Influence Of Heat Treatment Temperature Research Articles

Synthesis of mace silver nanorod with particles and water-alcohol room-temperature-curing UV conductive ink

At present, the silver nanorods of UV conductive ink have the problems of easy agglomeration of silver nanorods, and slow curing speed. In this paper, firstly mace-like silver nanorods with inorganic particles were synthesized by using polycarbonate fibers as soft-templates, AgNO3 as silver source. The diameters and lengths of silver nanorods were 0.25–0.35 μm and 2.1–5.1 μm. There are many wolf-tooth particles (0.20–0.35 μm) on the silver nanorods which prevented the silver nanorods from reuniting. The obtained silver nanorods were not easy to agglomerate. The minimum resistance value of the coating could reach 1∼10Ω. Secondly, a kind of water-alcohol UV conductive ink with low heat treatment temperature (140 °C), fast drying and curing speed and water-alcohol system was prepared. Water-alcohol soluble P(AA-r-HEMA)-g-GMA was used as the prepolymer, glycidyl triethylenetetraamine hexamethacrylate (TGMA) was used as the monomer, and 907 and ITX were used as photoinitiators. The effects of the types and contents of different photoinitiators (907:1%–5%, ITX: 0.2 %∼1 %), species and contents of prepolymer (30 %∼50 %), the number and content of monomers with different functional groups (30 %∼50 %) on the UV-curing rate were studied. The curing rate was the fastest when the mass fraction of photoinitiator ITX was 0.4 %, the mass fraction of the prepolymer with 30 % GMA content was 50 % and the mass fraction of monomer TGMA was 50 %. The curing speed can reach 2–3 s, and the ink film surface was smooth without bubbles. At last, UV conductive ink was prepared by using the obtained water-alcohol UV curing system as the bonding material and mace-like silver nanorods as the conductive filler. The influence of heat treatment temperature and time on the conductive properties of the coating was explored. The optimal heat treatment temperature was 140 °C, and the heat treatment time was 30 min.

The Influence of Heat Treatment Temperature on Tensile Properties of Metal-Bonded Diamond Composites Fabricated via Selective Laser Melting.

Selective Laser Melting (SLM) is an effective technology for fabricating new types of porous metal-bonded diamond tools with complex geometries. However, due to the high cooling rate and internal stresses during SLM fabrication, defects such as high porosities and interface gaps still need to be resolved before it can be considered for use in other applications. The influence of heat treatment temperature on internal characterization, interface microstructures, and tensile properties of AlSi7Mg-bonded diamond composites fabricated by SLM were investigated in this work. From experimental results, the porosities of HT-200, HT-350, and HT-500 specimens were 12.19%, 11.37%, and 11.14%, respectively, showing a slightly lower percentage than that of the No-HT specimen (13.34%). Here, HT represents "Heat Treatment". For No-HT specimens, an obvious un-bonding area can be seen in the interface between AlSi7Mg and diamond, whereas a relative closer interface can be observed for HT-500 specimens. After heat treatment, the elastic modulus of specimens showed a relative stable value (16.77 ± 2.79~18.23 ± 1.72 GPa), while the value of yield strength decreased from 97.24 ± 4.48 to 44.94 ± 7.06 MPa and the value of elongation increased from 1.98 ± 0.05 to 6.62 ± 0.51%. This difference can be attributed mainly to the disappearance of the solid-solution hardening effect due to the increase of Si content after heat treatment.

Impact of fast heating and cooling on the mechanical behaviour of alumina-magnesia refractory castables

The alumina-magnesia castables is one kind of monolithic refractories for steel ladle, whose thermo-mechanical properties vary with temperature during the lining pre-heating process and metallurgical service. The understanding of their variation tendency and sensibility to temperature fluctuation is important for the improvement of high-efficiency pre-heating strategy and real-time service performance. In this study, the influence of heat treatment temperature and heating/cooling rate on the thermo-mechanical properties and fracture behaviour of alumina-magnesia castables is investigated using uniaxial compressive tests equipped with an induction heating system and Brazilian test combined with digital image correlation and acoustic emission. The brittleness and mechanical strength of alumina-magnesia castables increase with heat treatment temperature due to the better sintering and formation of calcium hexaluminate and spinel phases. Without full relaxation of residual stresses, the stiffness increases while the strength decreases after fast heating of 200 °C/min. Meanwhile. the same castables after different thermal treatments show disparate mechanical responses to cooling rates.

Influence of heat-treatment temperature on structural and electrical properties for BaSrTiO3 compounds

The sol-gel process was utilized in the production of the ferroelectric material Ba0.7Sr0.3TiO3. Barium and strontium acetate were employed as sources for Ba and Sr, respectively, and Ti(IV) isopropoxide was used as a source for Ti. The acetic acid was utilized as a solvent for Ba and Sr acetate, whereas 2-methoxy ethanol was used as a stabilizer for Ti (IV) isopropoxide. The effect of high temperatures on electrical and structural were studied. The FESEM revealed the particle size of all samples with different temperatures. The XRD shows the Ba0.7Sr0.3TiO3 samples have a tetragonal phase for all temperatures (1000, 1100, 1200˚C). The high temperatures impacted tetragonality and the lattice constant (a, c); the lattice constant decreased at higher temperatures. The ferroelectric sample sintered at 1000 degrees Celsius had dielectric characteristics that were inferior to those of the Ba0.7Sr0.3TiO3sample sintered at 1100 and 1200ºC degrees Celsius. When the dielectric constant was graphed as a function of temperature, the Curie temperature appeared to be between (28-32) degrees Celsius.

Binary mixed metal oxide sphere-like structures for hybrid supercapacitor electrode with improved electrochemical properties

The facile fabrication of stable and highly efficient metal oxide-based electrode materials by regulating the electroactive sites is crucial for supercapacitor applications. In this work, a two-step synthesis strategy comprising hydrothermal and heat treatment was employed to prepare the NiWO4/WO3 (NW/W-O) as electrode materials for supercapacitors. Moreover, the heat treatment temperature influences and alters the physicochemical and electrochemical properties of the obtained NW/W-O products. The material prepared at 500 °C (NW/W-O(A)) unveils low crystallinity, small particle size, and a large surface area with a narrow porous feature than the material obtained at 600 °C (NW/W-O(B)). Thus, the NW/W-O(A) electrode could be anticipated for effective charge transfer and better capacitive behavior. Notably, the NW/W-O(A) material exhibited a superior specific capacitance of 825 F g−1 than NW/W-O(B) with 536 F g−1 at a current density of 1 A g−1. Further, the NW/W-O(A) displayed a higher rate capability of 60% (@ 20 A g−1) than that of NW/W-O(B) (49%). The designed hybrid supercapacitor (NW/W-O(A)//AC) showed a high specific capacitance of 108 F g−1 and energy density of 33.77 Wh kg−1 at a power density of 896.39 W kg−1 with long-term cyclic retention of only <12% deterioration over 10,000 cycles. Hence, this work demonstrates that the influence of heat treatment temperature is a crucial parameter in tailoring electrode materials with promising energy storage capability.

Evaluation of the Effects of Substrate Heat Treatment and Monomer/Acid Ratio Synthesis Parameters on the Performance of PANI/CFF Electrodes

The association of capacitive charging of the double-layer and a faradic redox reaction is desirable on carbon fiber felt (CFF) when oxygen functional groups or other materials such as conducting polymers are present on its surface enhancing its capacitive properties. In this work, a systematic study of the composites formed by carbon fiber felt felt produced at two different heat treatment temperatures (HTT) of 1000 and 2000 ºC and polyaniline (PANI) was performed upon two approaches: influence of heat treatment temperatures of substrate CFF and monomer/acid ratio. CFF samples were produced from polyacrylonitrile (PAN) precursor at HTT of 1000 and 2000 ºC, with step temperature of 330 ºC h-1 under nitrogen atmosphere. The maximum level temperature was kept for 30 min and then, cooled down to room temperature. The CFF samples were cut in 1 cm2 with thickness about 2 mm. Afterwards, the PANI was electrodeposited on CFF under galvanostatic mode with current density of 5 mA cm-2, using 1:1 and 2:1 H2SO4/aniline mol L-1 aqueous solution at deposition time of the 1350 seconds, for both proportions acid/monomer. The obtained PANI/CFF binary composite was washed in acid solution and vacuum dried. The morphological and structural analyses were investigated by Field emission gun-scanning (FEG-SEM), Surface Area Analysis (BET – Brunauer, Emmett and Teller), Thermogravimetric analysis (TG) and Fourier-Transform Infrared Spectroscopy (FT-IR). Electrochemical responses were analyzed by galvanostatic charge/discharge, electrochemical impedance spectroscopy, and cyclic voltammetry.The electrochemical analyses are recorded in a three electrodes system using Ag/AgCl electrode as reference electrode and a platinum sheet as counter-electrode in deaired solution with N2 using a potentiostat PGSTAT 302 with FRA module (Metrohm – AUTOLAB). The charge/discharge (CD) tests are obtained by applying constant current I of ±1.0, 0.75 and 0.5 mA (Ecut-off from -0.1 to 0.78 V vs. Ag/AgCl). Cyclic voltammograms (CV) are recorded in previously defined potential at sweep rate range from 10, 25, 50, 75 and 100 mV s−1. The electrochemical impedance spectroscopy (EIS) measurements are performed at open circuit potential (OCP) with ± 10 mV of the potential amplitude in the frequency range from10-3 to 105 Hz in 1.0 mol L-1 H2SO4.As can be seen, the FFC 2000 2:1 sample with 1350 seconds of synthesis presents higher specific capacitance as well as higher coulombic efficiency compared to FFC 2000 1:1 sample also with 1350 seconds of synthesis, with values at around 80 F/g and 90% respectively. On the other hand, the CFF 1000 1:1 sample with 1350 seconds of synthesis present higher values (33 F/g and 100%) than the sample CFF 1000 2:1 with 1350 seconds of synthesis (26 F/g and 100%). In addition, the increase in the intensity of the Faradaic peaks that were provided by the greater presence of the monomer synthesized on the surface of the substrate. The analogous way the excess of monomer may favor the formation of polymer on polymer which will intensify, also the redox peaks and will also favor the formation of reticles providing that form para- (cross) bonds in addition to ortho- (linear) bonds. Therefore, it is suggested that in comparison to the FFC 2000 samples we have a greater favor of para- in the polymeric chains, for the FFC 1000 samples it is suggested that it has formed a greater number of ortho-type bonds, as can be seen in the FT-IR data. By FEG-SEM it is possible to verify that in CFF 2000 2:1 1350 seconds there is a smaller formation of the polymer film with agglomerates by the entire structure of the felt comparing with the microscopy of the sample CFF 2000 1:1 1350 seconds. Also, a smaller surface area and/or a smaller amount of pores available as noted in the N2 adsorption isotherm but it is similarly observed that polymer chains in overlapping layers, which also suggests the formation of para- providing lower values of specific capacitance and coulombic efficiency. Note that the N2 adsorption isotherm suggests that the CFF 2000 1:1 sample has greater surface area and/or greater amount of pores available on its surface compared to fiber under the same conditions, which contribute to the greater accumulation of charge and coloumbic efficiency on storage devices.

Influence of heat-treatment temperature on the improvement of the electrochemical performance of CoMoO4 nanomaterials for hybrid supercapacitor application

The rational design and construction of nanostructured materials have a great impact on the development of high-performance advanced electrode materials, which has attracted extensive attention to improve reliable and efficient energy storage devices. Herein, we report vertically aligned CoMoO4 nanoflakes with interconnected network-like porous structures as Faradic battery-type electrode materials for the advancement of supercapacitors (SCs). The nanoarchitecture CoMoO4 electrode materials were effectively fabricated through simple hydrothermal method and subsequent heat-treatment under different temperatures. Further, the effect of heat-treatment on the electrodes materials’ structural, morphological, and electrochemical properties were investigated by utilizing various characterization techniques. The unique nanoarchitecture of the 400 °C heat-treated CoMoO4 (CMO1) endows a facile pathway for the fast diffusion of the electrolyte ions and mass transfer reaction. Interestingly, the CMO1 (400 °C) electrode exhibits the specific capacity of 499 C g−1, which is higher than those of the CMO2 (500 °C) of 385 C g−1 and CMO3 (600 °C) of 260 C g−1, respectively. Furthermore, the hybrid supercapacitor (HSC) tailored with CMO1 as a positrode and activated carbon as a negatrode delivers a high specific capacitance of 102 F g−1 with excellent energy and power densities of 31.61 W h kg−1 and 19.29 kW kg−1, respectively.

Effects of heat treatment temperature and CeO2 content on the phase composition, structure, and properties of monazite phosphate-based glass-ceramics

The influences of heat treatment temperature and CeO2 content on the phase composition, structure, and properties of the monazite phosphate-based glass-ceramics prepared by a glass melt-quenching process were investigated. The results show that the CeO2 addition promotes the formation of monazite CePO4 phase but restrains the Fe(PO3)3 and Fe4(PO4)2O phases formed. The batches with high CeO2 content should be heat treated at higher temperatures to obtain the glass-ceramics with a single monazite CePO4 phase. Moreover, the mechanisms of the variations are discussed. At the heat treatment temperatures of ≤1200°C, the as-prepared glass-ceramics show good aqueous durability and the main networks of pyrophosphate and orthophosphate groups. The CeO2 loading can be increased up to 16 mol% from ∼9 mol% by forming the glass-ceramics through the melt-quenching process. The conclusions provide researchers with the roles of temperature and CeO2 in preparing monazite phosphate-based glass-ceramics as potential hosts for specific nuclear waste.

Crystallization behavior and density functional theory study of solution combustion synthesized silicon doped calcium phosphates

The influence of heat-treatment temperatures (700 °C, 900°C, 1200 °C) on the phase, physical properties, crystallization rate, and in vitro properties of the solution combustion synthesized silicon-doped calcium phosphates (CaPs) were investigated. The thermodynamic aspects (enthalpy, entropy, and free energy) of the synthesis process and the crystallographic properties of the final samples were first predicted and then confirmed using density functional theory (DFT). Results demonstrated that the crystallization rate was controlled by the fuel(s) type (glycine, citric acid, and urea) and the amounts of Si4+ ions (0, 0.1, 0.4 mol). The highest calculated crystallization rate values of the un-doped, 0.1, and 0.4 mol Si-doped samples were 64%, 22%, 38%, respectively. The obtained results from the DFT simulation revealed that crystal growth in the direction of c-axis of hydroxyapatite (HAp) structure could change the stability of (001) surface of (HAp). Also, the computational data confirmed the adsorption of Si–OH groups on the (001) surface of HAp during the SCS process with an adsorption energy of 1.53 eV. AFM results in line with DFT simulation showed that the observed change in the surface roughness of Si-doped CaPs from 2 to 8 nm could be related to the doping of Si4+ ions onto the surface of CaPs. Besides, the theoretical and experimental investigation showed that crystal growth and doping of Si4+ ions could decrease the activation energy of oxygen reduction reaction (ORR). Furthermore, the results showed that the crystallized HAp structure could have great potential to efficiently reduce oxidative stress in human body.

Influence of heat treatment temperature on the properties of the lithium disilicate‐fluorcanasite glass‐ceramics

AbstractThis study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate‐fluorcanasite glass‐ceramics and to develop new dental materials. The glasses and glass‐ceramics were prepared using CaF2‐SiO2‐CaO‐K2O‐Na2O‐Li2O‐Al2O3‐P2O5‐based glass system using a conventional melt quenching method followed by a two‐stage crystallization process. This two‐stage method involves two heating temperature steps: first at a constant temperature (TS1) of 600°C and second step at varying temperatures (TS2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass‐ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm3, 6.73 GPa, 3.38 MPa.m1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate‐fluorcanasite glass‐ceramics.

Graphite-like poly benzene networks (g-C6H3): Wurtz synthesis, structural characterization and electrochemical performance

Graphite-like poly benzene networks with benzene rings as building units (BUs) are prepared by the Wurtz reaction of 1,3,5-Trichlorobenzene with sodium at 380 °C in stainless steel autoclaves for the first time. The structural characteristics and electrochemical performances as anode materials in Lithium ion batteries of the as-prepared samples are then studied. Among them, structural characteristics test results unveil that the as-prepared samples possess graphite-like feature even though with poor crystallinity. In lithium ion storage performance tests, the sample PB-380 shows relatively higher reversible capacities of 573.7 mA h g−1 than that of sample PB-280, PB-480 and even graphite owing to the unique porous structure with benzene rings as building units. In addition, the influence of heat treatment temperature on structural characteristics, morphology and electrochemical performances of the key sample PB-380 are also studied. And it turns out that the structural rearrangement occurs in accompany with the removal of C, H atoms as heat treatment temperature increases.

Effect of Heat Treatment Temperature on Properties of Phosphogypsum Based Wall Materials

The waste of land resources and the destruction of ecological environment caused by the massive storage of phosphogypsum are becoming increasingly prominent. In order to solve this problem, industrial solid waste phosphogypsum was used to the main raw material in this paper and aimed at the building materials utilization of phosphogypsum, and prepared a phosphogypsum‐based wall material. Through the pretreatment of phosphogypsum at different temperatures, the influence of heat treatment temperature on the performance of phosphogypsum based wall materials was explored. The experimental results show that with the increase of heat treatment temperature, the setting time, volume density and mechanical properties of phosphogypsum‐based wall materials gradually increase, and the hygroscopicity first increases and then decreases. Based on the performance and energy consumption, the best performance after 160°C heat treatment, when the content of hemihydrate gypsum in phosphogypsum is 53.62%, sample bulk density is 1.304 g/cm^3, moisture absorption is 30.7%, compressive strength is 3.74 MPa.

Effect of Temperature on δ-Ferrite Morphology of Carbon Steel and Austenitic Stainless Steel Welds

δ-ferrite was formed in the weld metal when the melted metal solidified to the room temperature. The δ-ferrite morphology depended on the composition, temperature gradient and growth rate. Research on the influence of heat treatment temperature (400°C, 600°C, 900°C) on the morphology changes and the δ-ferrite content is presented in this paper using optical microscopy, SEM, TEM. The δ-ferrite concentration reduced continuously in increasing temperature (from 23.5% after welding to 11% at 900°C for 10 hours). Besides, the formation of sigma phase and carbides at 600°C were the main cause of increasing hardness values in the fusion zone. However, the heat treatment at a temperature of 900°C eliminated both the sigma phase and brittleness.

Intermediate-Temperature Heat Treatment of UNS N10003 Alloy during Cold Working

To explore an appropriate intermediate temperature of heat treatment during the cold working of UNS N10003 alloy, the influence of heat treatment temperature, time, the induced deformation, the mechanical properties, and microstructures by the pre-stretching method was investigated systematically. The results showed that after heat treatment (performed at 760 °C, 6 h), the strength was not reduced, and the elongation was not improved efficiently. However, after only 30 min of heat treatment at 870 °C, their strength was efficiently reduced, and their elongation was substantially improved, reaching the original sample level. Moreover, no apparent changes were observed with the extension of heat treatment time. The morphology of the microstructures and fractures indicated that the recovery and recrystallization process occurred at the temperature of 870 °C during the heat treatment, which resulted in the residual stress relieving and microstructural reconstruction. Correspondingly, the fractographs were also transformed from cleavage to ductile. Therefore, the heat treatment during the cold working should be carried out at 870 °C, enhancing energy- and cost-efficient production of UNS N10003 alloy.

Effect of Austenitizing Temperature on The Structural Evolution of Hot Forged Steel Grinding Balls

This paper reports the influence of heat treatment temperature on the microstructural changes that may occur in an XC38 forged steel grinding ball. Three austenitizing temperatures (870°C, 950°C and 1150°C) were used and a tempering at 250 °C followed by air cooling was carried out. Optical and scanning electron microscopies, as well as X-ray diffraction, were performed to investigate the microstructure and phase of the different samples. Microstructural analysis using the Rietveld method was conducted to access, for each temperature, the type and proportion of phases as well as crystallites size and microstrain. The obtained results were compared to those recorded on as forged steel. The effect brought by the variation of the austenitization temperature was well highlighted by the obtained results. The nature and proportion of microstructural phases were significantly affected by the increase of the austenitization temperature which was in favour of the increase of martensite content in a mixed microstructure consisting of bainite and martensite. A rising amount of martensite is noticed, with the increase of temperature, at the expense of the bainite content. An effect was also noticed on phase’s proportions, microstructural parameters, crystallites size and mircostrain.

Research on the influence of heat treatment temperature on bearing capacity of high steel grade pipeline during in-service welding

During the welding of in-service pipeline, natural gas is continuously transported in the pipeline, which maintains a high gas pressure. Therefore, the welding process is completed under strong cooling conditions, and welding delay crack is easy to occur. Preheating before welding and heat treatment after welding can effectively control the hardened microstructure, reduce the residual stress and ensure the welding quality. In this study, the influence of heating temperature on the bearing capacity of high steel grade pipe during in-service welding repair was studied. The high temperature tensile test was used to simulate the bearing capacity of the pipe under heating and high temperature environment. It is found that when the heating temperature is below 400°C, the pipe strength remains at the original level. With the increase of heating temperature, when the test temperature is higher than 400°C, the yield strength and tensile strength of the pipe decrease significantly. When the test temperature is 450°C, the yield strength and tensile strength of the material decrease by 15.8% and 11.1%, respectively, compared with the normal temperature, which are lower than the pipe standard requirements. Therefore, it is suggested that when the heat treatment temperature is higher than 400°C during in-service welding repair, it is necessary to consider reducing the pipeline pressure. At the same time, the box furnace heat treatment method was adopted to heat treat the pipe, and the tensile properties of the pipe after heat treatment were tested to analyze the bearing capacity of the pipe after heat treatment. It is found that when the heating temperature is higher than 700°C, the tensile properties of high grade pipeline steel pipe decrease sharply. It is suggested that when the heat treatment temperature is higher than 700°C, the risk assessment of the service safety of the heat treated pipeline should be carried out.

Intensification of preferred orientation in the additive manufactured Ti-6Al-4V alloy after heat treatment

The ductility of laser powder bed fusion (LPBF) Ti-6Al-4V alloy is generally low because the microstructure is α′-martensite. Heat treatment is widely used to improve the microstructure and ductility, though the preferred orientation after heat treatment is undetermined to date. This study identified the influences of heat treatment temperature on the preferred orientation of LPBF Ti-6Al-4V. The results showed a weak {112¯0}α′ texture along the building direction in the as-built Ti-6Al-4V. After 750 °C heat treatment, α′-martensite was transformed to α + β phases. The {112¯0}α preferred orientation gradually intensified as the heat treatment temperature was increased, as shown by X-ray diffraction and electron backscatter diffraction. After 950 °C heat treatment, {112¯0}α was mostly aligned with the building direction.

Nanomechanical Characterization of Iron Borides in Fe-Mn-B Ternary Alloys

Nanomechanical properties of iron borides, FeB and Fe2B were studied in Fe-Mn-B ternary alloys. The alloys were produced by arc melting method using high purity powders, which were subsequently annealed at temperature of 873 K and 1223 K, until fully equilibrated for a time period of 2160 hours and 1440 hours, respectively. Based on results obtained from experimental study and thermodynamic modeling of Fe-Mn-B system the solubility of Mn in these borides was determined. For the purpose of this study the influence of heat treatment temperature, as well as, the solubility of Mn in these borides on their nanomechanical properties is investigated. Nanomechanical properties, including determination of indentation modulus and hardness were measured using nanoindentation testing machine equipped with Berkovich type diamond indenter. The indentation process was carried out using an indentation depth controlled method, to a maximum depth of 500 nm.

Effect of heat treatment and thermomechanical processing on microstructure and tensile property of Ti-44Al-8Nb-0.2W-0.2B-0.5Y alloy

High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y, at.%) ingot was fabricated by vacuum arc remelting (VAR). The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed. The influence of heat treatment temperature and thermomechanical processing on the microstructure and tensile property of the alloy was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and tensile tests. It was found that the high Nb-TiAl alloy after HIP and annealing was mainly composed of coarse α2/γ lamellae, β/B2 phase and γ phase and the solidification path of this alloy was: L→L+β→β→α+β→α→α+β+γ→α2+β+γ. The water quenching results showed that the alloy was in α single phase region at 1,340 °C. After heating at 1,340 °C for 30 min followed by furnace cooling, the alloy showed a full lamellar microstructure and its ultimate tensile strength was about 538 MPa, with an elongation of 0.3% at room temperature. Free-crack forged pancakes with fine-grained fully lamellar structure (FFLS) were obtained with an initial deformation temperature of 1,340 °C and the ultimate tensile strength of forged alloy was about 820 MPa, with an elongation of 0.9% at room temperature, which was much higher than that of alloy after HIP and annealing because of microstructural refinement.

The Influence of Heat Treatment Temperature on Microstructures and Mechanical Properties of Titanium Alloy Fabricated by Laser Melting Deposition.

Ti-6Al-4V (TC4) titanium alloy parts were successfully fabricated by laser melting deposition (LMD) technology in this study. Proper normalizing temperatures were presented in detailed for bulk LMD specimens. Optical microscope, scanning electron microscopy, X-ray diffraction, and electronic universal testing machine were used to characterize the microstructures, phase compositions, the tensile properties and hardness of the TC4 alloy parts treated using different normalizing temperature. The experimental results showed that the as-fabricated LMD specimens’ microstructures mainly consisted of α-Ti phase with a small amount of β-Ti phase. After normalizing treatment, in the area of α-Ti phase, the recrystallized length and width of α-Ti phase both increased. When normalizing in the (α + β) phase field, the elongated primary α-Ti phase in the as-deposited state was truncated due to the precipitation of β-Ti phase and became a short rod-like primary α-Ti phase. In as-fabricated microstructure, the β-Ti phase was precipitated between different short rod-shaped α-Ti phases distributed as basketweave. After normalizing treatment at 990 for two hours with subsequent air cooling, the TC4 titanium alloy had significant different microstructures from original sample produced by LMD. The normalizing treatment methods and temperature can be qualified as a prospective heat treatment of titanium alloy fabricating by laser melting deposition.