidity reduction and dehumidifier effectiveness by 34.4% and 13.04% respectively

Effect of Solution Temperature on Microstructure and Properties of Mg-2Zn-0.5Zr-1.5Dy Alloy

The purpose of this paper is to investigate the effect of solution temperature on the microstructure and properties of Mg-2Zn-0.5Zr-1.5Dy alloy was studied by optical microscopy (OM), immersion experiment and electrochemical experiment. The results show that the alloy has the best comprehensive properties when the solution temperature is 470°C. The minimum average grain size was 97 μm. The Icorr and Eb of as-cast alloy are-3.55 μA/cm2 and-1.27 V, respectively, according to polarization curve fitting. With the increase of solution temperature, the value of Icorr first decreases and then increases, and Eb first increases and then decreases. After solution treatment at 470°C, Icorr and Eb are 1.41 μA/cm2 and-1.14 V, respectively.

Effect of Solution Temperature on Microstructure and Mechanical Properties of Ti–5Al5Mo5V3Cr1Zr Alloy

The work aims to reveal relationship between solution temperature, microstructure, and mechanical properties of Ti–5Al5Mo5V3Cr1Zr (Ti‐55 531) alloy. The alloys are prepared via solution processing in a temperature ranging from T β − 100 °C (where T β is β‐transus temperature) to T β + 100 °C for 2 h; and then air cooled, aged at 600 °C for 6 h, and air cooled again. Results indicate that solution temperature range (from T β − 100 °C to T β + 100 °C) can be divided into following five ranges according to performance of Ti‐55 531 alloy. The alloy presents excellent mechanical performance combining high strength and good ductility for solution temperatures ranging from T β − 50 °C to T β − 30 °C and from T β + 10 °C to T β + 30 °C. Interestingly, the Ti‐55 531 alloy exhibits a dramatically enhanced strength, while ductility drops rapidly as solution temperature exceeds T β + 70 °C. The enhanced strength's main reason is that grain boundary α phase changes from continuous to discontinuous with increasing solution temperature; nevertheless, the increased size of β grains results in a reduction in ductility. Thus, continuity of grain boundary α phase has a dramatical influence on performance of Ti‐55 531 alloy.

Hemigraphis colorata (HC) Leaves Extract as Effectual Green Inhibitor for Mild Steel Corrosion in 1M HCl

The corrosion inhibitory effect of Hemigraphis colorata (HC) leaves extract on mild steel in 1M HCl was investigated using mass loss measurements, ultraviolet-visible(UV) spectroscopy, Fourier transform infrared spectroscopy(FT-IR), electrochemical impedance spectroscopy (EIS), and Tafel polarization techniques at the temperature range of 303K-323K. The optimum inhibition efficiency of HC extract at 303K, 313K, and 323K was found to be 90.2%,92.77%, and 93.73%, respectively, for the maximum concentration of the extract. This suggests that inhibition efficiency was found to increase with increasing concentration of the leaves extract at all the temperatures and increasing solution temperature. The adsorption process complied with a Langmuir adsorption isotherm. Polarization measurements suggest a mixed mode of corrosion inhibition. The activation energy and other thermodynamic parameters were calculated for the process of inhibition. The adsorbed invisible layer was investigated using scanning electron microscopy, which revealed better morphology of mild steel in extract presence. Using energy-dispersive X-ray spectroscopy, the effect of HC extract on the interfacial behavior of mild steel surface was analyzed.

Effects of heat treatment on γ′ precipitates and tensile properties of a Ni-base superalloy

Different heat treatments (solution temperatures: from 1100 °C to 1140 °C) were performed to optimize the microstructures improving the mechanical properties of a wrought superalloy GH4151. The solution treatments essentially affected the area fraction of γ′ precipitates and the grain size of γ matrix. The dissolution kinetics model of primary γ′ precipitates was calculated. The results showed that the fine primary γ′ precipitates inside of grains dissolved first when the solution temperature below 1120 °C, while the coarse primary γ′ precipitates dissolved obviously as solution temperature above 1130 °C. Moreover, the grain growth occurred when the solution temperature exceeded 1130 °C. Besides, a higher area fraction of secondary γ′ precipitates with nearly spherical morphology were precipitated from the matrix during the subsequent aging process. The size of secondary γ′ precipitates increased with the increase of solution temperature. Then tensile tests were carried out at room temperature (RT) and 750 °C, the results showed that the alloy suffered solution treated at 1130 °C possessed the optimum tensile properties at 750 °C on account of the high area fraction of medium-sized secondary γ′ precipitates. However, the strength of alloy solution treated at 1140 °C decreased mainly because of the larger secondary γ′ precipitates. Meanwhile, the fracture mechanism changed from the ductile fracture to a mixed ductile and brittle fracture with the solution temperature rising.

Effect of Solution Treatment on Microstructure and Mechanical Properties of TC16 Titanium Alloy Wire

Abstract TC16 titanium alloy wire was treated by solution treatment, and then the optical microscope, tensile property and impact property tests were used to analyze the microstructure and mechanical properties of TC16 titanium alloy wire after solution treatment. The results show that there are a lot of primary α phase, metastable β phase and α” phase after solution treatment. With the increase of solution temperature, the content of primary α phase decreases to completely disappear and more α” phase is formed. Under the condition of solid solution, the tensile strength decreases with the increase of temperature, while the plasticity changes little with the increase of temperature. The maximum tensile strength is 969 MPa, the maximum yield strength is 572 MPa, the maximum elongation after fracture is 26 %, and the maximum section shrinkage is 59 %. The impact toughness and impact absorption energy increase with the increase of solid solution temperature, and the maximum impact toughness is 90 J/cm2, and the maximum impact absorption energy is 37 J.

Effect of Solution Temperature on the Microstructure and Properties of 17-4PH High-Strength Steel Samples Formed by Selective Laser Melting

Samples of 17-4PH high-strength steel were processed by selective laser melting (SLM) and solution-processed. The effects of the solution temperature on the microstructure and mechanical properties of the samples were studied. The 17-4PH high-strength steel is primarily composed of martensite, with a small number of austenite phases, and contains many dislocations. After the solution treatment, the grain size gradually increased, yielding typical martensite. The samples were subjected to an aging treatment after the solution treatment. Precipitates formed in the samples, conducive to improving their strength and hardness. The Vickers hardening and wear properties of the 17-4PH high-strength steel samples first increased and then decreased with increasing solution temperature. After the solution treatment at 1040 °C for 2 h and aging at 480 °C for 4 h, the Vickers hardening of the 17-4PH high-strength steel increased to 392 HV0.5, and the friction coefficient was approximately 0.6. These values were, respectively, 7% and 5% higher than those for the untreated samples.

Characteristics of Fiber Bragg Grating Due to Temperature Changes in Honey Solution

The high sensitivity and low power consumption of Fiber Bragg grating (FBG), has been widely applied in optical technology to measure temperature and strain. Currently, the need for detection by the industrial sector is increasingly being developed, one of which is the detection of characteristics in honey solutions. The use of FBG as a detector has a great opportunity to see the unique characteristics of the honey solution. Therefore, this problem needs to be followed up by analyzing the effect of honey temperature on the FBG output power, changes in Bragg wavelength, and the rate of temperature change. The research method was carried out by placing FBG in a heated honey solution, then measuring the temperature between 30 - 60 °C with an increase of 5 °C. The FBG used consists of a wavelength of 1550 nm and 1310 nm which is fed with 1 milliwatt of input power. The results showed that the highest output power of FBG against honey solution B was in the range of 213.60 × 10-6 - 214.58 × 10-6 W. Changes in Bragg wavelength were quite significant for the increase in temperature of honey solution with a difference of 0.58 - 0.76 nm.

Thermodynamics, isotherms, and mechanisms studies of lithium recovery from seawater desalination reverse osmosis brine using roasted and ferrocyanide modified date pits

In this study, the adsorption isotherms and thermodynamic studies of lithium ions from seawater reverse osmosis (SWRO) desalination brine were investigated. Three adsorbents were utilized namely, roasted date pits (RDP), potassium copper, and nickel hexacyanoferrate-date pits (RDP-FC-Cu and RDP-FC-Ni). The prepared adsorbents showed enhanced morphological and chemical structures such as high porosity, carbonaceous composition, larger pore and volume sizes, smaller particle sizes as well as the presence of unique functional groups on their surface. The adsorption of lithium ions onto the three adsorbents was enhanced with an increase in solution temperature and initial lithium concentration. The temperature that showed the highest adsorption of lithium ions onto the three adsorbents was 45 °C. The adsorption of lithium ions onto the three adsorbents was the highest at an initial lithium concentration of 100 mg/L. The three adsorbents achieved an adsorption capacity of around 99 mg/g at the optimum temperature and initial concentration. On the other hand, RDP-FC-Cu achieved the highest adsorption capacities for lithium ions at all the studied initial concentrations. The thermodynamic study showed that the adsorption process of lithium ions onto the adsorbents is endothermic, spontaneous, and favorable at all the studied temperatures (25 °C, 35 °C, and 45 °C). Moreover, the adsorption of lithium ions onto the three adsorbents followed the Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin adsorption isotherm models differently at each studied temperature. For RDP, the adsorption process followed the Freundlich adsorption isotherm model at 25 °C, while it was more fitted to the Langmuir isotherm model at 45 °C and all models at 35 °C. The adsorption of lithium ions onto RDP-FC-Cu followed Langmuir adsorption isotherm model at 25 °C and 35 °C, while it fitted all models at 45 °C. On the other hand, Langmuir and Dubinin–Radushkevich isotherm models were best fit for the adsorption of lithium ions onto RDP-FC-Ni at 25 °C and 35 °C. The desorption study presented 99% desorption percentages of lithium ions from all the adsorbents, which showed the great regeneration potential of the adsorbents. Furthermore, the selectivity study showed that RDP-FC-Cu achieved 99.9% adsorption removal of lithium ions from the SWRO brine while RDP-FC-Ni and RDP achieved 99.8% and 99.3% adsorption removals, respectively. Finally, the cost analysis revealed that the total cost for the preparation of the adsorbent was 29.81 USD. • Three adsorbents were prepared to study the adsorption thermodynamics of lithium. • The prepared adsorbents showed high porosity, larger pore and volume sizes. • The adsorption capacity was increased by temperature and metal concentration. • Adsorption process of lithium onto the adsorbents was endothermic and spontaneous. • Desorption study presented 99% of lithium ions from all the adsorbents.

Plant extract mediated synthesis of Fe3O4-chitosan composite for the removal of lead ions from aqueous solution

Divalent lead ion contamination in drinking water pose adverse health effect, hence its removal using minute amount of chemical (Fe3O4) with the use of natural biopolymer (Chitosan) and green plant extracts Ricinus communis (Castor plant) for the synthesis of nanocomposites was determine in the present study. The phyto-magnetic nanomaterial was synthesized via co-precipitation method and characterized using Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform-Infrared spectrometer (FTIR) and X-ray diffractometer (XRD) techniques. The application of the green synthesized (RC-Fe3O4-Chitosan) nanocomposites was determined in the adsorption of Pb(II) from aqueous solution. The experimental parameters such as contact time, pH range, adsorbent dosage, and effect of temperature were evaluated. The results showed that the maximum adsorption capacity of the divalent lead ions occurred at pH = 7.0, temperature = 323 K, contact time = 60 min and adsorbent dose = 0.3 g/L. The adsorption equilibrium was best fitted to the Freundlich isotherm. The maximum capacity determined from Freundlich isotherm was 50.72 mg/g at 323 K. Adsorption kinetics of Pb(II) was best described with pseudo-second-order kinetic model. Thermodynamics studies reveal that with an increase of solution temperature (303 K, 313 K and 323 K) the adsorption efficiency increases correspondingly to −4.35, −6.12, and −7.91 kJ/mol respectively, suggesting endothermic nature of the adsorption process. The reusability of the green synthesized adsorbent (RC-Fe3O4-chitosan) depicts seven successful sequential cycles. Therefore, the synthesized green magnetite chitosan composites can be used as a reliable and sustainable material for efficient removal of Pb(II)species from aqueous solution.

Inhibition of adhesion of CaCO3 scale by polydopamine/polytetrafluoroethylene coating with stability and anticorrosion properties

AbstractReduction of calcium carbonate (CaCO3) scale formation on the equipment surface is essential in a wide variety of industrial fields. In this work, polydopamine/polytetrafluoroethylene (PDA/PTFE) coating prepared by the simple immersion on stainless steel (SS) surfaces was developed to suppress the CaCO3 scale adhesion. The PDA/PTFE‐coated surface showed the higher hydrophobicity (water contact angle = 133.50°) and lower surface free energy (11.92 mN/m) than the stainless‐steel surface. The scale inhibiting rate of the coated surface was up to 76.8% after 12‐hour immersion in the CaCO3 solution in comparison with the untreated SS. More bubbles were observed on the PDA/PTFE‐coated surfaces, and the number of bubbles increased with increasing solution temperature leading to less area for the scale adhesion. As a result, the PDA/PTFE coated surfaces have the higher antiscale ability at the higher solution temperature. Furthermore, the stripping and electrochemical corrosion tests demonstrated that the PDA/PTFE coating has the better stability and anticorrosion ability. The PDA/PTFE coating with the superior properties has potential application for the long‐lasting reduction of the scale formation.

Comparative empirical evaluation of the aqueous adsorptive sequestration potential of low-cost feldspar-biochar composites for ivermectin

Several recent studies are shedding light on the potential of synergistically combined low-cost adsorbents for organic and inorganic contaminants removal in water treatment. However, there exists a dearth of data for their potential for removal of emerging contaminants. In this study, low-cost feldspar (FLC) was combined with blended Carica papaya or pine cone seeds (ratio of 1:1), and calcined to obtain FLC-Carica papaya seeds (FPA) or FLC-pine cone seeds (FPC) composites which were characterized. The composites were evaluated for ivermectin sorption by varying experimental pH, time, concentration and temperature, as well as their potential for reusability. The FLC structural lattice was not significantly affected by the modification process but the composites exhibited physicochemical features which were markedly different, having new FTIR spectra bands, well reduced surface area, and enhanced cation exchange capacity. The composites ivermectin sorption rates and equilibrium were faster (60 min) than the FLC (360 min). Ivermectin sorption was pH and concentration dependent. The sorption data fitted better to the homogeneous fractal pseudo-second order (FPSO) kinetics and Freundlich adsorption isotherm model; implying that the process involves complex sorption mechanism. The process was exothermic and increase in solution temperature up to 39.5 ºC did not enhance sorption. Ivermectin sorption capacity and rate trends were similar: FPA (110.9 µg/g) >FLC (84.6 µg/g) >FPC (62.7 µg/g). The FPA exhibited the best sorption capacity as well as the best reusability with over 64% of its initial sorption capacity retained on first reuse. The FPA also exhibited high potential to reduce ivermectin in low concentration solution (≈75 µg/L) to zero, with the trend of FPA ≤FLC (5.0 ± 1.5 µg/L) >FPC (≈27.5 µg/L). Though this kind of composite possesses economic potential in water treatment applications, not every biochar modification may result in enhanced sorption process.

Influence of Temperature in Degradation of Organic Pollution Using Corona Discharge Plasma

Dye solution temperature influences the elimination efficiency of water-soluble and anionic acid dye. Acid Blue 25 dye, using a gas–liquid electrical discharge system, was successfully investigated. The results showed an increase in the percentage of dye decolorization from 91.16% to 96.12% when the dye solution temperature was increased from 278 K to 308 K. However, the initial dye decolorization percentage was decreased with the further increase in dye solution temperature from 318 K to 358 K. The 2D simulation model was introduced to consider the influence of temperature and the electric field generated by corona discharge plasma in air and water. Results also showed a great match between the experimental and the simulation results. The reaction rates of dye degradation were analyzed using the Arrhenius equation. Furthermore, pseudo-zero-, pseudo-first-, and pseudo-second-order models were used to determine the reaction kinetics. The best fit for the experimental data would follow the pseudo-first-order model. Finally, electrical energy per order, energy yield, and experimental degradation data were calculated to investigate the cost analysis.

Impact of Ionic Liquid on Hydrogen Production from Waste Oilfield Water.

We present a promising method for producing pure hydrogen energy from the dissolution of zinc metal in waste oilfield water (WOW) under various conditions. This process mainly consumes zinc metal and WOW. The results show robust dependence on the temperature and solution pH of the hydrogen gas output. Low pH (2.5) and high temperature (338 K) were discovered to be the better conditions for hydrogen production. The 1-ethyl-3-methylpyridinium ethyl sulfate (EMP-ES) ionic liquid is used to regulate the rate of hydrogen generation for the first time. It has been confirmed that the rate of the dissolution of zinc increased faster and produced more hydrogen per unit of time by an increase in solution temperature and a decrease in solution pH. The adsorption of EMP-ES on the active sites of the Zn surface is unrestrained with mixing physical and chemical orientations. SEM, EDX, and FTIR spectroscopy inspections have been utilized to identify and characterize surface corrosion of zinc in WOW. Furthermore, this process is completely secure and can generate energy on demand.

Evaluation of Corrosion Inhibition Efficiency of Aluminum Alloy 2024 by Diaminostilbene and Azobenzene Schiff Bases in 1 M Hydrochloric Acid

The Schiff base compounds N,N ′ -bis(salicylidine)-4,4 ′ –diaminostilbene(SDS) and N,N ′ -bis(salicylidine)-4,4 ′ -diamino azobenzene(SDA) were synthesized, and their molecular structure was determined by FT-IR and 1H NMR. The corrosion inhibitions of Schiff base compounds on aluminum alloy 2024 in 1 M hydrochloric acid were evaluated by potentiodynamic polarization, impedance techniques, weight loss method, and scanning electron microscopic technique. The potentiodynamic polarization (PDP) studies revealed that SDS and SDA compounds acted predominantly as cathodic inhibitors. The electrochemical impedance spectroscopic (EIS) parameters confirmed the adsorption of SDS and SDA molecules over the surface of aluminum alloy 2024 alloy by forming an inhibitive layer. The weight loss studies showed that the inhibition efficiency of these compounds increases directly with concentration and decreases with an increase in solution temperature and immersion time. The thermodynamic parameters were calculated to investigate the mechanism of corrosion inhibition. The SDA was found to be more effective than SDS and followed the Langmuir adsorption isotherm model. The scanning electron microscopy (SEM) results revealed that the deterioration of the alloy surface is minimal in the presence of an inhibitor. Both Schiff base molecules exhibited superior corrosion inhibition for aluminum alloy 2024 alloy in HCl medium.

The Formation of 14H-LPSO in Mg-9Gd-2Y-2Zn-0.5Zr Alloy during Heat Treatment.

There is a new long-period stacking ordered structure in Mg–RE–Zn magnesium alloys, namely the LPSO phase, which can effectively improve the yield strength, elongation, and corrosion resistance of Mg alloys. According to different types of Mg–RE–Zn alloy systems, two transformation modes are involved in the heat treatment transformation process. The first is the alloy without LPSO phase in the as-cast alloy, and the MgxRE phase changes to 14H-LPSO phase. The second is the alloy containing LPSO phase in the as-cast state, and the 14H-LPSO phase is obtained by the transformations of 6H, 18R, and 24R. The effects of different solution parameters on the second phase of Mg–9Gd–2Y–2Zn–0.5Zr alloy were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The precipitation mechanism of 14H-LPSO phase during solution treatment was further clarified. At a solution time of 13 h, the grain size increased rapidly initially and then decreased slightly with increasing solution temperature. The analysis of the volume fraction of the second phase and lattice constant showed that Gd and Y elements in the alloy precipitated from the matrix and formed 14H-LPSO phase after solution treatment at 490 °C for 13 h. At this time, the hardness of the alloy reached the maximum of 74.6 HV. After solution treatment at 500 °C for 13 h, the solid solution degree of the alloy increases, and the grain size and hardness of the alloy remain basically unchanged.

Effect of post-weld solution treatment on microstructure and mechanical properties of electron beam welded IN738LC joint

The effect of post-weld solution treatment (PWST) on microstructure and mechanical properties of electron beam welded IN738LC joint has been investigated. The fusion zone (FZ) of IN738LC joint consisted of γ-Ni matrix, fine γʹ particles, granular MC carbides and a bit of M23C6 carbides after PWST. With the increased solution temperature, the area percent of MC carbides decreased while the content of γʹ particles increased gradually. The solvus temperature of γʹ phase in FZ and base metal (BM) was 1150 °C and 1175 °C, respectively, which was due to the different size of primary γʹ particles. When the complete dissolution of primary γʹ particles in FZ and BM occurred, the micro-hardness of FZ and BM reached the peak values (509.5 HV and 503.9 HV). As the solution temperature increased, the tensile strength of IN738LC joint initially increased and then decreased, while the stress-rupture life of IN738LC joint decreased steadily. The joint with bimodal-size γ′ particles and moderate MC carbides after 1125 °C/2 h heat treatment showed the excellent comprehensive mechanical performance, and the average strength and stress-rupture life of IN738LC joints were 686 MPa (900 °C) and 2.395 h (900 °C/350 MPa), respectively. Consequently, 1125 °C/2 h has been proposed as an optimized PWST process for IN738LC joint.