Analysis of Competitive Growth Mechanism of Stray Grains of Single Crystal Superalloys during Directional Solidification Process

2011 ◽  
Vol 40 (1) ◽  
pp. 9-13 ◽  
Author(s):  
Zhao Xinbao ◽  
Liu Lin ◽  
Zhang Weiguo ◽  
Qu Min ◽  
Zhang Jun ◽  
...  
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Growth Mechanism ◽  
Solidification Process ◽  
Competitive Growth ◽  
Directional Solidification Process ◽  
Stray Grains

Prediction of Grain Formation and Defects during Solidification in Single Crystal Superalloy Castings

2021 ◽  
Vol 1035 ◽  
pp. 819-826
Author(s):  
Hai Peng Jin ◽  
Shi Zhong Liu ◽  
Hong Ji Xie ◽  
Jia Rong Li
Keyword(s):  
Single Crystal ◽  
Large Deviation ◽  
Solidification Process ◽  
Orientation Distribution ◽  
Single Crystal Superalloy ◽  
Competitive Growth ◽  
Initial Nucleation ◽  
Grain Formation ◽  
Orientation Deviation ◽  
Stray Grains

Numerical simulation and prediction of grain formation and defects, including the stray grain and high angle orientation deviation during directional solidification process of a single crystal superalloy hollow turbine blade are experimentally conducted by means of commercial software ProCAST and backscattering scanning electron microscope. The results show that the initial nucleation amount at the beginning section of the starter block is 104 of magnitude, and the number of grains decreases gradually with the competitive growth, and the number is about 100 at the spiral of the selector. And the orientation distribution of grains is close to <001> direction, with the orientation deviation between 10° and 15°. Moreover, with the increase of withdrawal rate, the curvature of isoline of liquidus of single crystal blade increases, and the tendency to form stray grains defects increases. The grain with a large deviation from orientation blocks the growth of other grains at the first rotating transition site of the selector, and then gradually grows and solidifies to form the final blade.

The Precipitation Behavior of γ′ Phase in Single Crystal Ni-Based DD6 Superalloy for Turbine Blade

2017 ◽  
Vol 898 ◽  
pp. 534-544
Author(s):  
Y.P. Xue ◽  
Jia Rong Li ◽  
Jin Qian Zhao ◽  
J.C. Xiong
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Turbine Blade ◽  
Solidification Process ◽  
Isothermal Solidification ◽  
Single Crystal Superalloy ◽  
Size Difference ◽  
Precipitation Behavior ◽  
Cooling Rates ◽  
Directional Solidification Process

The precipitation behavior of γ′ precipitates in typical section dimensions of DD6 single crystal superalloy turbine blade was investigated experimentally during directional solidification process. The phase transformation temperatures in the single crystal Ni-based DD6 superalloy from DSC analysis and JmatPro simulation were basically in consistent with the isothermal solidification experiments. The solidification route of DD6 single crystal superalloy could be described as follows: L1 → γ + L2; L2 → (γ + γ′)eutectic + MC; γ → γ′/γ. With increasing continuous cooling rates, the primary γ′ precipitates tended to be refined, and the size distributions of the primary γ′ precipitates at every temperature measuring position followed the normal distribution. In comparison to the interdendritic regions, nearly a 60% reduction in the average sizes of the primary γ′ precipitates was measured in the dendritic core regions. The result of the primary γ′ size difference was strongly affected by the multi-component segregations between the interdendritic and dendritic regions, where the γ′ forming elements of Al and Ta segregated towards the interdendritic regions. Furthermore, the secondary γ′ precipitation was found to occur within a relatively wide corridor of γ matrix for low cooling rates (12.6, 23.3 and 29.7 °C/min) during the directional solidification process. The occurrence of the secondary γ′ precipitation resulted from the complex interaction of multiple thermodynamic and kinetic factors in the γ′ nucleation and the diffusion rate of γ′ forming elements.

Numerical Simulation of Binary Alloy Crystal Growth Using Phase-Field Method

2013 ◽  
Vol 842 ◽  
pp. 57-60 ◽  
Author(s):  
Yan Bo Dong ◽  
Ming Chen ◽  
Xi Wang
Keyword(s):  
Crystal Growth ◽  
Directional Solidification ◽  
Binary Alloy ◽  
Phase Field ◽  
Phase Field Model ◽  
Solidification Process ◽  
Phase Field Method ◽  
Columnar Dendrite ◽  
Competitive Growth ◽  
Directional Solidification Process

The competitive growth of multiple dendrites and crystal growth of directional solidification in a Mg-Al binary alloy were simulated using phase-field model, and the effect of undercooling value on the microstructural dendritic growth pattern in directional solidification process was studied in the paper. The simulation results showed the impingement of the adjacent grains, which made the dendrite growth inhibited in the competitive growth of multiple dendrites, and in directional solidification process, quantitative comparison of different undercooling values that predicted the columnar dendrite evolution were carried out. With the increasing of the undercooling value, the dendrite tip radius and second dendrite arms became smaller, and the crystal structure is more uniform and dense.

Directional solidification by appropriate chemically active single crystal seed: An alternative way of generating large superconducting 123 single domain

1997 ◽  
Vol 12 (12) ◽  
pp. 3199-3202 ◽  
Author(s):  
R. Cloots ◽  
Fr. Auguste ◽  
A. Rulmont ◽  
N. Vandewalle ◽  
M. Ausloos
Keyword(s):  
Liquid Phase ◽  
Single Crystal ◽  
Directional Solidification ◽  
Concentration Gradient ◽  
Solidification Process ◽  
Subsequent Growth ◽  
High Concentration ◽  
Dysprosium Oxide ◽  
Directional Solidification Process ◽  
Crystal Seed

A Dy2O3 single crystal has been used as a seed for the growth of isothermally melt-textured Dy-123 material. The nucleation-controlled step has been observed to be related to the heterogeneous nucleation of 211 particles at the surface of the dysprosium oxide single crystal. The subsequent growth mode seems to be controlled by a high concentration gradient of dysprosium in the liquid phase. This leads to a directional solidification process of the 123 phase. The size of the 211 particles seems to decrease as the distance from the dysprosium oxide single crystal increases.

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