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.

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.

Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route

2006 ◽  
Vol 510-511 ◽  
pp. 362-365 ◽  
Author(s):  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Jin Kyu Lee ◽  
Dong In Jang ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
High Strength ◽  
Industrial Applications ◽  
High Productivity ◽  
Die Life ◽  
Average Grain Size ◽  
Low Energy Consumption ◽  
Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al wrought alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al wrought alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.

Influence of Reheating Profile on Microstructural Evolution of 2024 Al Wrought Alloy for Thixoextrusion

2007 ◽  
Vol 544-545 ◽  
pp. 371-374
Author(s):  
Dong In Jang ◽  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Low Energy ◽  
Billet Temperature ◽  
High Productivity ◽  
Main Emphasis ◽  
Average Grain Size ◽  
Low Energy Consumption ◽  
Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure and cost saving because of the low energy consumption compared with the conventional extrusion processes. For the thixoextrusion, the low liquid fraction (fL<0.3) should be achieved and also the liquid fraction and average grain size should be uniform according to the reheating profile at the desired low liquid fraction. The main emphasis of this study is to investigate the feasibility of thixoextrusion for 2024 Al wrought alloy without additional pretreatment. The results show that the liquid fraction and average grain size were almost uniform with respect to isothermal holding temperature and time. It was very useful for thixoextrusion in terms of process control such as billet temperature control and actual extrusion time.

Remelting Technology and Microstructural Evolution of Semi-Solid Al-7Si-2RE Alloy

2010 ◽  
Vol 33 ◽  
pp. 1-5
Author(s):  
Shi Kun Xie ◽  
Rong Xi Yi ◽  
Xiu Yan Guo ◽  
Xiao Liang Pan ◽  
Xiao Qiu Zheng
Keyword(s):  
Aluminum Alloy ◽  
Microstructural Evolution ◽  
Temperature Control ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Control Program ◽  
Holding Time ◽  
Α Phase ◽  
Semi Solid ◽  
Equiaxed Grains

In semi-solid remelting process, the various stages of reheating temperature and isothermal holding time must be accurately controlled in order to obtain the uniformly distributed and small equiaxed grains microstructure. In this paper, a temperature control program was developed and the remelting process for Al-7Si-2RE aluminum alloy was carried out. The results showed that with the raise of reheating temperature and the extension of isothermal holding time, the liquid fraction increases, α-phase grain grows and becomes rounding in the process of Al-7Si-2RE alloy semi-solid remelting. The most reasonable process parameter of reheating temperature is at 585~590°C and its appropriate isothermal holding time are about 10~15min for the semi-solid Al-7Si-2RE alloy.

Microstructural Evolution of SiCp/AZ61 Composites during Partial Remelting

2008 ◽  
Vol 141-143 ◽  
pp. 545-549 ◽  
Author(s):  
Hong Yan ◽  
Fa Yun Zhang ◽  
Wei Pan
Keyword(s):  
Microstructural Evolution ◽  
High Stability ◽  
Isothermal Holding ◽  
Holding Time ◽  
Technological Parameters ◽  
Partial Remelting ◽  
Initial Stage ◽  
Semi Solid

The microstructural evolution of SiCp/AZ61 composites during partial remelting was investigated. The results indicated that the suitable technological parameters of SiCp/AZ61 composites were the reheating temperature of 595°C ~ 600°C and isothermal holding time of 30min ~ 60min. The separation of microstructure of AZ61 matrix was faster than that of SiCp/AZ61 composites during the initial stage. In the meantime, SiCp/AZ61composites hold high stability during remelting process and a fine semi-solid thixoforming microstructure can be obtained with increases in temperature and holding time. In addition, the samples of SiCp/AZ61composites were susceptible to serious deformation and running out above 610°C.

Development of Thixoextrusion Process for 7000 Series Al Wrought Alloys

2006 ◽  
Vol 116-117 ◽  
pp. 771-774 ◽  
Author(s):  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Jin Kyu Lee ◽  
Dong In Jang ◽  
Shae K. Kim
Keyword(s):  
Liquid Fraction ◽  
Isothermal Holding ◽  
Semisolid State ◽  
Grain Sizes ◽  
Partial Remelting ◽  
Different Content ◽  
Hardness Values ◽  
Holding Temperature

Thixoextrusion for 7003 and 7075 Al wrought alloys with different content of Cu was carried out with respect to isothermal holding temperature in the partially remelted semisolid state. Especially, despite higher extrudability index of 7075 Al wrought alloy compared with the extrudability index of 7003 Al wrought alloy, the maximum extrusion pressures of 7075 Al wrought alloy were about the same as the maximum extrusion pressures of 7003 Al wrought alloy at temperature with the liquid fraction 10% (7003-624, 7075-609). The hardness values of thixoextruded specimens were higher than that of as-quenched specimens only after partial remelting. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures. The average grain sizes of thixoextruded specimens were smaller than average grain sizes of homogenized specimens.

Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method

2016 ◽  
Vol 256 ◽  
pp. 294-300 ◽  
Author(s):  
Jin Long Fu ◽  
Yu Wei Wang ◽  
Kai Kun Wang ◽  
Xiao Wei Li
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Ostwald Ripening ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Semi Solid ◽  
Equiaxed Grains ◽  
Kinetics Of

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

scholarly journals Characterization and Alumina Leachability of 12CaO·7Al2O3with Different Holding Times

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Hui-lan Sun ◽  
Bo Wang ◽  
Jian-xin Zhang ◽  
Shu-feng Zong
Keyword(s):  
Grain Size ◽  
Surface Morphology ◽  
Lattice Constant ◽  
Preferred Orientation ◽  
Holding Time ◽  
Synthesis Time ◽  
Rate Of Increase ◽  
Average Grain Size ◽  
Long Time ◽  
Scherrer Formula

The effect of synthesis time on phase compositions, lattice constant, average grain size, preferred orientation, and surface morphology of 12CaO·7Al2O3synthesized at 1500°C was analyzed by XRD and SEM. The results indicate that the main phase of samples synthesized is 12CaO·7Al2O3when holding time is over 30 min. The lattice constant increases and the preferred orientation decreases as synthesis time prolongs. The average grain size of samples is about 59 nm calculated by Scherrer formula, and it does not change with synthesis time. The synthesis time affects the micromorphology of samples greatly. There are more and bigger holes in samples synthesized for long time. The aspects mentioned above cause the alumina leaching ratio of 12CaO·7Al2O3to increase with the prolonging of synthesis time, but the rate of increase drops.

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.

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