Effect Of Heat Treatment Conditions Research Articles

Effect of heat treatment condition on magnetic, electrical transport and magnetoresistance properties of La0.67Sr0.33MnO3 manganite coatings

Effects of three different heat treatment conditions (air, vacuum and nitrogen) on the structure, magnetic, electrical transport and low-field magnetoresistance behaviors of La0.67Sr0.33MnO3 manganite coatings synthesized by sol-gel and screen printing methods have been systematically investigated. The detailed crystallographic analyses revealed that the diffraction peak positions of the samples subjected to annealing in vacuum and nitrogen ambients shifted to lower-angle regions, and lattice parameters and structure distortion increased as compared with those of the sample annealed in air, which were due to the introduction of oxygen deficiency under the annealing conditions of vacuum and nitrogen. The content of oxygen deficiency of the samples could be determined by the change of lattice parameters. Furthermore, the vacuum and nitrogen annealed samples exhibited a dramatic increase in the resistivity, accompanied by the reduction in ferromagnetism, the resistivity peak temperature and the ferromagnetism transition temperature. These phenomena were attributed to the decrease of average manganese oxidation state, as a result the mobile charge carriers were reduced, the ferromagnetic coupling and the double exchange effect between manganese ions decreased while the magnetic inhomogeneity increased. In the meanwhile, magnetoresistance ratios of the oxygen-deficient samples were enhanced around the percolation threshold.

Effect of heat treatment conditions on magnesium borate fibers prepared via electrospinning

The influence of different heating rates as well as different atmospheres on magnesium borate fibers produced by electrospinning was investigated in this work. The green fibers were prepared from sol–gel precursors, using polyvinyl-pyrrolidone (PVP) as processing aid. Crystalline fibers with the typical necklace structure and average diameter in the range 300–500 nm were produced when heating up to 900 °C in air. The main phase detected by XRD analysis was in this case Mg2B2O5. On the other hand, the fibers slowly heated in reducing atmosphere to 800 °C exhibited similar dimension but a different morphology. The crystalline grains were presumably smaller, hence the necklace effect was absent. This sample also revealed a much higher specific surface area in comparison to the samples calcined in air. Mg3B2O6 was here the main crystalline phase, while a part of boron was lost during the thermal treatment.

Effect of Heat Treatment Condition on the Characteristics of MnO<sub>2</sub> Added-Fe<sub>2</sub>TiO<sub>5 </sub>Ceramics for NTC Thermistors Using Local Iron Oxide

A study on the effect of heat treatment condition on the characteristics of MnO2 added-Fe2TiO5 ceramics for NTC thermistor has been carried out. The ceramics were produced by pressing an homogenous mixture of Fe2O3 (local/ yarosite), TiO2 and MnO2 (2.0 mole %) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1050 °C for 3 hours in oxygen gas. Some sintered pellets were heat treated by heating them at 300 °C for 5, 15 and 25 minutes in Ar + 7% H2 gas. The XRD analyses showed that the Fe2TiO5 ceramics with and without heat treatment time had orthorhombic structure. No peak from second phase was observed from the XRD profiles. From the electrical characteristics data, it was known that the heat treatment could change the electrical characteristics of the Fe2TiO5 based-thermistor. The thermistor constant (B) and room temperature resistivity (ρRT) decreased with the increasing of heat treatment time. All ceramics made had thermistor characteristics namely B = 3459-7596 K and ρRT = 1.056-6936.062 MΩcm. Thermistor constant of the ceramics was relatively big, indicated that ceramics made from local iron oxide in this work fit the market requirement for NTC thermistor.

複合ロールの残留応力に及ぼす熱処理条件およびロール直径の影響

複合ロールの残留応力に及ぼす熱処理条件およびロール直径の影響

Effect of Heat Treatment Condition After Hot Forging on Behavior of Aluminum Nitride Precipitation and Austenite Grain Growth on Successive Reheating Process in Case Hardening Steel

Effect of Heat Treatment Condition After Hot Forging on Behavior of Aluminum Nitride Precipitation and Austenite Grain Growth on Successive Reheating Process in Case Hardening Steel

Effect of Heat-treatment Conditions on Toughness in Laser Beam Welds of Reduced Activation Ferritic/martensitic Steel F82H

Effect of Heat-treatment Conditions on Toughness in Laser Beam Welds of Reduced Activation Ferritic/martensitic Steel F82H

Heat Treatment of Tantalum and Niobium Powders Prepared by Magnesium-Thermic Reduction

Changes in the specific surface area and porous structure of tantalum and niobium powders, which were prepared by magnesium-thermic reduction of Ta2O5, Mg4Ta2O9, and Mg4Nb2O9 oxide compounds and subjected to heat treatments at temperatures of 600–1500°C, have been studied. It is noted that, owing to the mesoporous structure of the magnesium-thermic powders, the decrease in the surface area during heat treatment, first of all, is related to a decrease in the amount of pores less than 10 nm in size. The heat treatment of a reacting mass is shown to allow us to correct the specific surface area of the powder without any increase in the oxygen content in it. Data on the effect of heat treatment conditions on the specific charge of capacitor anodes are reported.

Tribological Response of Heat Treated AISI 52100 Steels Against Steel and Ceramic Counterparts

Abstract AISI 52100 bearing steels are commonly used in applications requiring high hardness and abrasion resistance. The bearing steels are working under dynamic loads in service conditions and their toughness properties become important. In order to provide the desired mechanical properties, various heat treatments (austenizing, quenching and tempering) are usually applied. In this study, AISI 52100 bearing steel samples were austenized at 900°C for ½ h and water quenched to room temperature. Then tempering was carried out at 795°C, 400°C and 200°C for ½ h. In order to investigate the effect of heat treatment conditions on wear behavior, dry friction tests were performed according to ASTM G99-05 Standard with a ‘ball-on-disk’ type tribometer. The samples were tested against steel and ceramic counterparts using the parameters of 100 m distance and 30 N load and 0.063 m/s rotational speed. After wear test, the surface characterization was carried out using microscopy. Wear loss values were calculated using a novel optical method on both flat and counterpart specimens.

Fabrication and Characterization of Photocatalyst Coatings by Heat Treatment in Carbon Powder for TiC Coatings

Photocatalyst coatings on alumina (Al2O3) balls had been successfully fabricated by mechanical coating technique, with titanium carbide (TiC) powder and subsequent heat treatment in carbon powder. The effect of heat treatment conditions in carbon powder on the formed compounds, surface morphology and photocatalytic activity of photocatalyst coatings was investigated. XRD results show that the formed compounds change with increasing the heat treatment temperature in carbon powder, and rutile TiO2 on the surface of TiC coatings at 1073 K and 1173 K. The generated oxygen vacancies confirmed by XPS measurement, are in favor of narrowing band gap to enhance the visible-light photocatalytic activity of photocatalyst coatings. The photocatalytic activity of photocatalyst coatings has been effectively enhanced, and the samples fabricated at 1073 K and 1173 K for 2 h show higher activity. The fabrication strategy provides us a facile preparation procedure of visible-light responsive photocatalyst coatings.

Effect of heat treatment conditions on the growth of MgAl2O4 nanoparticles obtained by sol-gel method

Abstract MgAl 2 O 4 nanoparticles (NPs) were prepared by sol–gel method using aluminium nitrate, magnesium nitrate and citric acid as starting materials, phenolic formaldehyde resin and carbon black as additives. Growth of MgAl 2 O 4 NPs in different heat treatment conditions (temperature, atmosphere, carbon additives and in Al 2 O 3 -C system) was investigated. MgAl 2 O 4 NPs were formed at 600 °C in air atmosphere with serious agglomeration of nanoparticles having diameter of approximate 30 nm. The size of MgAl 2 O 4 NPs increased greatly from 40 to 50 nm to several hundreds of nanometres as the temperature was raised from 800 °C to 1400 °C. Partial sintering of NPs was observed upon heating at temperatures higher than 1200 °C in air. In reducing atmosphere, the size of MgAl 2 O 4 NPs (about 30–50 nm) changed slightly with increasing temperature. This was attributed to the dispersion of carbon inclusions in the MgAl 2 O 4 grain boundaries, inducing a steric hindrance effect and inhibiting the growth of particles. MgAl 2 O 4 NPs (30–50 nm) in the Al 2 O 3 -C system were in-situ formed at high temperatures with the use of dried precursor gels. MgAl 2 O 4 NPs can contribute to improving the thermal shock resistance of Al 2 O 3 -C materials.

Microstructure and mechanical property relationship for different heat treatment and hydrogen level in multi-pass welded P91 steel joint

The effect of heat treatment condition and diffusible hydrogen level on microstructure and mechanical properties of multi-pass shielded metal arc welded (SMAW) P91 steel butt joints of 18mm thickness has been studied. Field-emission scanning electron microscope (FESEM), Mercury diffusible hydrogen measurement, Charpy test, room-temperature tensile testing, hardness measurement and energy dispersive X-ray spectroscopy (EDS) were performed to characterize the multi-pass SMAW joints in as-welded, post-weld heat treatment (PWHT) and normalizing/tempering (N&T) state. The P91 steel butt joints with low level of diffusible hydrogen exhibited higher tensile strength and toughness. Both PWHT and N&T treatment provided similar mechanical properties but a significant microstructure variation was noticed for different zones of P91 welds. N&T treatment produced the homogenize microstructure along the P91 weldments both in terms of microstructure and micro-hardness.

Effect of heat treatment conditions on the passivation behavior of WE43C Mg–Y–Nd alloy in chloride containing alkaline environments

Mg–Y–Nd alloy (WE43C or Elektron 43) is a heat treatable magnesium wrought alloy that can be used up to 250 °C for aerospace application. This alloy has excellent mechanical properties (UTS: up to 345 MPa at room temperature) and improved corrosion resistance. Electrochemical passivation studies were conducted on this alloy under different heat treatment conditions in 0.1 M NaOH solution with the addition of chloride from 0 to 1000 ppm. The passive potential range typically extended to more than 1.5 VAg/AgCl. The transpassive potential was not dependent on the heat treatment condition of the alloy when the chloride concentration increased up to 500 ppm. However, pitting protection potential varied with the heat treatment condition when the chloride addition was 500 ppm or more. The specimen surface was analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy to understand the passivation behavior of this alloy. The passivated surface of the WE43C specimens indicated that the surface layer consisted of MgO, Mg(OH)2, and rare earth oxide phases, and the heat treatment conditions did not significantly affect the composition of the surface film.

Effect of heat-treatment conditions on the structure and phase transformations in the shape-memory 45Ti–45Ni–10Nb alloy in as-cast and extruded states

The effect of the types and conditions of heat treatment on the element composition, microstructure, phase composition, kinetics and temperatures of phase transformations, crystal lattice and substructure parameters, and mechanical characteristics of the shape-memory 45Ti–45Ni–10Nb (at %) alloy in the ascast and extruded states was studied. The interrelation between the structure features of the alloy and its mechanical characteristics was found. The conditions of heat treatment and the state of the alloy, which assure its high mechanical characteristics, were determined.

Effect of Heat Treatment Conditions on Micro Structure of Cast Iron

Article deals with problematice of influencing mechanical properties - tensile strength and hardness - of grey cast iron by heat treatment - refinement. Refinement could be in special cases applied also for grey cast iron castings in order to achieve special parameters of hardness and tensile strength of parts for specific purposes. Hardening and tempering of casting sis commonly used for ductile cast iron, but in special cases could be applied also for grey cast iron castings. Refinement - hardening and tempering - was provided on samples from materiål EN GJL 150, EN GJL 200 and EN GJL 250. Afterwards, measured values of tensile strength, hardness and fractography of materiål in poured state and after tempering on temperatures 250, 350 and 450°C after quenching from austenitization temperature 920°C were compared. Achieved results are formulated in the evaluation part of article.

Effect of heat treatment conditions on structure and properties of high-speed steel

High-speed steels made by powder and traditional metallurgical technology have been investigated. These steels are used for manufacturing of metalworking tools. Powder high-speed steels have a large safety margin and a high level of mechanical properties. Mechanical properties and the structure of steels S390 MICROCLEAN® and Fe-9%W-4%Mo-8%Co were compared after their hardening heat treatment. The composition of the carbides was determined by x-ray phase analysis. Residual stresses of the finished cutters were determined. It was shown that the mechanical properties of steels have been determined by the phase composition and the degree of carbides dispersion. The dependence of the microstructure and the high-speed steels phase composition on heat treatment conditions was identified. The conclusion about structure control effectiveness in the adjustment of heat treatment conditions of high speed steels was made.

Effects of Heat Treatment Conditions on Formation of Expanded-Austenite Phase in Austenitic Stainless Steels by Combining Active Screen and DC Plasma Carburizing Processes

Effects of Heat Treatment Conditions on Formation of Expanded-Austenite Phase in Austenitic Stainless Steels by Combining Active Screen and DC Plasma Carburizing Processes

Effects of Heat Treatment Conditions on Formation of Expanded-Austenite Phase in Austenitic Stainless Steels by Combining Active Screen and DC Plasma Carburizing Processes

Effects of Heat Treatment Conditions on Formation of Expanded-Austenite Phase in Austenitic Stainless Steels by Combining Active Screen and DC Plasma Carburizing Processes

Changes in Rice Husk by Heat Treatment

The effects of heat treatment conditions on the properties of rice husk were evaluated in this study. The commercial products of the heat treated rice husk were also investigated in terms of the changes in the properties by the manufacturing methods such as the indirect rotary kiln method and the direct combustion method. The indirect rotary kiln treatment for the commercial product resulted in the lower carbonization and the lower absorption of methylene blue of the heat treated rice husk product than those of the direct heat treated rice husk product. In addition, the effect heat treatment was analyzed under two different conditions - by using muffle furnace at air atmosphere condition and by using tube furnace at nitrogen atmosphere condition - for comparative analysis. The rice husk treated in nitrogen condition showed less carbonation, less changes in pH and no significant changes in methylene blue absorption properties, compared to the rice husk treated in the air condition. The pH of the rice husk treated in the air condition changed from 3.5 at 300°C treatment to 9.5 at 500°C treatment. Also, the absorption capacity of the rice husk treated in the air condition was greatly improved as the treatment temperature increased.

Effect of heat treatment conditions on MnFe(P,Si,B) compounds for room-temperature magnetic refrigeration

Mn1.000Fe0.950P0.595Si0.330B0.075 compounds have been synthesized by high-energy ball milling and a subsequent solid-state reaction. The influence of the sintering conditions on the magnetic phase transition of Mn1.00Fe0.95P0.595Si0.33B0.075 samples has been systematically investigated using X-ray diffraction and magnetic measurements. The experimental results show that all the samples obtained after different heat treatment conditions crystallize in the Fe2P-type hexagonal structure. The annealing temperature has a strong influence on the Curie temperature, which can be tuned between 265 and 298 K by sintering the samples at different temperatures between 1273 and 1373 K. The annealing time, however, does not significantly affect the Curie temperature. Both the annealing temperature and the annealing time have a significant effect on the magnetic entropy change. The magnetic entropy change under a magnetic field change of 1 T increases from 2.7 to 6.5 J kg−1K−1 by increasing the annealing temperature from 1273 to 1373 K. By increasing the annealing time, the magnetic entropy change at first increases and then saturates after 20 h of heat treatment at 1373 K.

Quality control of heat treatment of oil and gas pipes using magnetic structuroscopy

The problem of the development of in-line nondestructive testing of mechanical properties of heat-strengthened oil and gas steel pipes remains topical. In this work, the effect of heat treatment conditions represented by the quenching temperature (in the range of 765–980°C) and cooling rate from the quenching temperature (in the range of 500–720°C, after quenching in water) on the structure, hardness, and magnetic properties (coercive force, residual induction, maximum magnetic permittivity, and saturation magnetization) is studied for the widely used pipe steels of 22KhG2A, 30KhMA, and 32G2 brands. The magnetic parameters are measured both in a closed magnetic circuit and using the attached magnetic devices on model and full-scale samples. A possible application of the coercimetric method as an alternative for the durametric one is shown for continuous underheating testing for quenching and the tempering quality of the pipes made from the steels under study during fabrication.