FURTHER OBSERVATIONS ON DENDRITIC GROWTH IN METALS

1952 ◽  
Vol 30 (5) ◽  
pp. 488-502 ◽  
Author(s):  
F. Weinberg ◽  
Bruce Chalmers
Keyword(s):  
High Purity ◽  
Dendritic Growth ◽  
Cell Structure ◽  
Dendrite Growth ◽  
Initial Part ◽  
Lead Crystal ◽  
Initial Formation ◽  
A Cell ◽  
Solid Liquid Interface ◽  
Solid Liquid

The direction of dendrite growth has been determined as a function of crystallographic orientation for high purity tin and zinc, using a single crystal decanting technique. Measurements are reported on the rate of dendrite growth in lead, and the spacing between dendrite rows of a lead crystal for varying amounts of supercooling. The initial formation of dendrite stalks appears related to a cell structure observed on the exposed solid liquid interface.A mechanism of dendrite growth is advanced and compared with the experimental observations. It is shown that dendritic growth occurs only during the initial part of solidification. The remainder is a result of the nondendritic advance of a solid liquid interface with some thickening of the existing branches.

Numerical Analysis of Aerospace Nickel-Based Single-Crystal Superalloy Weldability Part I: Crystallography-Dependent Dendrite Growth

2021 ◽  
Vol 1018 ◽  
pp. 3-12
Author(s):  
Zhi Guo Gao
Keyword(s):  
Single Crystal ◽  
Weld Pool ◽  
Dendrite Growth ◽  
Liquid Interface ◽  
Solidification Cracking ◽  
Microstructure Development ◽  
Growth Region ◽  
The Right ◽  
Solid Liquid Interface ◽  
Solid Liquid

The thermal-metallurgical modeling of microstructure development was further advanced during single-crystal superalloy weld pool solidification by coupling of heat transfer model, columnar/equiaxed transition (CET) model and multicomponent dendrite growth model on the basis criteria of minimum dendrite velocity, constitutional undercooling and marginal stability of planar front. It is clearly indicated that heat input (laser power and welding speed) and welding configuration simultaneously influence the stray grain formation, columnar/equiaxed transition and dendrite growth. For beneficial (001) and [100] welding configuration, the microstructure development along the solid/liquid interface is symmetrically distributed about the weld pool centerline throughout the weld pool. Finer columnar in [001] epitaxial dendrite growth region is kinetically favored at the bottom of the weld pool. For detrimental (001) and [110] welding configuration, the microstructure development along the solid/liquid interface is asymmetrically distributed. The dendrite trunk spacing along the solid/liquid interface from the beginning to end of solidification morphologically increases on the left side of the weld pool, while it spontaneously decreases on the right side. The vulnerable location of solidification cracking is confined in the [100] dendrite growth region on the right side of the weld pool because of increasing metallurgical contributing factors of severe stray grain formation, centerline grain boundary formation and coarse dendrite size. The mechanism of crystallography-dependent asymmetrical solidification cracking due to microstructure anomalies is proposed. It is crystallographically favorable for predominant morphology instability to deteriorate weldability. Active [100] dendrite growth region is diminished in the shallow elliptical weld pool by optimum low heat input (low laser power and high welding speed) with (001) and [100] welding configuration to essentially facilitate single-crystal solidification conditions and provide enough resistant to solidification cracking. Moreover, the theoretical predictions agree well with the experiment results. The reliable weldability maps are therefore established to determine the prerequisite for successful crack-free laser welding or cladding. The useful model is also applicable for other single-crystal superalloys with similar metallurgical properties.

Evolution of the Solidification Microstructure of Rheocast High Purity Aluminium

2012 ◽  
Vol 192-193 ◽  
pp. 109-115 ◽  
Author(s):  
Sarah George ◽  
Robert Knutsen
Keyword(s):  
High Purity ◽  
Liquid Interface ◽  
Cellular Growth ◽  
Solidification Mode ◽  
Purity Aluminium ◽  
High Purity Aluminium ◽  
Semi Solid ◽  
The Stability ◽  
Solid Liquid Interface ◽  
Solid Liquid

High purity aluminium has been successfully rheocast using the CSIR-RCS system combined with high pressure die casting. Analysis of the as-cast microstructure by SEM and EBSD revealed the presence of in-grain substructures. These morphological features show that the overall growth mode of the globular grains during rheocasting is planar, but the presence of these features indicates that the solidification mode is cellular at some stages during the slurry production process. Cellular solidification is associated with unstable growth at the solid-liquid interface and is initiated and exacerbated by solute gradients between the melt and the newly formed solid. This high purity alloy exhibits the same cellular growth, indicating that even minor solute variations have an effect on the stability of the solid-liquid interface and, hence, the mode of solidification during semi-solid rheocasting.

Prediction of Solid-Liquid Interface Stability and Dendritic Growth in Multi-Component Alloys with Calphad Method

2005 ◽  
Vol 475-479 ◽  
pp. 2721-2724
Author(s):  
Rui Jie Zhang ◽  
Zhi He ◽  
Wan Qi Jie
Keyword(s):  
Experimental Data ◽  
Present Method ◽  
Dendritic Growth ◽  
Calphad Method ◽  
Liquid Interface ◽  
Interface Stability ◽  
Calculation Results ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Good Agreement

A method to predict the solid-liquid interface stability and the constrained dendrite growth of multi-component alloys was developed based on the Calphad method. The method was applied to several industrial Al-Si-Mg alloys, and the predicted results were compared with some former experimental data. The good agreement between the calculation results and the experimental data demonstrates the superiority of the present method to the classical one based on constant parameter assumptions.

Phase-Field Microstructure Solidification of Al–2 wt% Si Alloys

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
J. B. Allen
Keyword(s):  
Directional Solidification ◽  
Phase Field ◽  
Maximum Concentration ◽  
Dendritic Growth ◽  
Interface Energy ◽  
Liquid Interface ◽  
Two Dimensional ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Dilute Alloy

In this work, we develop one- and two-dimensional phase-field simulations to approximate dendritic growth of a binary Al–2 wt% Si alloy. Simulations are performed for both isothermal as well as directional solidification. Anisotropic interface energies are included with fourfold symmetries, and the dilute alloy assumption is imposed. The isothermal results confirm the decrease in the maximum concentration for larger interface velocities as well as reveal the presence of parabolic, dendrite tips evolving along directions of maximum interface energy. The directional solidification results further confirm the formation of distinctive secondary dendritic arm structures that evolve at regular intervals along the unstable solid/liquid interface.

Analysis for free dendritic growth model incorporating the nonisothermal nature of solid–liquid interface

2015 ◽  
Vol 379 (4) ◽  
pp. 237-240 ◽  
Author(s):  
Shu Li ◽  
Zhihui Gu ◽  
Dayong Li ◽  
Shucheng Liu ◽  
Minghua Chen ◽  
...  
Keyword(s):  
Growth Model ◽  
Dendritic Growth ◽  
Liquid Interface ◽  
Solid Liquid Interface ◽  
Solid Liquid

Numerical Analysis of Solidification Behavior during Laser Welding Nickel-Based Single-Crystal Superalloy Part I: Crystallography-Dependent Solid Aluminum Distribution

2021 ◽  
Vol 1020 ◽  
pp. 13-22
Author(s):  
Zhi Guo Gao
Keyword(s):  
Single Crystal ◽  
Weld Pool ◽  
Heat Input ◽  
Dendrite Growth ◽  
Solidification Cracking ◽  
Aluminum Concentration ◽  
Growth Region ◽  
Solid Aluminum ◽  
Solid Liquid Interface ◽  
Solid Liquid

The thermal metallurgical modeling of alloying aluminum redistribution was further developed through couple of heat transfer model, dendrite selection model, multicomponent dendrtie grwoth model and nonequilibrium solidification model during three-dimensional nickel-based single-crystal superalloy weld pool solidification over a wide range of welding conditions (laser power, welding speed and welding configuration) to facilitate understanding of solidification cracking phenomena. It is indicated that the welding configuration plays more important role than heat input in aluminum redistribution. The bimodal distribution of solid aluminum concentration along the solid/liquid interface is crystallographically symmetrical about the weld pool centerline for (001) and [100] welding configuration, while the distribution of solid aluminum concentration along the solid/liquid interface is crystallographically asymmetrical throughout the weld pool for (001) and [110] welding configuration. The size of vulnerable [100] dendrite growth region is beneficially suppressed in favor of epitaxial [001] dendrite growth region through optimum low heat input (low laser power and high welding speed) to facilitate single-crystal dendrite growth for successful crack-free weld at the expense of shallow weld pool geometry. The overall aluminum concentration in (001) and [100] welding configuration is significantly smaller than that of (001) and [110] welding configuration regardless of heat input. Severe aluminum enrichment is confined to [100] dendrite growth region where is more susceptible to solidification cracking. Heat input and welding configuration are optimized in order to minimize the solidification cracking susceptibility and improve microstructure stability. The relationship between welding conditions and alloying aluminum redistribution are established for solidification cracking susceptibility evaluation. The higher heat input is used, the more aluminum enrichment is monotonically incurred by diffusion with considerable increase of metallurgical driving forces for morphology instability and microstructure anomalies to deteriorate weldability and vice versa. The mechanism of asymmetrical solidification cracking because of crystallography-dependent alloying redistribution is proposed. The theoretical predictions agree well with the experiment results. Moreover, the useful modeling is also applicable to other single-crystal superalloys with similar metallurgical properties during laser welding or laser cladding.

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