scholarly journals Mushy Zone Morphology Calculation with Application of CALPHAD Technique

Metals ◽  
2017 ◽  
Vol 7 (9) ◽  
pp. 363 ◽  
Author(s):  
Piotr Mikolajczak ◽  
Amber Genau ◽  
Lorenz Ratke
Keyword(s):  
Mushy Zone ◽  
Calphad Technique

scholarly journals Thermodynamic Assessment of Mushy Zone in Directional Solidification

2015 ◽  
Vol 15 (4) ◽  
pp. 101-109 ◽  
Author(s):  
P. Mikołajczak ◽  
L. Ratke
Keyword(s):  
Mushy Zone ◽  
Phase Diagrams ◽  
Directional Solidification ◽  
Ternary Phase ◽  
Thermodynamic Assessment ◽  
Chemical Compositions ◽  
Calphad Technique ◽  
Ternary Phase Diagrams ◽  
Liquid Channel ◽  
Significant Mass

Abstract Solidification of AlSiFe alloys was studied using a directional solidification facility and the CALPHAD technique was applied to calculate phase diagrams and to predict occurring phases. The specimens solidified by electromagnetic stirring showed segregation across, and the measured chemical compositions were transferred into phase diagrams. The ternary phase diagrams presented different solidification paths caused by segregation in each selected specimen. The property diagrams showed modification in the sequence and precipitation temperature of the phases. It is proposed in the study to use thermodynamic calculations with Thermo-Calc which enables us to visualize the mushy zone in directional solidification. 2D maps based on property diagrams show a mushy zone with a liquid channel in the AlSi7Fe1.0 specimen center, where significant mass fraction (33%) of β-Al5FeSi phases may precipitate before α-Al dendrites form. Otherwise liquid channel occurred almost empty of β in AlSi7Fe0.5 specimen and completely without β in AlSi9Fe0.2. The property diagrams revealed also possible formation of α-Al8Fe2Si phases.

Modeling of a mushy zone during quasi-stationary solidification of TiAl alloy

2020 ◽  
Author(s):  
Olga M. Zhukova ◽  
Irina G. Nizovtseva ◽  
Eugeny V. Pavlyuk ◽  
Ilya O. Starodumov ◽  
Alexander A. Ivanov
Keyword(s):  
Mushy Zone ◽  
Tial Alloy

Comparison of cracking sensitivity between high-permeability 1.5 wt% Si steel and 6.5 wt% Si steel in mushy zone

2020 ◽  
Vol 510 ◽  
pp. 166927
Author(s):  
W.L. Hu ◽  
Y.X. Zhang ◽  
G. Yuan ◽  
X.M. Zhang ◽  
J.H. Zhao ◽  
...  
Keyword(s):  
Mushy Zone ◽  
High Permeability ◽  
Cracking Sensitivity

Permeability in the Mushy Zone

2010 ◽  
Vol 649 ◽  
pp. 399-408 ◽  
Author(s):  
R.G. Erdmann ◽  
D.R. Poirier ◽  
A.G. Hendrick
Keyword(s):  
Mushy Zone ◽  
Volume Fraction ◽  
Primary Dendrite ◽  
Fluid Velocity ◽  
Interdendritic Liquid ◽  
Creeping Flow ◽  
Liquid Region ◽  
Local Volume ◽  
Local Volume Fraction ◽  
Deterministic Function

When modeled at macroscopic length scales, the complex dendritic network in the solid-plus-liquid region of a solidifying alloy (the “mushy zone”) has been modeled as a continuum based on the theory of porous media. The most important property of a porous medium is its permeability, which relates the macroscopic pressure gradient to the throughput of fluid flow. Knowledge of the permeability of the mushy zone as a function of the local volume-fraction of liquid and other morphological parameters is thus essential to successfully modeling the flow of interdendritic liquid during alloy solidification. In current continuum models, the permeability of the mushy zone is given as a deterministic function of (1) the local volume fraction of liquid and (2) a characteristic length scale such as the primary dendrite arm spacing or the reciprocal of the specific surface area of the solid-liquid interface. Here we first provide a broad overview of the experimental data, mesoscale numerical flow simulations, and resulting correlations for the deterministic permeability of both equiaxed and columnar mushy zones. A extended view of permeability in mushy zones which includes the stochastic nature of permeability is discussed. This viewpoint is the result of performing extensive numerical simulations of creeping flow through random microstructures. The permeabilities obtained from these simulations are random functions with spatial autocorrelation structures, and variations in the local permeability are shown to have dramatic effects on the flow patterns observed in such microstructures. Specifically, it is found that “lightning-like” patterns emerge in the fluid velocity and that the flows in such geometries are strongly sensitive to small variations in the solid structure. We conclude with a comparison of deterministic and stochastic permeabilities which suggests the importance of incorporating stochastic descriptions of the permeability of the mushy zone in solidification modeling.

scholarly journals Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xiangjun Xu ◽  
Rui Hu ◽  
Junpin Lin ◽  
Jian Guo
Keyword(s):  
Mushy Zone ◽  
Solidification Rate ◽  
Solidus Temperature ◽  
Melting Zone ◽  
Optical Microscope ◽  
Directionally Solidified ◽  
Good Oxidation Resistance ◽  
Columnar Grains ◽  
Columnar Grain ◽  
Evolution Of Microstructure

High Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solidified (DS) Ti-45Al-8Nb (in atomic percent) alloy prepared at withdrawing rates of 30 μm/s and 200 μm/s and a temperature gradient of 4200 K/m were observed by optical microscope and electronic probe microanalyzer. The microsegregations were characterized by wave dispersive spectroscopy. The results show that the DS ingots include the no melting zone, directionally solidified zone with columnar grains, mushy zone, and quenched liquid zone. The primary dendritic arm spacings are 353 μm and 144 μm, respectively, for the two ingots. But the solidified microstructures of the ingots are large lamellar colonies, which contain a few B2 patches and γ bands induced by microsegregation. From dendritic zone to columnar zone, the volume fractions of B2 patches and γ bands decrease. The segregation extents of Al and Nb decrease with the increase of solidification rate. There exists an obvious back diffusion process of Al during solidification and cooling after solidification. According to evolution of Al concentration profiles from mushy zone to columnar grain zone, interdiffusion coefficient for Al in β-Ti at near solidus temperature is semiquantitatively calculated, and the value is (6 – 11) × 10−11 m2/s.

scholarly journals Evolution of a mushy zone in a static temperature gradient using a volume average approach

2017 ◽  
Vol 141 ◽  
pp. 206-216 ◽  
Author(s):  
A.B. Phillion ◽  
M. Založnik ◽  
I. Spindler ◽  
N. Pinter ◽  
C.-A. Aledo ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Mushy Zone ◽  
Volume Average

scholarly journals A thermodynamic description of metastable c-TiAlZrN coatings with triple spinodally decomposed domains

2017 ◽  
Vol 53 (2) ◽  
pp. 85-93 ◽  
Author(s):  
J. Zhou ◽  
L. Zhang ◽  
L. Chen ◽  
Y. Du ◽  
Z.K. Liu
Keyword(s):  
Experimental Data ◽  
Phase Equilibria ◽  
First Principles ◽  
Thermodynamic Description ◽  
Quantitative Description ◽  
Experimental Phase Equilibria ◽  
Free Energies ◽  
Calphad Technique ◽  
Important Input ◽  
Good Agreement

A critical thermodynamic assessment of the metastable c-TiAlZrN coatings, which are reported to spinodally decompose into triple domains, i.e., c-TiN, c-AlN, and c-ZrN, was performed via the CALculation of PHAse Diagram (CALPHAD) technique based on the limited experimental data as well as the first-principles computed free energies. The metastable c-TiAlZrN coatings were modeled as a pseudo-ternary phase consisting of c-TiN, c-AlN and c-ZrN species, and described using the substitutional solution model. The thermodynamic descriptions for the three boundary binaries were directly taken from either the CALPHAD assessment or the first-principles results available in the literature except for a re-adjustment of the pseudo-binary c-AlN/c-ZrN system based on the experimental phase equilibria in the pseudo-ternary system. The good agreement between the calculated phase equilibria and the experimental data over the wide temperature range was obtained, validating the reliability of the presently obtained thermodynamic descriptions for the c-TiAlZrN system. Based on the present thermodynamic description, different phase diagrams and thermodynamic properties can be easily predicted. It is anticipated that the present thermodynamic description of the metastable c-TiAlZrN coatings can serve as the important input for the later quantitative description of the microstructure evolution during service life.

Motion of bubbles in the mushy zone

2006 ◽  
Vol 55 (10) ◽  
pp. 871-874 ◽  
Author(s):  
Qingyou Han
Keyword(s):  
Mushy Zone
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