Thermal Parameters, Tertiary Dendritic Growth and Microhardness of Directionally Solidified Al-3wt%Cu Alloy

2016 ◽  
Vol 869 ◽  
pp. 452-457 ◽  
Author(s):  
André Santos Barros ◽  
Maria Adrina Paixão de Souza da Silva ◽  
Otávio Fernandes Lima da Rocha ◽  
Antonio Luciano Seabra Moreira
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Cooling Rate ◽  
Dendritic Growth ◽  
Solidification Process ◽  
Flow Conditions ◽  
Directionally Solidified ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Transient Heat Flow

The main purpose of this paper is to evaluate both tertiary dendritic arm growth and microhardness of Al-3wt%Cu alloy during horizontal directional solidification under transient heat flow conditions. Experimental thermal profiles recorded during solidification process allowed to determine growth rate and cooling rate values which are associated with both tertiary dendritic arm spacings and microhardness. The results show that initial tertiary branches growth only occurs when a cooling rate value of 1.14 K/s is reached. Variation of tertiary spacings is expressed as-1.1 and-0.55 power law functions of growth rate and cooling rate, respectively. A comparative analysis with other studies published in the literature that analyze tertiary dendritic growth of Al-Cu alloys considering transient directional solidification is carried out. Dependence of microhardness on dendritic arrangement is evaluated by experimental laws of power and Hall-Petch types with a view to permitting the applicability of the resulting expressions.

The Growth of Secondary Dendritic Arms in Directionally Solidified Al-Si-Cu Alloys: A Comparative Study with Binary Al-Si Alloys

2015 ◽  
Vol 719-720 ◽  
pp. 102-105 ◽  
Author(s):  
Laércio G. Gomes ◽  
Daniel J. Moutinho ◽  
Ivaldo L. Ferreira ◽  
Otávio L. Rocha ◽  
Amauri Garcia
Keyword(s):  
Growth Rate ◽  
Directional Solidification ◽  
Dendritic Growth ◽  
Ternary Alloys ◽  
Unsteady State ◽  
Directionally Solidified ◽  
Cu Alloys ◽  
Theoretical Predictions ◽  
Growth Laws ◽  
Experimental Scatter

Experiments of vertical unsteady-state directional solidification were carried out in order to permit the influence of copper alloying to Al-Si alloys on the scale of secondary dendritic arm (λ2) to be investigated. The microstructures of Al-nSi-3wt%Cu alloys, with “n” equal to 5.5wt%Si and 9.0wt%Si, were characterized and correlated with solidification thermal parameters: the growth rate (VL), the tip cooling rate (Ṫ) and the local solidification time (tSL). A comparative analysis between the present results and those from the literature related to the secondary dendrite growth during directional solidification of Al-nSi alloys is also conducted. It is shown that the addition of Cu to both Al-nSi alloys decreases λ2, and experimental growth laws relating λ2 to VL and ṪL are proposed for the ternary alloys examined. The experimental scatter of λ2 is also compared with the only theoretical dendritic growth model from the literature for multicomponent alloys, and it is shown that the theoretical predictions overestimate the present experimental results.

Microstructural Evolution during the Directional Transient Solidification of a Hypomonotectic Al-0.9wt%Pb Alloy

2012 ◽  
Vol 730-732 ◽  
pp. 829-834
Author(s):  
Adrina P. Silva ◽  
Pedro R. Goulart ◽  
José Eduardo Spinelli ◽  
Amauri Garcia
Keyword(s):  
Growth Rate ◽  
Heat Flow ◽  
Thermal Parameters ◽  
Cooling Curves ◽  
Flow Conditions ◽  
Directionally Solidified ◽  
Microstructural Transition ◽  
Transient Heat Flow ◽  
Growth Laws ◽  
Casting Length

In the present study a hypomonotectic Al-0.9wt%Pb alloy was directionally solidified under transient heat flow conditions and the microstructure evolution was analyzed. The solidification thermal parameters such as the growth rate, the cooling rate and the temperature gradient were experimentally determined by cooling curves recorded by thermocouples positioned along the casting length. The monotectic structure was characterized by metallography and a microstructural transition was observed. From the casting cooled surface up to a certain position in the casting the microstructure was characterized by well-distributed Pb-rich droplets in the aluminum-rich matrix, followed by a mixture of fibers and strings of pearls from this point to the top of the casting. The interphase spacing (λ) and the diameter of Pb-rich particles were also measured along the casting length and experimental growth laws relating these microstructural features to the experimental thermal parameters are proposed.

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.

Morphological Characteristics of W-Nanowires after Selective Etching

2014 ◽  
Vol 1004-1005 ◽  
pp. 24-27
Author(s):  
Wen Jia Wang ◽  
Zhi Long Zhao ◽  
Ming Tang ◽  
Jian Jun Gao
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Directional Solidification ◽  
Morphological Characteristics ◽  
Selective Dissolution ◽  
Stability Diagram ◽  
Selective Etching ◽  
Directionally Solidified ◽  
Solidification Furnace ◽  
Nial Matrix

An eutectic NiAl–1.5 at.% W alloy prepared by using directionally solidified (DS)was employed as a source for producing W-nanowires. Several growth rate of 8,15,25/s was respectively used at a temperature gradient of ~240 K/cm in a Bridgman-type directional solidification furnace. A combined stability diagram was applied to predict proper conditions for the selective dissolution of NiAl matrix to get W-wires. Etching in a mixture of HCl:H2O2released parallel aligned W-nanowires with a wire diameter of ~500 nm. Different morphologies, such as nanobelts, lotus-shaped, conical of W-nanowires are obtained at the different conditions.

Macrosegregation and Porosity during Directional Solidification of a Ternary Al-9wt%Si-3wt%Cu Alloy

2011 ◽  
Vol 312-315 ◽  
pp. 405-410
Author(s):  
L.G. Gomes ◽  
P. D. Jácome ◽  
Ileao L. Ferreira ◽  
D.J. Moutinho ◽  
O.L. Rocha ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Input Parameter ◽  
Typical Result ◽  
Directionally Solidified ◽  
Local Composition ◽  
X Ray ◽  
Cu Alloy ◽  
Macrosegregation Pattern ◽  
Experimental Scatter ◽  
Casting Length

Macrosegregation and porosity formation have been investigated by both a numerical model and by transient directional solidification experiments. The macrosegregation pattern, the theoretical and apparent densities are presented as a function of the casting length. X-ray fluorescence spectrometry was used to determine the macrosegregation profiles. The measurement of microporosity was performed using pyknometry analysis. The local composition along an Al-9wt%Si-3wt%Cu casting length was used as an input parameter for simulations of microporosity evolution. The results have demonstrated that the presence of Si in the alloy composition has inhibited the inverse copper segregation, which is a typical result of directionally solidified Al-Cu castings. The numerically simulated trend is in good conformity with the experimental scatter.

Analysis of the Microstructural Evolution during the Transient Upward, Downward and Horizontal Directional Solidification of the Al-1.2wt%Pb Monotectic Alloy

2016 ◽  
Vol 869 ◽  
pp. 429-434 ◽  
Author(s):  
Camila Yuri Negrão Konno ◽  
Angela J. Vasconcelos ◽  
André Santos Barros ◽  
Adrina P. Silva ◽  
Otávio Fernandes Lima da Rocha ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Microstructural Evolution ◽  
Convective Flow ◽  
Tribological Behavior ◽  
Eutectic Growth ◽  
Monotectic Reaction ◽  
Flow Conditions ◽  
Power Functions ◽  
Monotectic Alloy ◽  
Transient Heat Flow

Monotectic alloys are of great industrial importance because of their favorable tribological behavior. Many studies in order to better understand the morphologies obtained by monotectic reaction have been developed. To better understand the morphologies obtained by monotectic Al-1.2wt%Pb alloy reaction, especially in relation to induced convective flow, this paper aims to compare the microstructural evolution of the alloy obteind by directional solidification in transient heat-flow conditions in upward, downwand and horizontal solidification devices. It was observed a morphology transition from particles to fibers on upward and downward cases and a morphology of only particles on the horizontal case. The classical relationship used for eutectic growth, λ2v = C, which was considered applicable to monotectic reactions, didn’t seemed to be valid in the interphase spacing evolution for the downward device, however power functions (λ = C.va) were found in all cases.

scholarly journals Mesoscopic Simulation of Dendritic Growth Observed in X-ray Video Microscopy During Directional Solidification of Al–Cu Alloys

2010 ◽  
Vol 50 (12) ◽  
pp. 1886-1894 ◽  
Author(s):  
Pierre Delaleau ◽  
Christoph Beckermann ◽  
Ragnvald H. Mathiesen ◽  
Lars Arnberg
Keyword(s):  
Directional Solidification ◽  
Dendritic Growth ◽  
Video Microscopy ◽  
Mesoscopic Simulation ◽  
X Ray ◽  
Cu Alloys

INFLUENCE OF GROWTH RATE ON MICROSTRUCTURE AND MICROINDENTATION HARDNESS OF DIRECTIONALLY SOLIDIFIED TIN–CADMIUM EUTECTIC ALLOY

2009 ◽  
Vol 16 (02) ◽  
pp. 191-201 ◽  
Author(s):  
E. ÇADIRLI ◽  
H. KAYA ◽  
M. GÜNDÜZ
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Directional Solidification ◽  
Constant Temperature ◽  
Eutectic Alloy ◽  
Directionally Solidified ◽  
Constant Temperature Gradient ◽  
Microindentation Hardness ◽  
Solidification Furnace ◽  
Eutectic Melt

Sn – Cd eutectic melt was first obtained in a hot filling furnace and then directionally solidified upward with different growth rate ranges (8.1–165 μm/s) at a constant temperature gradient G (4.35 K/mm) in the Bridgman-type directional solidification furnace. The lamellar spacings (λ) were measured from both transverse and longitudinal sections of the samples. The influence of the growth rate (V) on lamellar spacings (λ) and undercoolings (Δ T) was analyzed. λ2V, ΔTλ and ΔTV-0.5 values were determined by using λ,ΔT and V values. Microindentation hardness (HV) was measured from both transverse and longitudinal sections of the specimens. HV values increase with the increasing values of V but decrease with increasing λ values. λ-V, λ - ΔT and λ2V results have been compared with the Jackson–Hunt eutectic model and similar experimental results, HV - V and HV - λ results were also compared with the previous work.

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