scholarly journals OPTIMIZATION OF SYNTHESIS PROCESS OF NANOSTRUCTURED CARBIDE-CORUNDUM SILUMIN MODIFIER

2021 ◽  
Vol 1 (54) ◽  
pp. 71-79
Author(s):  
Dmitry V. ORDA ◽  
Keyword(s):  
Mathematical Model ◽  
Titanium Carbide ◽  
Response Function ◽  
Isothermal Holding ◽  
Holding Time ◽  
Synthesis Process ◽  
Synthesis Parameters ◽  
Response Equation ◽  
Main Factors ◽  
Holding Temperature

A mathematical model is developed for the process of synthesis of nanostructured modifier TiC-Al2O3 by gasphase deposition based on the system of starting materials TiO2-Al-C. To construct the response equation in the form of a polynomial of the second degree, the experiments were carried out in accordance with the model of a rotatable composite plan of the second order with three factors, including 20 experiments. The main factors considered were the isothermal holding temperature T (°C), the isothermal holding time t (s), and the proportion of the chlorinating component Q (wt.%), and as a response function — the proportion of titanium carbide q(TiC) (wt.%) in the composition of the synthesized modifier. The paper describes the results of computational and experimental modeling, from which it can be concluded that to obtain a modifier with the highest content of titanium carbide, the synthesis parameters should be as follows: T = 900–930 °C; t = 2–2.5 h; Q = 4–4.5 wt.%. The resulting TiC-Al2O3 modifier contains 34 wt.% TiC and has a nanostructured structure, with spherical and filamentous particles which diameter does not exceed 100 nm.

Microstructural Evolution of AZ31 Mg Wrought Alloy during Partial Remelting for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 251-254
Author(s):  
Young Ok Yoon ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Grain Sizes ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

An attempt has been made to investigate feasibility of thixoextrusion for AZ31 Mg wrought alloy through simple partial remelting. Microstructural evolution of AZ31 Mg wrought alloy for thixoextrusion was investigated as functions of isothermal holding temperature and time in the partially remelted semisolid state. The interesting point of this study was that the thixotropic structures of AZ31 Mg wrought alloy without additional pretreatment could be obtained through simple partial remelting. The uniform average grain size and liquid fraction according to the isothermal holding time were very important for the thixoextrusion. Because, it is must be considered on actual extrusion time. The liquid fraction was increased with increasing isothermal holding temperature and time. But, the liquid fraction was almost uniform after 10 min. The average grain size was decreased with increasing isothermal holding temperature. On the other hand, as the holding time increased, the average grain sizes were uniform at 615 and 622. This phenomenon is very useful for thixoextrusion in terms of process control such as actual extrusion time.

Effect of Isothermal Holding in Solid-Liquid Phase Region on Mg2Si Morphology in Hypereutectic Al-Si In Situ Composite

2012 ◽  
Vol 430-432 ◽  
pp. 711-714
Author(s):  
Zheng Liu ◽  
Hong Biao Xu ◽  
Kai Cao ◽  
Mei Yan Huang
Keyword(s):  
Liquid Phase ◽  
Shape Factor ◽  
Isothermal Holding ◽  
Phase Region ◽  
Holding Time ◽  
In Situ Composite ◽  
Size And Morphology ◽  
Solid Liquid ◽  
Holding Temperature

Mg2Si reinforced hypereutectic Al-Si in-situ composite was prepared and the effects of the isothermal holding temperature and time on Mg2Si in the composite were researched. The results showed that there were the important effects of holding temperature and time in the solid-liquid phase region of the Al-Si alloy on the size and morphology of Mg2Si. The size and morphology of Mg2Si became smaller and round with the rising of the holding temperature and prolonging of the holding time. The suitable technology in the test was obtained, in which when being held at 615°C for 300s, the size of Mg2Si decreased to 20.54μm and the shape factor of Mg2Si reached about 0.67.

Effects of cooling rate and isothermal holding on the characteristics of MnS particles in high-carbon heavy rail steels

2020 ◽  
Vol 117 (1) ◽  
pp. 110 ◽  
Author(s):  
Xuewei Zhang ◽  
Caifu Yang ◽  
Lifeng Zhang
Keyword(s):  
Cooling Rate ◽  
Isothermal Holding ◽  
Average Diameter ◽  
Holding Time ◽  
Area Fraction ◽  
Air Cooling ◽  
Steel Matrix ◽  
Number Density ◽  
3D Morphology ◽  
Holding Temperature

The characteristics of MnS particles were intensively investigated at three different cooling rate of 80.4 K · s−1 (water cooling), 3.8 K · s−1 (air cooling) and 1.8 K · s−1 (furnace cooling) as well as the different isothermal holding temperature and time in laboratory experiments. The three-dimensional (3D) morphology of MnS particles was extracted from steel samples using non-aqueous solution electrolysis. The results showed that the 3D morphology of MnS changed from a nearly spherical into rod-like and the area fraction and average diameter of MnS increased with decreasing cooling rate. During isothermal holding process, the morphology of MnS changed little at 1473 K (1200 °C), but their shape profiles varied from a nearly spherical and spindle-like to irregular at higher holding temperature 1673 K (1400 °C) when the holding time exceeded 60 min. Moreover, the number density and area fraction of MnS decreased with increasing holding time at 1573 K (1300 °C) and 1673 K (1400 °C), respectively. Especially at 1573 K (1300 °C), the 1 ∼ 3 µm MnS inclusions were dissolved and lead to decreasing of number density, but that > 3 µm one occurs growth and resulted in increasing of average diameter. The calculation results show that the starting temperature of precipitation of MnS was about 1627 K (1354 °C) and effect of cooling rate on the segregation of Mn and S is insignificant. Considering the segregation of solutes, MnS formation and growth takes place in the solid/liquid interface of steel when the solid fraction is close to 0.9567 during solidification. It has been found that the increase of cooling rate gives rise to the decreased of MnS diameter because the growth time of MnS is short. Furthermore, thermodynamic calculations of MnS solid solubility product were carried out to reveal the high holding temperature and long holding time favors the dissolution of MnS particles. It is necessary to decrease the sulfur content by less than 16 ppm in order to assure that the larger MnS which formed during solidification redissolves in the steel matrix, rather than relying on increasing the heating temperature which is above 1649 K (1376 °C). Subsequent, the MnS will precipitate again in a finely dispersive state during rolling process, and it can hinder annealing grain growth and finally make for the improvement of the toughness property of the steel.

Effect of Partial Remelting Procedure on the Microstructural Evolution of 7075 Al Wrought Alloy for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 336-339 ◽  
Author(s):  
Hyung Ho Jo ◽  
Young Ok Yoon ◽  
Jin Kyu Lee ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Feasibility Study ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

The feasibility study for thixoextrusion of 7075 Al wrought alloys was carried out with respect to reheating profile, isothermal holding temperature and time during the partial remelting through simple partial remelting. The reheating rates were 40/min and 60/min. The isothermal holding temperatures were controlled at 609, 622, 628 and 632 for 0, 2, 5, 10 and 30 min. The interesting point of this study was that the thixotropic structures of 7075 Al wrought alloy without additional pretreatment could be obtained through simple partial remelting. The average grain size was significantly smaller in the quickly heated specimen. The liquid fraction was increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min is considered very useful for thixoextrusion in terms of actual extrusion time.

scholarly journals Crystallization and Mechanical Properties of Polypropylene under Processing-Relevant Cooling Conditions with respect to Isothermal Holding Time

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Christopher Fischer ◽  
Dietmar Drummer
Keyword(s):  
Mechanical Properties ◽  
Isothermal Holding ◽  
Holding Time ◽  
Crystal Modification ◽  
Time Behavior ◽  
Scanning Calorimetry ◽  
Ordered Structures ◽  
Roll Temperature ◽  
Temperature Time ◽  
Holding Temperature

For semicrystalline thermoplastics, aside from pressure and shear, the temperature-time behavior while cooling the melt significantly affects the geometry and degree of ordered structures (e.g., spherulite size, degree of crystallization, and crystal modification) and, as a consequence, the resulting global component properties. Previous research has shown that a higher isothermal holding temperature (e.g., mold temperature and chill-roll temperature) leads to the formation of more distinct ordered structures and, therefore, can lead to greater stiffness and strength. Nevertheless, isothermal holding time during manufacturing is typically not taken into account. In this paper, fast scanning calorimetry (FSC) measurements were taken using polypropylene to analyze the crystallization during idealized temperature-time profiles based on the dynamic temperature process and to investigate the crystallization behavior at different temperatures and isothermal holding times analytically. Furthermore, iPP foils were extruded and tested mechanically to investigate the knowledge gained experimentally. Analytical and mechanical results show that foils produced at the same isothermal holding temperature can obtain significantly different ordered structures and mechanical properties depending primarily on the isothermal holding time.

Investigation of Temperature Deformations and Burning of Models from Polymers

2021 ◽  
Vol 316 ◽  
pp. 40-45
Author(s):  
Aksaule A. Mamayeva ◽  
Akerke T. Imbarova ◽  
Marzhan T. Chukmanova
Keyword(s):  
3D Printing ◽  
Isothermal Holding ◽  
Printing Technology ◽  
Temperature Expansion ◽  
3D Printing Technology ◽  
Linear Dimensions ◽  
Temperature Deformations ◽  
Thin Walled ◽  
Subsequent Decomposition ◽  
Holding Temperature

The usage of 3D printing technology SLA and DLP is promising for obtaining casting models. The article presents the results of a study of temperature deformations, developing during the burning of models from polymers “Fun to Do Castable Blend”, “Oh-All! Red” and “Orange Fluor”. In the performance of the experiments, photopolymer models were exposed to an impact of isothermal at temperatures from 50 to 330 °C, and their linear dimensions measured; changes developing on their surface were noted. It is shown that, with an increase of the isothermal holding temperature, the models expand first and narrow later. It has been linked to temperature expansion and subsequent decomposition of the photopolymer. It is shown that the casting molds ,obtained with the usied thin-walled hollow casting models from these photopolymers, are destroyed at the stage of their burning.

Properties of ZrO2–Al2O3 composite as a function of isothermal holding time

2007 ◽  
Vol 25 (5-6) ◽  
pp. 374-379 ◽  
Author(s):  
J.K.M.F. Daguano ◽  
C. Santos ◽  
R.C. Souza ◽  
R.M. Balestra ◽  
K. Strecker ◽  
...  
Keyword(s):  
Isothermal Holding ◽  
Holding Time ◽  
Al2o3 Composite

scholarly journals Calculation of productivity of multi-section trawls for extraction of ferromanganese nodules

2020 ◽  
Vol 177 ◽  
pp. 03010
Author(s):  
Maxim Rakhutin ◽  
Alexey Kashirsky ◽  
Yuliya Lagunova
Keyword(s):  
Mathematical Model ◽  
World Ocean ◽  
Ferromanganese Nodules ◽  
The World ◽  
Main Factors

A mathematical model of the operational productivity of trawls for the extraction of ferromanganese nodules from the bottom of the World Ocean is proposed. On the example of the previously proposed cassette trawl, the analysis of the influence of the main factors on the value of operational productivity is carried out.

scholarly journals Air pollution: smog and fog in the large cities of Ukraine.

2017 ◽  
Vol 1 (1) ◽  
pp. 1-12
Author(s):  
Rostyslav Sipakov
Keyword(s):  
Mathematical Model ◽  
Air Pollution ◽  
Chemical Kinetics ◽  
Gaseous Pollutants ◽  
Scattering Process ◽  
Large Cities ◽  
Sample Contamination ◽  
Factors Of Influence ◽  
Main Factors ◽  
Harmful Substances

The main factors of air pollution in large cities in Ukraine are described in the article and the main factors of smog have been analyzed on the example of Kyiv in the period January - February 2017. For the analysis of sample contamination points in Kyiv, we used a mathematical model of the spread of solid and gaseous pollutants with the main factors of influence on the scattering process of contaminants in the air: heat, turbulence, chemical kinetics, etc. As a result of the simulation it was confirmed that the smog in Kyiv and surroundings was formed as a result of anticyclone and air pollution by harmful substances, soot and etc.

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