Cryogenic Melt-Pool Cooling in Additive Manufacturing of Aluminum Alloys
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Solution Overview
Problem
The adoption of wire-based additive manufacturing processes for aluminum alloys is limited by the need for solution heat treatment, which causes distortion and residual stresses, and the inability to produce highly alloyed compositions cost-effectively.
Innovation Solution
An additive manufacturing apparatus and method that incorporates cryogenic cooling to achieve rapid solidification rates, allowing for in-situ solution heat treatment and production of highly alloyed compositions, using a system that directs energy onto a workpiece, feeds additional material into a melt-pool, and cryogenically cools the liquid melt-pool to achieve cooling rates of at least 100°C per second.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional solution heat treatment with quenching is applied to aluminum alloys, then the strength of the alloy is improved through supersaturated solid solution formation, but substantial distortion and residual stresses occur
Solution Approach 1:
The invention changes the cooling parameter from conventional quenching to controlled cooling at rates between 10-1000°C per second. This parameter modification allows the formation of supersaturated solid solution without the thermal shock of quenching, thereby achieving strength improvement while minimizing distortion and residual stresses
Solution Approach 2:
The invention performs solution treatment and cooling as an integrated preliminary action during the additive manufacturing process itself, rather than as a separate post-processing step. The controlled cooling is applied immediately after deposition while the part is still in the build chamber, preventing distortion before it occurs
2Strength
If rapid solidification rates are used to produce highly alloyed compositions, then mechanical properties and corrosion resistance are enhanced, but the manufacturing cost increases significantly
Solution Approach 1:
The invention merges the rapid solidification process with wire-based additive manufacturing into a single integrated process. By combining these two previously separate operations, the invention achieves the mechanical properties of rapid solidification processed alloys while using the cost-effective wire feedstock and additive manufacturing approach, thereby reducing overall manufacturing cost
Solution Approach 2:
The invention modifies the cooling rate parameter within the additive manufacturing process to achieve rapid solidification effects. By adjusting the cooling rate to 10-1000°C per second, the invention produces highly alloyed compositions with enhanced mechanical properties without requiring separate expensive rapid solidification processing equipment
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 enables the production of solution heat-treated aluminum alloys with reduced distortion and residual stresses, and allows for the cost-effective production of highly alloyed compositions, enhancing mechanical properties and reducing manufacturing limitations.
Implementation Method 1
cryogenically cooling the liquid melt-pool, thereby to achieve a cooling rate of the liquid melt pool of at least about 100°C per second and to cause the liquid melt-pool to solidify
Implementation Method 2
The solution treatment process creates what is known as a 'supersaturated solid solution' of alloy elements randomly distributed within the aluminium matrix
Implementation Method 3
applying, by a heat source, heat to a portion of a surface of a workpiece sufficient to melt said portion
Implementation Method 4
directing energy onto a growth surface of a workpiece to form thereon a liquid melt-pool
Implementation Method 5
The age hardening process (also referred to as 'precipitation hardening') increases the strength of the alloy by promoting the formation of precipitates from the super saturated solid solution by the diffusion of solute atoms (the alloy additions) dispersed in the solvent (the aluminium matrix)
Data Source
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AI summary
Additive manufacturing apparatus for fabricating a three-dimensional object, the apparatus comprising: means for directing energy onto a growth surface of a workpiece to form thereon a liquid melt-pool; means for feeding additional material into the melt-pool so as to cause the additional material to become incorporated into the liquid of the melt-pool; and means for cryogenically cooling the liquid melt-pool, thereby to achieve a cooling rate of the liquid melt pool of at least 100°C per second and to cause the liquid melt-pool to solidify.