The Effect of Fluid Convection on Microstructures of Directionally Solidified Castings

2006 ◽  
Vol 508 ◽  
pp. 473-478 ◽  
Author(s):  
Tien Shou Lei ◽  
Wen Shiung Chang ◽  
Shyen Yang Dong
Keyword(s):  
Temperature Distribution ◽  
Directional Solidification ◽  
Ductile Iron ◽  
Lower Degree ◽  
Directionally Solidified ◽  
Matrix Microstructure ◽  
The Matrix ◽  
Fluid Convection ◽  
Cylindrical Casting ◽  
Set Up

Fluid convection during solidification of castings will influence the final structures of the castings. A vertical cylindrical casting set-up has been designed to provide two zones of solidification simultaneously with two moving fronts directionally upward and directionally downward, respectively. This two zone directional solidification casting was composed of a cylindrical Furan sand mold with a water chilled center hole block at the center of the casting. Experimentally it was observed that the cooling rates at different locations of the downward zone were much more even than those of the upward one and this is considered to be the result of a more even temperature distribution along the downward front moving zone due to stronger fluid convection. Fluid convection tends to mix up the liquid and results in a more even temperature distribution and a lower degree of segregation of the element molybdenum which has a strong tendency to segregate to the carbide in ductile iron. The characteristics of the matrix microstructure and the growing direction of carbide of this directionally solidified ductile iron has been investigated with SEM and EBSD techniques.

Study of Solid/Liquid Interface of Ti46Al0.5W0.5Si Ingot Directionally Solidified by a Near-Rectangular Cold Crucible

2012 ◽  
Vol 472-475 ◽  
pp. 767-770
Author(s):  
Rui Run Chen ◽  
Jie Ren Yang ◽  
Hong Sheng Ding ◽  
Jing Jie Guo ◽  
Yan Qing Su ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Directional Solidification ◽  
Process Parameters ◽  
Electromagnetic Stirring ◽  
Cold Crucible ◽  
Interface Morphology ◽  
Directionally Solidified ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Future Work

In this study, Ti46Al0.5W0.5Si ingots were directionally solidified by a near-rectangular cold crucible under different process parameters. These process parameters include the electromagnetic stirring, the crucible configuration and the molten drop, all of them have important effect on the S/L interface. The effects of the parameters on the solid/liquid (S/L) interface morphology were investigated, and the mechanisms of the parameters influencing the S/L interface were discussed and revealed. Results showed that the typical S/L interface of the ingots was presented as a curved ‘W-type’ shape. The uneven temperature distribution in the front of the solidified interface is the main reason for a curved S/L interface. Further, the requirements for obtaining a planar S/L interface in the process of cold crucible directional solidification were given, which provided a guide for the future work.

Influence of growth parameters on the microstructure of directionally solidified Bi2Sr2CaCu2Oy

1990 ◽  
Vol 5 (9) ◽  
pp. 1834-1849 ◽  
Author(s):  
M. J. Cima ◽  
X. P. Jiang ◽  
H. M. Chow ◽  
J. S. Haggerty ◽  
M. C. Flemings ◽  
...  
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Growth Rates ◽  
Growth Parameters ◽  
Directionally Solidified ◽  
Primary Solidification Phase ◽  
Float Zone ◽  
The Matrix ◽  
Laser Heated ◽  
Planar Growth

Laser-heated float zone growth was used to study the directional solidification behavior of Bi–Sr–Ca–Cu–O superconductors. The phases that solidify from the melt, their morphology, and their composition are altered by growth rate. Highly textured microstructures are achieved by directional solidification at all growth rates. The superconducting phase is found always to have the composition Bi2.5Sr2CaCu2.2Oy when grown from boules with composition 2:2:1:2 (BiO1.5:SrO:CaO:CuO). Planar growth fronts of Bi2.5Sr2CaCu2.2Oy are observed when the temperature gradient divided by the growth rate (G/R) is larger than 3 ⊠ 1011 K-s/m2 in 2.75 atm oxygen. Thus, the 2212 compound was observed to solidify directly from the melt at the slowest growth rates used in this study. Measurement of the steady-state liquid zone composition indicates that it becomes bismuth-rich as the growth rate decreases. Dendrites of the primary solidification phase, (Sr1−xCax)14Cu24Oy, form in a matrix of Bi2.5Sr2CaCu2.2Oy when G/R is somewhat less than 3 ⊠ 1011 K-s/m2. Observed microstructures are consistent with a peritectic relationship among Bi2.5Sr2CaCu2.2Oy, (Sr1−xCax)14Cu24Oy (x = 0.4), and a liquid rich in bismuth at elevated oxygen pressure. At lower values of G/R, Sr3Ca2Cu5Oy is the primary solidification phase and negligible Bi2.5Sr2CaCu2.2Oy forms in the matrix.

Microstructure Evolution and Macro Segregation of Directionally Solidified Hypoeutectic and Hypereutectic Lead-Tin Alloys

2017 ◽  
Vol 895 ◽  
pp. 3-7
Author(s):  
K.V. Sreenivas Rao ◽  
N. Akhil
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Microstructure Evolution ◽  
Solidification Rate ◽  
Unidirectional Solidification ◽  
Directionally Solidified ◽  
Tin Alloys ◽  
Alloy Increase ◽  
Set Up ◽  
Tin Content

Unidirectional solidification is preferred to multidirectional solidification for growing crystals in a particular direction. An experimental set-up consisting of Bridgman type of upward directional solidification was employed for the present investigation. The main aim of the present investigation was to assess the effect of unidirectional upward solidification on the segregation of off-eutectic Pb-Sn alloys at different translational speeds of the experimental set-up. Solidification experiments were conducted on hypoeutectic and hypereutectic Lead-Tin alloys. Different combinations of growth rate V and composition Co. were used to investigate their effect on longitudinal macro segregation. Macro segregation along the length of the samples was observed in hypoeutectic Pb-Sn alloys whereas no such macro segregation was observed in hypereutectic alloys. The intensity of longitudinal macro segregation was found to increase with the increase in initial tin content of the alloy, increase in distance from the chill end and decrease in the solidification rate.

The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

1992 ◽  
Vol 50 (2) ◽  
pp. 1696-1697
Author(s):  
H.J. Zuo ◽  
M.W. Price ◽  
R.D. Griffin ◽  
R.A. Andrews ◽  
G.M. Janowski
Keyword(s):  
Directional Solidification ◽  
Space Shuttle ◽  
Solidification Process ◽  
Space Experiment ◽  
Infrared Detection ◽  
Directionally Solidified ◽  
Crystallographic Defects ◽  
Semiconducting Alloys ◽  
Uniform Composition ◽  
Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

Effect of matrix microstructure on the matrix/M2B wear interaction and its quantitative characterization in an Fe-2wt%B alloy

Wear ◽  
2021 ◽  
Vol 472-473 ◽  
pp. 203608
Author(s):  
Yanliang Yi ◽  
Qiang Li ◽  
Shaolei Long ◽  
Zhen Lv ◽  
Shuangjian Li ◽  
...  
Keyword(s):  
Quantitative Characterization ◽  
Matrix Microstructure ◽  
The Matrix

Temperature Distribution of Hot Air Flow in Heating Zone for Drying Application

2014 ◽  
Vol 627 ◽  
pp. 153-157
Author(s):  
Nawadee Srisiriwat ◽  
Chananchai Wutthithanyawat
Keyword(s):  
Temperature Distribution ◽  
Air Temperature ◽  
Power Supply ◽  
Air Flow ◽  
Heating Zone ◽  
Velocity Control ◽  
Rectangular Duct ◽  
Air Velocity ◽  
Hot Air ◽  
Set Up

The temperature distribution of hot air flow in heating zone of a rectangular duct has been investigated for drying application. The experimental set-up consists of a heater and a fan to generate the hot air flow in the range of temperature from 40 to 100°C and the range of air velocity between 1.20 and 1.57 m/s. An increase of the heater power supply increases the hot air temperature in the heating zone while an increase of air velocity forced by fan decreases the initial temperature at the same power supply provided to generate the hot air flow. The temperature distribution shows that the hot air temperature after transferring through air duct decreases with an increase of the length of the rectangular duct. These results are very important for the air flow temperature and velocity control strategy to apply for heating zone design in the drying process.

Position Estimation of Single Camera Visual System Based on Total Least Squares Algorithm

2012 ◽  
Vol 239-240 ◽  
pp. 1352-1355
Author(s):  
Jing Zhou ◽  
Yin Han Gao ◽  
Chang Yin Liu ◽  
Ji Zhi Li
Keyword(s):  
Visual System ◽  
Least Squares ◽  
Total Least Squares ◽  
Position Estimation ◽  
Feature Points ◽  
Perspective Theory ◽  
Optical Feature ◽  
The Matrix ◽  
Least Squares Algorithm ◽  
Set Up

The position estimation of optical feature points of visual system is the focus factor of the precision of system. For this problem , to present the Total Least Squares Algorithm . Firstly , set up the measurement coordinate system and 3D model between optical feature points, image points and the position of camera according to the position relation ; Second , build the matrix equations between optical feature points and image points ; Then apply in the total least squares to have an optimization calculation ; Finally apply in the coordinate measuring machining to have a simulation comparison experiment , the results indicate that the standard tolerance of attitude coordinate calculated by total least squares is 0.043mm, it validates the effectiveness; Compare with the traditional method based on three points perspective theory, measure the standard gauge of 500mm; the standard tolerance of traditional measurement system is 0.0641mm, the standard tolerance of Total Least Squares Algorithm is 0.0593mm; The experiment proves the Total Least Squares Algorithm is effective and has high precision.

scholarly journals Research and Practice of individualized talent Training Mode for rail transit majors from the perspective of new engineering

2020 ◽  
Vol 218 ◽  
pp. 02003
Author(s):  
Zhao Wu ◽  
Hai Xiang Li ◽  
Jun Ying Qi
Keyword(s):  
Evaluation System ◽  
Teaching Practice ◽  
Implementation Process ◽  
Training Model ◽  
Urban Rail Transit ◽  
Rail Transit ◽  
Existing Problems ◽  
Training Mode ◽  
The Matrix ◽  
Set Up

In order to cultivate application-oriented talents of urban rail transit, individualized talent training mode is an important measure. In view of the existing problems in the training of rail transit professionals, the research group proposed the framework of individualized talent training under the background of new engineering, planned the matrix corresponding to graduation requirements and knowledge, ability and quality, and then set up the curriculum system and built the multi-evaluation system in the implementation process. The developed solution has been put into practice and will be tested in the future teaching practice activities in order to constantly improve the personalized talent training model.

AC Magnetic Measurements on Superconductors

2013 ◽  
pp. 208-222
Author(s):  
Philippe Laurent ◽  
Jean-François Fagnard ◽  
Philippe Vanderbemden
Keyword(s):  
Magnetic Properties ◽  
Temperature Distribution ◽  
Magnetic Measurements ◽  
Sampling Rate ◽  
Data Acquisition System ◽  
Magnetic Data ◽  
Magnetic Characterization ◽  
Set Up ◽  
Cryogenic Conditions

This work describes the design and realisation of an apparatus to measure simultaneously the AC magnetic properties and the temperature distribution on the top surface of bulk superconducting samples (up to 32 mm in diameter) in cryogenic conditions (temperature range 78-120 K). First the authors describe the experimental set-up used for simultaneous thermal and magnetic characterization of the sample. Next, the authors describe the practical considerations required for generating the large AC magnetic fields, possibly in the presence of DC fields. Then the authors present the data acquisition system allowing both temperature and magnetic data to be recorded at high a sampling rate.” The performances and limitations of the system are discussed.

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