Effect Of Preliminary Heat Treatment Research Articles

Effect of Preliminary Heat Treatment on the Formation of Structure and Residual Stresses in the AMg6 Alloy at Laser Shock Peening Without Coating

Effect of Preliminary Heat Treatment on the Formation of Structure and Residual Stresses in the AMg6 Alloy at Laser Shock Peening Without Coating

Effect of Preliminary Heat Treatment on the Formation of Structure and Mechanical Properties of Brass during Alternating Bending

Effect of Preliminary Heat Treatment on the Formation of Structure and Mechanical Properties of Brass during Alternating Bending

Влияние предварительной термической обработки на морфологию углеродного слоя, формирующегося на поверхности хлорированного поливинилхлорида при воздействии мощного ионного пучка

The effect of preliminary heat treatment on the morphology of carbon layer formed on the surface of chlorinated polyvinyl chloride with the addition of ferrocene (10 % of polymer weight) under the impact of a high-power nanosecond-durable ion beam has been studied. Preliminary exposure of samples in an oven at different temperatures for 1 hour leads to partial dehydrochlorination of the surface layer of the polymer film and interchain crosslinking, creating centers for the start of the carbonization reaction, and thus affects the formation of carbon nanostructures during subsequent irradiation with a high-power ion beam. The possible mechanism of carbon nanostructures formation from chlorinated polyvinyl chloride under the impact of a high-power ion beam and the mechanism of the influence of preliminary heat treatment on it are considered. It has been established that different heat treatment temperatures lead to different morphologies of the resulting carbon nanostructures. On the control sample and the sample subjected to heating to 100 °C, only nanofibers are formed, preheating to 150 °C leads to the formation of a porous structure with nanosized pores under the nanofibers, and preheating to 200 °C leads to a significant decrease in the porosity and concentration of nanofibers.

Effect of Preliminary Heat Treatment on Deformation of Brass by the Method of ECAP

Effect of Preliminary Heat Treatment on Deformation of Brass by the Method of ECAP

Influence of Preliminary Heat Treatment and Ball Milling of Aluminum Powder on Cold Spray Process

This paper presents the results of a study of the effect of preliminary heat treatment and ball milling of aluminum powder on the cold spraying process and the properties of the obtained coatings (porosity and microhardness). The ball milling of aluminum powder leads to an increase in specific surface area, a decrease in apparent density and a decrease in the value of the crystallite size, which indicates a decrease in grain size. It is shown that coatings deposited from ball milled powders have slightly higher coatings hardness averagely. The profilometry of aluminum coatings obtained under the same conditions from the initial and processed powders did not reveal significant changes in the form of coatings and their typical dimensions (width, thickness), which indicates the absence of significant changes in the deposition coefficient of the initial and processed aluminum powders. Ball milled powders on average correspond to slightly higher hardnesses of coatings.

Effect of the Preliminary Heat Treatment of Chlorinated Polyvinyl Chloride on the Formation of Carbon Nanofibers on its Surface under High-Power Ion-Beam Irradiation

The effect of a high-power ion beam of nanosecond duration on layers of chlorinated polyvinyl chloride with a catalytic additive (ferrocene), which preliminarily underwent treatment in air or an inert medium in the temperature range 100–400°C, is studied. Heat treatment at 150°C for 1 h is shown to reduce the length of the formed carbon nanofibers by ~20 times. Disk-shaped depressions are observed on the surface of the polymer irradiated after treatment at 200°C due to the removal of a part of the surface layer. These depressions are likely associated with polymer embrittlement during heat treatment. A net-like structure is observed between these depressions. An increase in the treatment temperature to 400°C (in an inert medium) results in the formation of nanofibers with a length not exceeding 0.5 μm. The effect of preliminary heat treatment on the growth of carbon nanofibers and possible mechanisms of their growth under the influence of a high-power ion beam on a chloropolymer containing a catalytic additive is discussed.

The effect of preliminary heat treatment on the durability of reaction bonded silicon nitride crucibles for solar cells applications

Silicon nitride crucibles have the potential to replace silica crucibles and reduce the cost of silicon crystallization because of their reusability potential. Till date, crucibles’ heat treatment before each use is a prerequisite to achieve non-wetting conditions that is needed to facilitate the ingot release and hence enable reusability. Yet, no studies have examined the heat treatment influence on the crucibles’ durability. The present investigation focuses on the crucibles’ heat treatment and its impact on the crucibles’ lifetime. Repeated heat-treatments of silicon nitride crucibles in the air at above 1100 °C leads to crucible fracture. Therefore, this study identifies the cause and the mechanism of such failures by applying different heat treatment procedures in the air. The mass gain and the oxidation rates of the crucibles at different temperatures are measured via Thermogravimetry (TG) and Differential Thermal Analyzer (DTA). The results show that the porosity and phase distribution along the crucible wall thickness, play a key role in the crucible’s behavior during oxidation. Moreover, excessive internal oxidation in the tested crucibles results in severe thermal stresses which cause cracking during cooling.

Влияние предварительной тепловой обработки сырья на химический состав и антиоксидантную активность овощного пюре

Исследуются технологические режимы производства овощного пюре: бланширование в горячей воде, бланширование острым паром (шпарение). Авторами изготовлены опытные образцы согласно технологическим параметрам: для бланширования температура воды составляла 85-100°С (10-15 мин), для шпарения температура пара составляла 105-110°С (5-10 мин). Цель исследования – изучение влияния предварительной тепловой обработки овощного сырья (бланширование и шпарение) на химический состав и антиоксидантную активность готового продукта – пюре. В экстрактах анализируемых образцов определялись фенолы, флавоноиды, антиоксидантная активность по методам DPPH (2,2-дифенил-1-пикрилгидразила) и FRAP (железо-восстанавливающая антиоксидантная способность). Результаты исследования показали, что более щадящим для определяемых показателей является технологическая операция – бланширование при температуре 85-100°С в течении 10-15 мин. При этом лидером по большинству параметров выступает свекольное пюре.

Effect of preliminary heterogenization on the structure and hardness of cryorolled aluminum alloy D16

The effect of preliminary heat treatment on transformations of the grain structure of the aluminum alloy D16 under isothermal rolling at the temperature of liquid nitrogen and subsequent annealing was investigated. It was found that heterogenization by intensifying the nucleation of new grains facilitates the nanostructuring of the alloy during cryorolling, as well as the formation of a fine-grained structure upon static recrystallization at post-deformation annealing.

Effect of Initial Structural State on Formation of Structure and Mechanical Properties of Steels Under ECAP

The effect of preliminary heat treatment and equal-channel angular pressing (ECAP) in a stage die on the microstructure and mechanical properties of steels 45 and 35KhM is studied. The grain size, the microhardness, and the strength and ductility characteristics of the steels after the ECAP are determined. The suggested modes of thermomechanical treatment improve the combination of the properties of the steels studied.

Структура ультрамелкозернистого сплава А2024 при комбинированной термодеформационной обработке

The present work studies the effect of preliminary heat treatment on the features of ultra fine-grained (UFG) structure formation in Al-Cu-Mg alloy by means of high pressure torsion in Bridgman anvils. Heat treatment was carried out following two regimes: regime 1 included heating to a temperature of 500°C, 16 hours and quenching in water, and regime 2 additionally included two-stage T6I6 aging: 120°C, 1.5 hours and 160°C, 6 hours, after quenching with water quenching after each stage. The number of revolutions of the anvil was n = 5, 10, which, according to the calculation, corresponded to the true logarithmic strain e ≈ 5.5, 6.5. It is shown that after the preliminary two-stage aging T6I6 of coarse-grained alloy fragmented grain / subgrain structure with high dislocation density was formed at e = 5.5. The relaxation processes were suppressed by blocking of the grain boundaries by dispersed particles of the strengthening S phase. It was shown that at e = 6.5 alloy structure is refined to the nanolevel, and the process of dynamic dissolution of S phase precipitates started parallel. It is accompanied by the appearance of defect-free grains and a mixed structure was formed. In the case of the torsion of hardened coarse-grained alloy, the main mechanism of grain refinement to 450 nm is dynamic recrystallization. At e = 6.5 the dynamic aging of the supersaturated Al solid solution becomes the additional relaxation channel of the elastic energy and the hardness of the UFG alloy increases up to 3000 MPa.

The effect of alloying with hafnium on the thermal stability of chromium bronze after severe plastic deformation

The effect of alloying with 0.9 wt% hafnium on the thermal stability of the Cu-0.7%Cr alloy after severe plastic deformation by high pressure torsion has been studied by microhardness and resistivity measurements, optical microscopy, and transmission electron microscopy. The data obtained were used to construct the curves of the temperature dependences of microhardness and resistivity for the alloy samples in a temperature range of 50–550 °C and the curves of the microhardness distribution over the sample diameter. The effect of preliminary heat treatment on the stability of the structure formed upon deformation is considered. It is shown that alloying with hafnium decreases the grain size from 250 to 120 nm, increases the strength, and elevates the temperature of the beginning of alloy softening upon heating. In addition, the introduction of hafnium to the alloy results in the occurrence of aging upon heating, and the strength reaches maximum (3177 MPa) at a temperature of 450 °C.

Structure and mechanical properties of medium-carbon steels after heating in the intercritical temperature range

The effect of preliminary heat treatment (quenching or normalizing) on the microstructure and mechanical properties of medium-carbon steels 24KhGBR, 37G2S and 37KhGF after a hold in the intercritical temperature range (ITR) and air cooling is studied. It is shown that the preliminary heat treatment (especially the quenching) affects positively the combination of mechanical properties obtained after heating in the ITR.

Effect of Preliminary Heat Treatment on the Stability of Austenite in Steel 08Kh15N5D2T

The effect of the heating rate and long-term holds in the temperature range of inverse martensitic (α → γ) transformation on the stability of austenite in the cooling of chromium-nickel steel 08Kh15N5D2T is studied. Additional conditions for growth of stable austenite in the structure of the steel (to 60%) are determined. Isothermal diagrams of decomposition of retained austenite at negative temperatures after annealing in the (α + γ) range in different modes are plotted.

Effect of Initial Microstructure of Tool Steels on the Thickness and Hardness of Layers Obtained by Nitrocarburizing

The effect of preliminary heat treatment on the microstructure and kinetics of formation of the hardened layer in the process of subsequent nitrocarburizing of steels A681 (ASTM), Kh12M (GOST), Kh12FS (GOST), 6437E (AMS), and X46Cr13 (BS) is studied. Preliminary treatment of two kinds, i.e., annealing and quenching with tempering, is considered. The thermochemical processes are performed in a solid carburizer (powder) at 500°C for 4 h. The thickness, hardness, microstructure, and phase composition of the resulting layers are determined.

Preparation of Boron Nitride Fibers Using Hydrated Cellulose. Part 3. Nitriding Hydrated Cellulose Fibers Impregnated with Boric Acid

The effect of preliminary heat treatment (PHT) for hydrated cellulose fibers impregnated with boric acid on the composition and structure of nitrided products is studied. Subsequent nitriding after PHT in helium leads to formation of carbon fibers coated with boron nitride, but after PHT in air there is formation of hexagonal and rhombohedral boron nitride powder. Data obtained are compared with results reported previously.

Preparation of boron nitride fibers with the use of hydrated cellulose. II. Nitriding hydrated cellulose fibers impregnated with ammonium borate

The effect of preliminary heat treatment (PHT) of hydrated cellulose fibers impregnated with an ammonium tetraborate solution on the composition and structure of nitrided products was studied. The PHT conditions which upon subsequent nitriding led to the formation of C—BN fibers with a coating of BN, and also hollow and solid BN fibers, were determined

Effect of preliminary heat treatment on the microstructure and resistance to brittle fracture of high-strength steels

In many cases the plastic properties and brittle fracture strength of industrial semiproducts from high-strength steels are caused by their structural inhomogeneity. The structural inhomogeneity of such steels can be diminished and the plastic characteristics improved by conducting a preliminary heat treatment. The present paper concerns the results of a study of the effect of such heat treatment on the properties and the microstructure of high-strength steels.

Two-step nucleation in lithium disilicate glass

The effect of preliminary heat treatment on the kinetics of nucleation is modeled by numerical solution of the kinetic equations within the framework of standard nucleation theory. It is shown that such an approach sufficiently exactly explains the measured data of the number of nuclei for two-step annealing treatments in a Li2O · 2SiO2 melt. The measured increase of the nucleation rate after the preliminary heat treatment is ascribed to the increase of the frequency of attachment of single molecules on the nucleus surface after the temperature change.

Crystallization effect after preliminary heat treatment in MgOAl2O3SiO2 quenched glass

The effect of preliminary heat treatment (PT) of a quenched glass in the vitrification temperature range on the course of subsequent non-catalyzed crystallization is studied using the X-ray and pycnometer density measurements for glassy stoichiometric cordierite powder. An increase of crystallized μ-cordierite quantity after PT is found. It is established that this effect is caused by the ≈20% lowering of the activation energy of μ-phase formation due to the structural relaxation process taking place in quenched glass during PT. A qualitative model to explain the effect observed as a result of an interaction between defects in the initial quenched glass is proposed.