Unidirectional solidification of Zn-rich Zn-Cu hypoperitectic alloy

2009 ◽  
Vol 24 (11) ◽  
pp. 3422-3431 ◽  
Author(s):  
Hasan Kaya ◽  
Sevda Engin ◽  
U. Böyük ◽  
Emin Çadırlı ◽  
Necmettin Maraşlı
Keyword(s):  
Growth Rate ◽  
Numerical Models ◽  
Linear Regression Analysis ◽  
Graphite Crucible ◽  
Processing Parameters ◽  
Unidirectional Solidification ◽  
Experimental Results ◽  
Constant Growth Rate ◽  
Microstructure Parameters ◽  
Tip Radius

Zn-0.7 wt.% Cu-hypoperitectic alloy was prepared in a graphite crucible under a vacuum atmosphere. Unidirectional solidification of the Zn-0.7 wt.% Cu-hypoperitectic alloy was carried out by using a Bridgman-type directional solidification apparatus under two different conditions: (i) with different temperature gradients (G = 3.85–9.95 K/mm) at a constant growth rate (41.63 μm/s) and (ii) with different growth rate ranges (G = 8.33–435.67 μm/s) at a constant temperature gradient (3.85 K/mm). The microstructures of the directionally solidified Zn-0.7 wt.% Cu-hypoperitectic samples were observed to be a cellular structure. From both transverse and longitudinal sections of the samples, cellular spacing (λ) and cell-tip radius (R) were measured. The effects of solidification-processing parameters (G and V) on the microstructure parameters (λ and R) were obtained by using a linear regression analysis. The present experimental results were also compared with the current theoretical and numerical models and similar previous experimental results.

Relationship between Growth Rates and Dendritic Microstructure Parameters in Al-5wt. Zn Binary Alloy

2013 ◽  
Vol 765 ◽  
pp. 215-219 ◽  
Author(s):  
Emine Acer ◽  
Harun Erol ◽  
Mehmet Gündüz
Keyword(s):  
Growth Rates ◽  
Numerical Models ◽  
Primary Dendrite ◽  
Linear Regression Analysis ◽  
Experimental Results ◽  
Directionally Solidified ◽  
Dendritic Microstructure ◽  
Dendrite Arm Spacing ◽  
Primary Dendrite Arm Spacing ◽  
Microstructure Parameters

Al-5 wt.% Zn samples were prepared using high purity (99.99%) metals in graphite crucibles. The samples were directionally solidified upward with a constant temperature gradient (G= 5.5 Kmm-1) and different growth rates,V, (8.25-165 μm/s) in a Bridgman type directional solidification apparatus. The dendritic spacings (λ1: Primary dendrite arm spacing, and λ2: Secondary dendrite arm spacing) were measured from the longitudinal sections of the samples and λ1was also measured from the transverse sections. The measured spacings were expressed as functions of the growth rates by using a linear regression analysis. The effect ofVon λ1and λ2were investigated. The experimental results were compared with the results of the current theoretical and numerical models and similar previous experimental results.

INFLUENCE OF THE SOLIDIFICATION PARAMETERS ON DENDRITIC MICROSTRUCTURES IN UNSTEADY-STATE DIRECTIONALLY SOLIDIFIED OF LEAD–ANTIMONY ALLOY

2010 ◽  
Vol 17 (05n06) ◽  
pp. 477-486 ◽  
Author(s):  
M. ŞAHIN ◽  
E. ÇADIRLI ◽  
H. KAYA
Keyword(s):  
Growth Rate ◽  
Primary Dendrite ◽  
Linear Regression Analysis ◽  
Theoretical Models ◽  
Directionally Solidified ◽  
Constant Growth Rate ◽  
Dendrite Arm Spacing ◽  
Primary Dendrite Arm Spacing ◽  
Microstructure Parameters ◽  
Solidification Parameters

Pb-9.3wt.%Sb alloy was directionally solidified upwards under argon atmosphere under the two conditions; with different temperature gradients, (G = 0.93–3.67 K/mm) at a constant growth rate (V = 17.50 μm/s) and with different growth rates (V = 8.30–497.00 μm/s) at a constant (G = 3.67 K/mm) in a Bridgman furnace. The dependence of characteristic microstructure parameters such as primary dendrite arm spacing (λ1), secondary dendrite arm spacing (λ2) and dendrite tip radius (R) on the growth rate (V) and the temperature gradient (G) were determined by using a linear regression analysis. A detailed analysis of microstructure were also made and compared with the theoretical models and similar experimental works on dendritic solidification in the literature.

SOLIDIFICATION CHARACTERISTICS AND MICROSTRUCTURAL EVOLUTION OF Zn-1.26wt.% Al ALLOY

2011 ◽  
Vol 18 (06) ◽  
pp. 281-288 ◽  
Author(s):  
MEVLÜT ŞAHİN ◽  
EMİN ÇADIRLI
Keyword(s):  
Primary Dendrite ◽  
Linear Regression Analysis ◽  
Al Alloy ◽  
Constant Growth Rate ◽  
Dendrite Arm Spacing ◽  
Wide Range ◽  
Primary Dendrite Arm Spacing ◽  
Microstructure Parameters ◽  
Solidification Furnace ◽  
Tip Radius

Zn–1.26 wt.% Al alloy was directionally solidified upward with a constant growth rate (V = 16.6 μm/s) in a wide range of temperature gradients (G = 1.94–5.15 K/mm) and with a constant temperature gradient (G = 5.15 K/mm) in a wide range of growth rates (V = 8.3–500 μm/s) with a Bridgman-type directional solidification furnace. Microstructure parameters, the primary dendrite arm spacing (λ1), secondary dendrite arm spacing (λ2) and dendrite tip radius (R), were measured and expressed as functions of G and V by using a linear regression analysis method. It was found that the values of λ1, λ2 and R decrease with increasing values of V and G. The experimental results were compared with the main predictive theoretical and experimental works for dendritic spacings.

Diffusion solidification model on Y-system superconductors

1992 ◽  
Vol 7 (7) ◽  
pp. 1621-1628 ◽  
Author(s):  
Teruo Izumi ◽  
Yuichi Nakamura ◽  
Yuh Shiohara
Keyword(s):  
Growth Rate ◽  
Growth Mechanism ◽  
Peritectic Reaction ◽  
Unidirectional Solidification ◽  
Experimental Results ◽  
Solidification Model ◽  
Zone Melt ◽  
Good Agreement

The unidirectional solidification of the zone melt method was performed in order to clarify the growth mechanism on Y-system superconductors. A sharp faceted interface of YBa2Cu3Oy (123) crystals was obtained in the sample grown at the low growth rate of 1 mm/h. The volume of the 211 phase changed drastically from liquid to 123 crystal. These results lead to the idea that the necessary solute for peritectic reaction is provided through a liquid. Based on this idea, we developed a simple solidification model that is in good agreement with the experimental results.

DENDRITIC GROWTH OF THE BINARY SUCCINONITRILE-CAMPHOR SYSTEM

2007 ◽  
Vol 14 (06) ◽  
pp. 1169-1179 ◽  
Author(s):  
E. ÇADIRLI ◽  
H. KAYA
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Primary Dendrite ◽  
Alloy System ◽  
Theoretical Models ◽  
Experimental Results ◽  
Constant Growth Rate ◽  
Microstructural Parameters ◽  
Zone Depth ◽  
The Stability

Succinonitrile (SCN)–2 wt% Camphor (CAMP) alloy was unidirectionally solidified with a constant temperature gradient (G = 3.01 K/mm ) at different growth rates (V = 6.5–113 μ m/s ) and with a constant growth rate (V = 6.5 μ m/s ) at different temperature gradients (G = 1.93 - 3.01 K/mm ). Microstructural parameters (primary dendrite arm spacings, λ1, secondary dendrite arm spacings, λ2, dendrite tip radius, R, and mushy zone depth, d) were measured as a function of growth rate and temperature gradient. The experimental results have been compared with theoretical models and previous experimental works. The stability constant (σ) for this alloy system was calculated and compared with similar experimental results.

Comparison of Nodular Efficiencies Between Partridge Pea and Soybean Using Acetylene Reduction

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 449f-450
Author(s):  
Lisa M. Barry ◽  
Michael N. Dana
Keyword(s):  
Growth Rate ◽  
Plant Size ◽  
Silica Sand ◽  
Soybean Plant ◽  
Fibrous Root ◽  
Constant Growth Rate ◽  
Soil Microbial ◽  
Soybean Plants ◽  
Nurse Crops ◽  
Partridge Pea

Legumes are grown as nurse crops in agriculture because they increase soil microbial life and productivity. Native legumes have potential in ecological restoration to mimic the benefits found in agriculture plus they enhance the restored ecosystem. This study was initiated to compare the growth rates, nodulation characteristics, and nitrogen fixation rates of a native versus a non-native legume. The two legumes were partridge pea (Cassia fasciculata); a native, wild, annual legume and soybean (Glycine max `Century Yellow); a domesticated, agricultural, annual legume native to Asia. Plants were grown for 11 weeks in pots containing silica sand and received a nitrogen-free Hoagland's nutrient solution. Beginning at week 12, plants were harvested weekly for four consecutive weeks. Nodulated root systems were exposed to acetylene gas and the resulting ethylene amounts were measured. The two legumes exhibited significant differences in nodule size and shape and plant growth rate. In soybean, nodules were large, spherical, and clustered around the taproot while in partridge pea, nodules were small, irregularly shaped, and spread throughout the fibrous root system. Soybean plants had a significantly faster growth rate at the onset of the experiment but partridge pea maintained a constant growth rate and eventually exceeded soybean plant size. In spite of these observed differences, partridge pea and soybean plants were equally efficient at reducing acetylene to ethylene. These results indicate partridge pea has the potential to produce as much nitrogen in the field as soybean. Native legumes such as partridge pea deserve further research to explore their use as nurse crops in agricultural or restoration regimes.

scholarly journals Proximate Factors Determining Age and Mass at Fledging in Rhinoceros Auklets (Cerorhinca Monocerata): Intra- and Interyear Variations

The Auk ◽  
2004 ◽  
Vol 121 (2) ◽  
pp. 452-462 ◽  
Author(s):  
Tomohiro Deguchi ◽  
Akinori Takahashi ◽  
Yutaka Watanuki
Keyword(s):  
Growth Rate ◽  
Wing Length ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Major Effect ◽  
Timing Of Breeding ◽  
Hatching Date ◽  
Cerorhinca Monocerata ◽  
Parental Provisioning ◽  
Underlying Mechanisms

Abstract In alcids, growth rate and hatching date of chicks appear to affect fledging age and mass. Underlying mechanisms are hypothesized to be (1) critical wing length at fledging for postfledging survival, (2) synchronization of fledging to dilute predation risk, and (3) variable parental provisioning according to timing of breeding. To elucidate the effects of growth rate and hatching date on fledging age and mass, and to test those mechanistic hypotheses, we measured chick growth and fledging periods in Rhinoceros Auklets (Cerorhinca monocerata) at Teuri Island from 1995 to 2000. The multiple-linear regression analysis showed that intrayear variations of fledging age and mass were explained by growth rate or hatching date in five out of six years. Faster-growing chicks fledged younger and heavier, and earlier-hatched chicks fledged older and heavier. Consequently, no apparent correlation between fledging age and mass was observed in five out of six years. Analysis of interyear variation showed a negative correlation between fledging age and mass, which indicates that growth rates rather than hatching dates had a major effect. Wing length at fledging was independent of growth in mass. More than 80% of chicks fledged when they attained a narrow range of wing length (130–150 mm), presumably because they remained in their nests until they attained the critical wing length. In five out of six years, the chicks did not synchronize timing of fledging relative to timing of hatching. Later-hatched chicks attained lighter peak masses and at younger ages, which may indicate that their parents decreased provisioning rates when the chicks were still young. We suggest that (1) critical wing length at fledging and (2) variable parental provisioning according to timing of breeding could be underlying mechanisms determining these relationships between fledging age and mass.

scholarly journals Numerical and experimental evaluation of masonry prisms by finite element method

2017 ◽  
Vol 10 (2) ◽  
pp. 477-508 ◽  
Author(s):  
C. F.R. SANTOS ◽  
R. C. S. S. ALVARENGA ◽  
J. C. L. RIBEIRO ◽  
L. O CASTRO ◽  
R. M. SILVA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
High Strength Concrete ◽  
Numerical Models ◽  
High Strength ◽  
Experimental Tests ◽  
Experimental Results ◽  
Concrete Blocks ◽  
Micro Modeling ◽  
Modeling Strategy

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

Study of the Size Effects and Friction Conditions in Microextrusion—Part II: Size Effect in Dynamic Friction for Brass-Steel Pairs

2007 ◽  
Vol 129 (4) ◽  
pp. 677-689 ◽  
Author(s):  
Lapo F. Mori ◽  
Neil Krishnan ◽  
Jian Cao ◽  
Horacio D. Espinosa
Keyword(s):  
Grain Size ◽  
Friction Coefficient ◽  
Size Effect ◽  
Contact Pressure ◽  
Size Effects ◽  
Numerical Models ◽  
Kolsky Bar ◽  
Experimental Results ◽  
Material Response ◽  
Dynamic Coefficients

In this paper, the results of experiments conducted to investigate the friction coefficient existing at a brass-steel interface are presented. The research discussed here is the second of a two-part study on the size effects in friction conditions that exist during microextrusion. In the regime of dimensions of the order of a few hundred microns, these size effects tend to play a significant role in affecting the characteristics of microforming processes. Experimental results presented in the previous companion paper have already shown that the friction conditions obtained from comparisons of experimental results and numerical models show a size effect related to the overall dimensions of the extruded part, assuming material response is homogeneous. Another interesting observation was made when extrusion experiments were performed to produce submillimeter sized pins. It was noted that pins fabricated from large grain-size material (211μm) showed a tendency to curve, whereas those fabricated from billets having a small grain size (32μm), did not show this tendency. In order to further investigate these phenomena, it was necessary to segregate the individual influences of material response and interfacial behavior on the microextrusion process, and therefore, a series of frictional experiments was conducted using a stored-energy Kolsky bar. The advantage of the Kolsky bar method is that it provides a direct measurement of the existing interfacial conditions and does not depend on material deformation behavior like other methods to measure friction. The method also provides both static and dynamic coefficients of friction, and these values could prove relevant for microextrusion tests performed at high strain rates. Tests were conducted using brass samples of a small grain size (32μm) and a large grain size (211μm) at low contact pressure (22MPa) and high contact pressure (250MPa) to see whether there was any change in the friction conditions due to these parameters. Another parameter that was varied was the area of contact. Static and dynamic coefficients of friction are reported for all the cases. The main conclusion of these experiments was that the friction coefficient did not show any significant dependence on the material grain size, interface pressure, or area of contact.

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