scholarly journals Investigation of Microstructure Evolution and Phase Selection of Peritectic Cuce Alloy During High-Temperature Gradient Directional Solidification

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 911
Author(s):  
Yiku Xu ◽  
Zhaohao Huang ◽  
Yongnan Chen ◽  
Junxia Xiao ◽  
Jianmin Hao ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Primary Dendrite ◽  
Primary Phase ◽  
Withdrawal Rate ◽  
Compressive Property ◽  
Directionally Solidified ◽  
Phase Selection ◽  
Coupled Growth ◽  
Selection Of

In this work, a CuCe alloy was prepared using a directional solidification method at a series of withdrawal rates of 100, 25, 10, 8, and 5 μm/s. We found that the primary phase microstructure transforms from cellular crystals to cellular peritectic coupled growth and eventually, changes into dendrites as the withdrawal rate increases. The phase constituents in the directionally solidified samples were confirmed to be Cu2Ce, CuCe, and CuCe + Ce eutectics. The primary dendrite spacing was significantly refined with an increasing withdrawal rate, resulting in higher compressive strength and strain. Moreover, the cellular peritectic coupled growth at 10 μm/s further strengthened the alloy, with its compressive property reaching the maximum value of 266 MPa. Directional solidification was proven to be an impactful method to enhance the mechanical properties and produce well-aligned in situ composites in peritectic systems.

Microstructure and microtexture of a Nb-16%Si (DS) Alloy

1995 ◽  
Vol 53 ◽  
pp. 122-123
Author(s):  
J. A. Sutliff ◽  
B. P. Bewlay
Keyword(s):  
High Temperature ◽  
Directional Solidification ◽  
Room Temperature ◽  
Microstructural Characterization ◽  
Crystallographic Analysis ◽  
Directionally Solidified ◽  
Heat Treated ◽  
Other Orientation

In-situ composite Nb-Si alloys have been studied by several investigators as potential high temperature structural materials. The two major processing routes used to fabricate these composites are directional solidification and extrusion of arc-cast solidified ingots. In both cases a stable microstructure of primary Nb dendrites in a eutectoid of Nb and Nb5Si3 phases is developed after heat treatment. The Nb5Si3 phase is stable at room temperature and forms as a decomposition product of the high temperature Nb3Si phase. The anisotropic microstructures developed by both directional solidification and extrusion require evaluation of the texture to fully interpret the fracture and other orientation dependent mechanical behavior of these composites.In this paper we report on the microstructural characterization of a directionally solidified (DS) and heat treated Nb-16 at.%Si alloy. The microtexture of each of the phases (Nb, Nb5Si3) was determined using the Electron BackScattering Pattern (EBSP) technique for electron diffraction in the scanning electron microscope. A system employing automatic diffraction pattern recognition, crystallographic analysis, and sample or beam scanning was used to acquire the microtexture data.

Effects of the Interface Curvature and Dendrite Orientation in Directional Solidification of Bulk Transparent Alloys

2006 ◽  
Vol 508 ◽  
pp. 337-342 ◽  
Author(s):  
Cedric Weiss ◽  
Nathalie Bergeon ◽  
Nathalie Mangelinck-Noël ◽  
Bernard Billia
Keyword(s):  
Directional Solidification ◽  
Optical Methods ◽  
Fundamental Physics ◽  
Materials Engineering ◽  
Interface Curvature ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Selection Of

The properties of structural materials are to a large extent determined by the solid microstructure so that the understanding of the fundamental physics of microstructure formation is critical in the field of materials engineering. A directional solidification facility dedicated to the characterization of solid-liquid interface morphology by means of optical methods has been developed by CNES in the frame of the DECLIC project. This device enables in situ and real time studies on bulk transparent materials. The aim of the project is to perform experiments in microgravity to eliminate the complex couplings between solidification and convection and to get reliable benchmark data to validate and calibrate theoretical modeling and numerical simulations. Presently, ground experiments are performed to finalize the design and the experimental procedures and to guarantee the accuracy of the measurements. These experiments also provide reference data for the study of solidification microstructure dynamics in the presence of buoyancy-driven natural convection. Recent progress is presented concerning the control of the interface shape (critical for pattern analysis), the selection of single crystal of defined orientation (critical for dendritic growth) and the analysis of the dendrite shape.

Competitive Phase Selection in Fe-Ni Alloy Droplets

1995 ◽  
Vol 398 ◽  
Author(s):  
F. Gärtner ◽  
A. F. Norman ◽  
H. Assadi ◽  
A. L. Greer
Keyword(s):  
Free Energy ◽  
Interfacial Energy ◽  
Kinetic Modelling ◽  
Primary Phase ◽  
Drop Tube ◽  
Phase Selection ◽  
Ni Alloys ◽  
Ni Alloy ◽  
Bcc Phase ◽  
Selection Of

ABSTRACTIn the solidification of Fe-Ni droplets (≤ 30 at.% Ni), the selection of different microstructures is dominated by the competition between the bcc and ccp phases. In drop-tube experiments ccp is the primary phase in some dilute (up to 7at% Ni) alloys although the bcc phase is favoured by a lower free energy and by a lower interfacial energy with the liquid. Competitive dendrite growth is a possible explanation for the formation of primary ccp. Comprehensive thermodynamic (CALPHAD) and kinetic modelling is undertaken to understand the growth competition. The origin of the observed primary phases is discussed.

scholarly journals Effects of Withdrawal Rate on the Microstructure of Directionally Solidified GH4720Li Superalloys

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 771
Author(s):  
Jinglong Qu ◽  
Shufeng Yang ◽  
Zhengyang Chen ◽  
Jingshe Li ◽  
Anping Dong ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Electron Probe ◽  
Phase Distribution ◽  
Growth Zone ◽  
Withdrawal Rate ◽  
Directionally Solidified ◽  
Alloying Element ◽  
Stable Growth ◽  
Average Size ◽  
Scanning Electron

Increasing the ingot size of GH4720Li superalloys makes it difficult to control their microstructure, and the withdrawal rate is an important factor in controlling and refining the microstructure of GH4720Li superalloys. In this study, GH4720Li superalloy samples were prepared via Bridgman-type directional solidification with different withdrawal rates. The morphology and average size of the dendrites in the stable growth zone during directional solidification in each sample, morphology and average size of the γ’ phases, and microsegregation of each alloying element were analyzed using optical microscopy, Photoshop, Image Pro Plus, field emission scanning electron microscopy, and electron probe microanalysis. Increasing the withdrawal rate significantly helped in refining the superalloy microstructure; the average secondary dendrite arm spacing decreased from 133 to 79 µm, whereas the average sizes of the γ’ phases in the dendrite arms and the interdendritic regions decreased from 1.02 and 2.15 µm to 0.69 and 1.26 µm, respectively. Moreover, the γ’ phase distribution became more uniform. The microsegregation of Al, Ti, Cr, and Co decreased with the increase in the withdrawal rate; the segregation coefficients of Al, Cr, and Co approached 1 at higher withdrawal rates, whereas that of Ti remained above 2.2 at all the withdrawal rates.

scholarly journals An in-situ method to estimate the tip temperature and phase selection of secondary Fe-rich intermetallics using synchrotron X-ray radiography

2018 ◽  
Vol 149 ◽  
pp. 44-48 ◽  
Author(s):  
S. Feng ◽  
E. Liotti ◽  
A. Lui ◽  
S. Kumar ◽  
A. Mahadevegowda ◽  
...  
Keyword(s):  
Phase Selection ◽  
X Ray ◽  
In Situ Method ◽  
Selection Of

scholarly journals Microstructure Evolution and Mechanical Properties of FeCoCrNiCuTi0.8 High-Entropy Alloy Prepared by Directional Solidification

Entropy ◽  
2020 ◽  
Vol 22 (7) ◽  
pp. 786
Author(s):  
Yiku Xu ◽  
Congling Li ◽  
Zhaohao Huang ◽  
Yongnan Chen ◽  
Lixia Zhu
Keyword(s):  
Mechanical Properties ◽  
Plastic Strain ◽  
Directional Solidification ◽  
Primary Dendrite ◽  
Dendrite Spacing ◽  
Withdrawal Rate ◽  
High Entropy Alloy ◽  
High Entropy ◽  
S 100 ◽  
Solid Liquid Interface

A CoCrCuFeNiTi0.8 high-entropy alloy was prepared using directional solidification techniques at different withdrawal rates (50 μm/s, 100 μm/s, 500 μm/s). The results showed that the microstructure was dendritic at all withdrawal rates. As the withdrawal rate increased, the dendrite orientation become uniform. Additionally, the accumulation of Cr and Ti elements at the solid/liquid interface caused the formation of dendrites. Through the measurement of the primary dendrite spacing (λ1) and the secondary dendrite spacing (λ2), it was concluded that the dendrite structure was obviously refined with the increase in the withdrawal rate to 500 μm/s. The maximum compressive strength reached 1449.8 MPa, and the maximum hardness was 520 HV. Moreover, the plastic strain of the alloy without directional solidification was 2.11%, while the plastic strain of directional solidification was 12.57% at 500 μm/s. It has been proved that directional solidification technology can effectively improve the mechanical properties of the CoCrCuFeNiTi0.8 high-entropy alloy.

Eutectic Growth in Unidirectionally Solidified Fe-Cr-Ni Alloy

1997 ◽  
Vol 481 ◽  
Author(s):  
Toshimitsu Okane ◽  
Takateru Umeda
Keyword(s):  
Growth Rate ◽  
Selection Criterion ◽  
Eutectic Growth ◽  
Interface Temperature ◽  
Competitive Growth ◽  
Directionally Solidified ◽  
Phase Selection ◽  
Rate Condition ◽  
Phase Prediction ◽  
Coupled Growth

ABSTRACTIn this report, transition of solidified phases for directionally solidified Fe-Cr-Ni alloys has been investigated in low growth rate range by using Bridgman type furnace. The ferrite-austenite eutectic growth has been confirmed like a plane front growth of ferrite single phase under low growth rate condition. The transition velocity between eutectic and ferrite cell growth has a good agreement with the result of calculation based on the phase selection criterion and the interface temperature calculation for ferrite, austenite and eutectic phases. These results show that the phase prediction by calculating interface temperature can be applied not only to competitive growth between single phases like peritectic systems, but also to eutectic systems. Furthermore, under the condition of eutectic coupled growth to be occurred in steady state, the changes of solidified phases and their morphologies in the initial transient are discussed.

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.

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