In-Situ Gas Jet Cooling for Equiaxed Metal AM Grain Control
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Solution Overview
Problem
Conventional metal additive manufacturing processes result in coarse, elongated grain structures due to directional heat extraction, leading to reduced mechanical properties, anisotropic strength, and fatigue performance, with limited control over solidification and phase transformations, especially in titanium alloys like Ti-6Al-4V.
Innovation Solution
The use of in-situ gas jet impingement during metal additive manufacturing to refine solidification structures by directing cooling gas jets at the melt pool or solidified metal, promoting equiaxed grain growth, blocking epitaxy, and modulating phase transformations, thereby enhancing microstructural control and material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional additive manufacturing processes are used, then fabrication freedom and near-net-shape production are achieved, but coarse elongated grain structures result due to directional heat extraction
Solution Approach 1:
A gas jet system is introduced as an intermediary between the melt pool and the surrounding environment to control heat extraction. The gas jet impingement modifies the cooling rate and thermal gradients, enabling equiaxed grain formation while preserving additive manufacturing's fabrication freedom. This mediator allows independent control of solidification conditions without changing the fundamental layer-by-layer deposition process.
Solution Approach 2:
The invention changes the thermal parameters by applying controlled gas jet impingement to modify heat extraction rates. By adjusting gas flow rate, temperature, and impingement location, the cooling rate and thermal gradient are dynamically controlled during deposition, transforming the solidification structure from elongated columnar to equiaxed grains.
2Strength
If higher cooling rates are applied to refine grain structures, then mechanical properties improve, but deposition rates must be reduced to maintain thermal control
Solution Approach 1:
Gas jet impingement is applied preliminarily during the deposition process itself, rather than as a post-processing step. This allows real-time control of cooling rates and grain formation while material is being deposited, enabling simultaneous achievement of fine grain structures and high deposition rates without requiring slower processing speeds.
Solution Approach 2:
The gas jet system applies localized cooling to specific regions of the melt pool or recently deposited material, creating different thermal conditions in different zones. This local quality control enables refined grain structures in critical areas while maintaining higher deposition rates overall, as cooling is applied only where needed rather than uniformly across the entire build area.
3Manufacturing precision
If post-deposition cooling is used to control phase transformations, then microstructural control is achieved, but cycle time between layers increases
Solution Approach 1:
The gas jet cooling action continues uninterrupted during the entire deposition process and extends into the inter-layer period. This continuous useful action maintains controlled cooling rates through the critical phase transformation temperature ranges without requiring pauses in deposition, thereby achieving microstructural control while preserving rapid cyclic deposition rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in improved mechanical properties, including increased strength, fatigue resistance, and ductility, with refined grain structures comparable to mechanically worked metals, while allowing for higher deposition rates and more complex shape fabrication.
Implementation Method 1
in situ gas jet impingement... directing cooling gas jets at the melt pool or solidified metal
Implementation Method 2
refine solidification structures by directing cooling gas jets at the melt pool... promoting equiaxed grain growth, blocking epitaxy
Implementation Method 3
modulating phase transformations... control over all relevant phase transformations in every deposited layer
Data Source
AI summary
Provided are a jet device and systems and methods using the jet device for manufacturing objects by additive manufacturing, especially titanium and titanium alloy objects, wherein the jet device directs a cooling gas across a liquid molten pool, or to impinge on the liquid molten pool, or to impinge upon a solidified material adjacent to a liquid-solid boundary of the liquid molten pool, or to impinge on an as-solidified material, or any combination thereof, during the additive manufacturing process. The application of the cooling gas can result in an additively manufactured metal product having refined grain structure with a high proportion of the grains being approximately equiaxed, and can yield an additively manufactured product exhibiting improvements in strength, fatigue resistance, and durability.