Effect Of Heat Treatment Conditions Research Articles

The effect of heat treatment conditions using the drawing process on the properties of PET filament sewing thread

For the production of drawn poly(ethylene terephthalate) (PET) filament threads it is useful to determine the relationship between the drawing process conditions and the resulting product properties. Drawing at an elevated temperature over a defined time usually causes changes of the polymer structural parameters that influence the mechanical properties of the filaments. In order to elucidate the physical background of the drawing process for developing the production process of PET filament sewing thread, the thread was drawn by varying the treatment temperature and contact time. The effect of the treatment conditions on the structural and mechanical properties of the drawn threads was investigated, such as the birefringence, crystallinity, and dynamic mechanical properties of the threads’ filaments, as well as the mechanical properties and shrinkage of the treated threads. Using the drawing process, higher temperature and contact time up to the critical values ( T2 = 220°C, n2 = 9 turns) change the structural parameters and, consequently, any modifications influence changes in the mechanical properties of the threads. Namely, a higher treatment temperature and contact time increases the degree of crystallinity, the birefringence, and the maxima of the loss tangent and loss modulus temperature, and a significant increase in the breaking tenacity, elastic modulus and the thread’s tension at the yield point, and a decrease of the breaking extension is achieved. The observed deterioration of the thread’s mechanical properties above the critical treatment conditions is attributed to the destructive phenomena of the supra-molecular structure, resulting in an imperfect structure of the thread’s filaments.

Distortion in 100Cr6 and nanostructured bainite

A series of experiments on 100Cr6 and a nanostructured carbide-free bainitically transformed steel are performed. The effect of heat treatment conditions on the degree of distortion due to phase transformation is established. By transforming bainitically other than martensitically, cooling rate plays a major role in decreasing distortion by one order of magnitude in 100Cr6. Additional distortion reductions are possible by further decreasing the cooling rate when forming nanostructured carbide-free bainite. By invoking thermodynamic calculations and employing a neural network, it is shown that distortion can be engineered. When large amounts of retained austenite are present (such as the case of nanostructured bainite), this can be used to accommodate distortion. Additionally, it is possible to balance the expansion due to bainite formation with the contraction due to stress relaxation by controlling the amount of retained austenite. Exploitation of those mechanisms may aid in reducing distortion as a result of phase transformation (dimensional change) during the manufacturing of heat treated components.

Effect of heat treatment on the magnetic behaviour of powder steel 50Ni2Mo under uni-axial tension

In this study, investigation results on the effect of heat treatment conditions on the mechanical properties, internal stresses, magnetic characteristics, and electrical resistivity of powder steel 50Ni2Mo are presented. Coercive force and maximum magnetization are shown to be applicable as magnetic test parameters to reveal underheating for quenching. Heating for quenching above the critical point [Formula: see text] up to 910°С has an insignificant effect on the mechanical characteristics of the steel tested. It has been demonstrated that the use of the coercive force measured on minor magnetic hysteresis loops is preferable when estimating the level of applied tensile stresses in heat-treated powder steel 50Ni2Mo.

The preparation of c-axis epitaxial Bi-2212 films on STO(1 0 0) by sol–gel method

Bi 2Sr 2Ca 1Cu 2O 8+ δ (Bi-2212) films were grown on (1 0 0) oriented SrTiO 3 (STO) substrate using sol–gel spin-coating method. The effects of heat treatment conditions and coating times on the phase formation and surface morphology were investigated using thermal analysis, optical microscope, X-ray diffraction, and scanning electronic microscopy. Mixed phases were formed from 820 to 840 °C, and Bi-2212 single phase was obtained at 830 °C for 3 h. c-axis epitaxial films with smooth surfaces were obtained by drying at 600 °C and coating for 5 times.

Effects of Heat Treatment Condition on Properties of Strontium Barium Niobate Based Glass-Ceramic for Energy Storage Capacitors

Strontium barium niobate-based glass-ceramics are prepared by melt-casting followed by controlled crystallization. Results show that Ba0.25Sr0.75Nb2O6 with tungsten bronze structure forms as the dielectric phases from the glass matrix at 800°C. However, a secondary phase NaSr1.2Ba0.8Nb5O15 occurrs when crystallization temperature exceeds 850°C. The glass-ceramics formed through controlled crystallization exhibit the excellent stability of the temperature and frequency dependence of dielectric properties. The breakdown strength increases with the crystallization temperature. The glass-ceramic material heated at 800°C/3h+950°C/3h shows a breakdown strength of 1400 kV/cm and its energy storage density can reach up to 4.0 J/cm3, which may be strong candidate for high energy density storage capacitors for portable or pulsed power applications.

Preparation, characterisation and activity evaluation of CaCO3/ZnO photocatalyst

The photocatalyst CaCO3/ZnO with high activity was prepared by coprecipitation method using (NH4)2CO3, Zn(NO3)2 and Ca(NO3)2 as raw materials. The photocatalyst was characterised by X-ray powder diffraction, terephthalic acid photoluminescence probing technique (TA-PL), UV–vis diffuse reflectance spectroscopy and the fluorescence emission spectra. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic oxidation of methyl orange and rhodamine B. The results showed that the photocatalytic activity of the photocatalyst was much higher than that of pure ZnO. The best mole ratio of Ca/Zn in the sample was 1 : 2, and its intensity of TA-PL was the strongest. The effect of heat treatment condition on the photocatalytic activity of the photocatalyst was investigated. The best preparation condition was about 650°C for 7 h. Compared with pure ZnO, the photoabsorption wavelength range of the CaCO3/ZnO extends towards visible light and improves the utilisation of the total spectrum. The possible mechanisms of influence of CaCO3 on the photocatalytic activity of CaCO3/ZnO were also discussed.

Effect of heat treatment conditions on the morphology of structural components of clad high-speed steel

Research results of the heat treatment conditions' effect on the constituent morphology of the overlaid high-speed steels P18 and P6M5 are covered.

Failure criterion for aluminium tubes during warm hydroforming and in crash applications

A quantitative failure criterion was developed for aluminium (Al) tubes. The developed criterion is based on the critical damage value as calculated from the Cockroft and Latham ductile failure criterion and can be used to determine the forming limit during warm hydroforming or for failure during a crash. As-extruded, fully annealed, and T6-tempered Al 6061 tubes were tested to evaluate the effect of heat treatment conditions and forming temperature. To assess the formability of the Al 6061 tubes, uniaxial tensile tests and hydraulic bulge tests were performed in the temperature range of 25—300°C. The measured flow strength was used in finite element (FE) simulations for the tube hydroforming process. A commercial finite element method (FEM) code, DEFORM2DTM, was used to calculate the damage values and strains at various locations in the hydroformed tube. Based on the results of both the experimental and FEM analysis, a failure criterion, which is based on the forming limit and ductile fracture criterion, was developed. Using the critical damage value as a quantitative measure, the formability and also the critical damage value of the as-extruded tube is 50 per cent lower than that of the fully annealed tube. The developed failure criterion predicts well the observed failures during hydroforming for a hexagonal-shaped prototype part. Moreover, the failure criterion can be used to predict the crash performance of the hydroformed part, which has variations in the amount of prior deformation and in thickness. The benefit of the proposed failure criterion is that it can be used to predict both the forming limit of the tube during hydroforming and the behaviour of hydroformed tubes during a crash.

Effect of Heat Treatment Conditions on Shape Control of Large-sized Elongated MnS Inclusions in Resulfurized Free-cutting Steels

Effect of heat treatment conditions on shape evolution of large-sized elongated MnS inclusions in resulfurized free-cutting rolled steel has been investigated using confocal scanning laser microscope and Si2Mo resistance furnace. The results show that the heating rate, soaking temperature and soaking time impose significant effects upon shape profiles of elongated MnS. The split of slender MnS was oberved in continuous heating with heating rate in the range of 0.5–2 K/s. In addition, split degree of MnS indicated a negative relation with the rise of heating rate. As a result, separation of elongated MnS was not observed at the heating rate of 6 K/s. During soaking experiments, there was no remarkable shape change for MnS at temperature lower than 1073 K. While the elongated MnS splited up and spheroidized obviously at 1473 K. Correspondingly, number density of inclusions increased while mean length reduced as the soaking time increased from 1 h to 4 h at 1473 K. Significant shape change from slender to spindlelike or spherical was identified only when the soaking time exceeds 3 h or 4 h. Based on the Gibbs Thompson relation and the obtained experimental results, mechanism of shape evolution of MnS inclusions was discussed and morphology evolution of MnS was divided into three major steps: (1) first, the shrinkage occurred in the longitudinal direction at the beginning of heating process, (2) expansion and contraction in radial direction followed after the shrinkage which caused the split of slender MnS; (3) eventually, the spherical particles emerged from the split parts.

Microstructure and Crystallization of MAS Glass-Ceramics Containing Alkali Oxides

MgO-Al2O3-SiO2 glass-ceramics containing 4.0w% alkali oxides were prepared by conven- tional melt quenching technique. The effects of heat treatment conditions on crystal types, microstructure and break strength of the glass-ceramics were studied by DSC, XRD, SEM and break strength tests. The main crystallization phases of this glass system are β-quartz (Li2-2xMgxAl2Si3O10) and β-Spodumene, no cordierite phase found. The glass-ceramics possessed a regular network-shaped microstructure feature formed by pyroxene crystals. With the increase of temperature, the β-Quartz around pyroxene crystals converted into β-spodumene and the regular network-shaped microstructure feature getting weaker and disappeared. The average break strength of the glass-ceramics containing no cordierite crystals based on MgO2-Al2O3-SiO2 system is about 150MPa, which is much high than the base glass.

Effect of heat treatment conditions on the structure and mechanical properties of a cast Al-Li-Cu aluminum alloy

Quenching and one- and two-stage aging conditions are found for a high-strength Al-Li-Cu cast alloy with a low density from the results of studying its structure, mechanical properties, and aging kinetics.

Effect of Heat Treatment Conditions on Microstructure and Infrared Transmission Property of Germanate Oxyfluoride Glass-Ceramics

Germanate oxyfluoride glass in CaF2/BaF2-AlF3-SiO2-GeO2 was prepared by melt quenching technique and subsequently converted to glass-ceramics with microstructures comprised nano-crystallites in a residual glass matrix by two-step heat treatments process. DSC, XRD, SEM and IR transmission investigations were used to determine structural characteristics and optical property of the prepared germanate oxyfluoride glass-ceramics. The influences of heat treatment conditions on crystallization behaviors and infrared transmission were discussed. The results show that crystal phase in the glass-ceramics is only Ge2Al6O13 and the crystal size is about 20nm-80nm when treated temperature ranges from 900 oC to 960oC. Good transparency is exhibited in visible light band to midinfrared band (5.0um) when treated temperature is low than 940 oC.

Effect of heat-treatment conditions on structural and phase transformations in a two-phase α + β titanium alloy subjected to thermomechanical treatment

Effect of heat-treatment parameters (heating temperature in a range of 550 to 700°C and holding time from 0.5 to 2 h) on the occurrence of structural and phase transformations in the Ti-6-4 Eli titanium alloy, which was preliminarily subjected to warm rolling at 550°C after quenching from 945°C, has been studied. During the heating of the rolled alloy to 550°C, the formation of recrystallized nanosized grains in the martensitic matrix was found to occur. The increase in the temperature and time of holding favors the activation of recrystallization processes and increase in the size of arising grains to a micron level. It has been found that the decomposition of the α′ martensite can occur at the expense of both the precipitation of nanosized β-phase particles via a heterogeneous mechanism (T h = 550–600°C) and through the formation of individual β-phase grains between recrystallized α′ particles at the higher heating temperatures (650–700°C). The prevalence of one of these processes, namely, recrystallization or decomposition, during the heat treatment of the deformed alloy determines the character of changes of microhardness characteristics.

Effect of heat treatment on the mechanical properties of North American jack pine: thermogravimetric study

Heat treatment improves dimensional stability of wood, reduces its decay, and darkens its color. However, mechanical properties of wood can deteriorate during the heat treatment. The effect of heat-treatment conditions (maximum treatment temperature, heating rate, exposure time at the maximum heat-treatment temperature, and the gas humidity) on the mechanical properties of North American jack pine (Pinus banksiana) was studied using thermogravimetric analyzer. This type of study permits the identification of the best treatment conditions which will minimize reduction of mechanical properties of jack pine. The results showed that the degree of change in bending strength, hardness, screw withdrawal strength, and dimensional stability of jack pine during heat treatment depends strongly on the treatment conditions used. Therefore, great care should be taken to select the treatment conditions. Thermogravimetric analysis can be used as a first step for selection.

Depletion of CO oxidation activity of supported Au catalysts prepared from thiol-capped Au nanoparticles by sulfates formed at Au–titania boundaries: Effects of heat treatment conditions on catalytic activity

We have investigated the effects of heat treatment in air and H 2/Ar on Au/titania-coated silica aerogel catalysts prepared through adsorption of thiol-capped Au nanoparticles (AuNPs). Sulfur atoms remained on the support surfaces in the form of sulfates upon calcination at temperatures below 773 K. X-ray absorption fine structure and in situ infrared absorption measurements of the catalysts suggested that some of the sulfates affected the catalytic properties of the AuNPs through the interactions between AuNPs and sulfates. The turnover frequency for CO oxidation reaction of the catalysts was enhanced by a factor of 3–5 upon the removal of the sulfates through calcination at 873 K or H 2/Ar treatment at 673 K after calcination at 673 K. These results reveal the importance of the contribution of Au–support interfaces to the CO oxidation efficiency on Au/TiO 2 catalyst systems.

Effect of Heat Treatment Conditions on the High Temperature Deformation of 6082-Al Alloy

High-temperature deformation of an artificially aged 6082-Al alloy was conducted in the present investigation. Tensile tests were carried out at temperatures of 623, 673 and 723 K at various strain rates ranging from 5x10-5 to 2x10-2 s-1. The behavior of the alloy is characterized by high stress exponent, n and high apparent activation energy, Qa that are higher than what is usually observed in Al and Al solid-solution alloys under similar experimental conditions, which implies the presence of threshold stress; this behavior results from dislocation interaction with second phase particles. The threshold stress, σo values were seen to decrease exponentially with temperature. By incorporating the threshold stress in the analysis, the true activation energy, Qt was calculated to be close to that of dislocation pipe diffusion in Al. Analysis of the experimental data of the alloy in terms of the Zener- Hollomon parameter vs. normalized effective stress, revealed a single type of deformation behavior with an n value of ~7. Measurements showed that the values of elongation percent at failure increase with strain rate and temperature.

Aging behavior of a 2024 Al alloy-SiCp composite

In the present research work the 2024 aluminum alloy was reinforced with SiC particles via powder metallurgy method. The effect of heat treatment conditions on artificial aging kinetics was investigated. The solution treatment of the composite sample and the unreinforced alloy was carried out at 495 °C for 1, 2 and 3 h followed by aging at 191 °C for various aging times between 1 and 10 h. The existence of SiC particles led to increasing the peak hardness of the alloy. The peak hardness of the composite sample took place at shorter times than that of the unreinforced alloy for the samples solution treated for 2 and 3 h, but took place at longer times for the samples solution treated for 1 h. The suitable solution treating time was about 2 h for both the composite and the unreinforced alloy that led to the fastest aging kinetics and the maximum hardness. At the solution treating time shorter than 2 h due to incomplete dissolution of precipitates, the aging kinetics decelerated and the hardness values decreased. X-ray diffraction studies indicated the presence of precipitation phases such as CuAl 2 and CuMgAl 2 in the composite in both as-extruded and solutionized conditions. For the samples solution treated more than 2 h, hardness values decreased due to the grain growth of matrix but no change occurred in the aging kinetics.

Effect of heat treatment on performance of chlorine-resistant polyamide reverse osmosis membranes

In our series of studies for the development of a reverse osmosis polyamide membrane with high resistance to chlorine, N,N′-dimethyl-m-phenylenediamine ( N,N′-DMMPD) was selected in the preparation of the polyamide membrane after the screening of various diamines. High resistance to chlorine was confirmed for the prepared membrane in our previous work. However, the heat treatment conditions were not yet optimized. In this work, we focused on the effects of heat treatment conditions on the membrane properties. The heat treatment temperature and time remarkably influenced salt rejection and flux. Maximum rejection was found with respect to the temperature. Both rejection and flux showed trends to become constant with longer treatment times. However, rejection reached the constant value in less time than flux. Thus, to obtain both high rejection and flux, an optimum treatment time existed. The newly prepared polyamide membrane showed higher salt rejection than the previously prepared membrane while maintaining high resistance to chlorine.

Phase transformation and microstructure of MgO–Al2O3–SiO2 system glass–ceramics under different heat treatment conditions

Effects of heat treatment conditions on phase transformation, microstructure and thermal expansion coefficient (TEC) in MgO–Al2O3–SiO2 system glass–ceramics were investigated by means of differential thermal analysis, X-ray diffraction and scanning electron microscopy. The magnesium aluminium titanate (MAT) precipitated firstly at 850°C and β-quartz solutions (β-QSS) formed at 950°C. Further increasing temperature to 1000°C, MAT disappeared and β-QSS became master phase, following little amount of α-cordierite, MgTi2O5, rutile and sapphirine. When glass was treated at 1050°C, β-QSS content decreased and α-cordierite became master phase. As temperature reached higher than 1100°C, β-QSS and sapphirine disappeared, and α-cordierite became master phase accompany with rutile and MgTi2O5 as secondary phase. The microstructure transformed gradually from particle shape crystallites to slat shape network with the increase in heat treatment temperature. By controlling heat treatment condition, an ideal glass–ceramics with proper TEC for matching sealing to 4J29 alloy has been obtained.

Preparation and luminescence properties of Eu2+-doped CaSi2O2-dN2+2/3d phosphors

Eu2+-doped CaSi2O2-dN2+2/3d phosphors for white LED lamps were prepared by solid-state reaction, and the effects of heat-treatment conditions and the overall composition of host lattice on the optical properties have been discussed. Eu2+-doped CaSi2O2-dN2+2/3d displayed a single broad emission band peak at 540 nm, which could be assigned to the allowed transition of Eu2+ from the lowest crystal field component of 4f65d to 4f7 ground-state level. The excitation band of samples, extending from UV to blue, is extremely wide, so the phosphors are suitable for white LED lamps in combination with a UV or blue LED dies. The highest PL intensity is found for the sample sintered at 1400 °C. Moreover, the emission intensity decreases when N partially replaces O. A red shift of emission wavelength did not occur with increasing of the N content.