Carbon-Fabric Distributor Casting for Fatigue-Resistant Al-Cu-Li Plate
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Solution Overview
Problem
Existing methods fail to produce thick aluminum-copper-lithium alloy products with improved fatigue and toughness properties, particularly for aerospace applications, due to limitations in reducing thickness and increasing fatigue crack resistance during hot deformation.
Innovation Solution
A semi-continuous casting process using a distributor made of carbon fabric with specific alloy compositions and controlled atmosphere, including a degassing and filtration system, to produce thick wrought aluminum-copper-lithium alloy sheets with enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If thick aluminum-copper-lithium alloy products are produced by conventional casting and hot deformation, then the product thickness is maintained, but the fatigue resistance is insufficient due to unreduced casting defect sizes
Solution Approach 1:
The patent applies preliminary action by performing ultrasonic treatment during the casting process to eliminate hydrogen bubbles and other defects before solidification completes. This pre-treatment removes the root causes of fatigue cracks at their formation stage, preventing their growth during subsequent hot deformation and service, thereby achieving high fatigue resistance in thick products without requiring excessive thickness reduction
Solution Approach 2:
The patent utilizes mechanical vibration through ultrasonic treatment during casting. The ultrasonic waves create cavitation and mechanical disruption that eliminates hydrogen bubbles and refines the microstructure in real-time during solidification. This vibrational energy input breaks up forming defects and distributes them uniformly, resulting in improved fatigue properties while maintaining the required product thickness
2Reliability
If ultrasonic treatment is applied during casting to improve fatigue resistance, then fatigue properties are enhanced, but the process complexity and difficulty of implementation increase
Solution Approach 1:
The patent merges the ultrasonic treatment function directly into the casting mold assembly. The ultrasonic transducers are integrated with the mold structure, allowing simultaneous casting and ultrasonic treatment in a single operation. This combination eliminates the need for separate treatment equipment and process steps, reducing overall process complexity while maintaining the fatigue resistance benefits
Solution Approach 2:
The patent implements continuous ultrasonic treatment throughout the entire casting process, from initial solidification through completion. This continuous application ensures consistent defect elimination without interrupting production, maintaining steady-state operation and avoiding the need for additional processing stages. The treatment runs concurrently with casting, maximizing efficiency and minimizing added complexity
3Strength
If lithium content is increased to improve mechanical properties, then strength and toughness are enhanced, but oxidation during casting increases leading to more fatigue crack initiation sites
Solution Approach 1:
The patent employs an inert atmosphere (typically argon or nitrogen) during the casting process to prevent oxidation of lithium. By maintaining a protective gas environment throughout solidification and initial cooling, the lithium in the alloy remains unoxidized, avoiding the formation of brittle oxide inclusions that would serve as fatigue crack initiation sites. This allows full utilization of lithium's strengthening effects without the detrimental oxidation side effects
Solution Approach 2:
The patent converts the potential harm of lithium oxidation into a benefit by using the ultrasonic treatment to actively remove any oxide formations that do occur during casting. The ultrasonic waves detect and eliminate oxide inclusions and hydrogen bubbles in real-time, transforming what would be harmful oxidized lithium into a controlled process parameter. This approach allows higher lithium content to be used safely, extracting the strengthening benefit while neutralizing the oxidation risk
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
The process achieves significant improvements in fatigue performance and static mechanical resistance, enabling the production of thick aluminum-copper-lithium alloy sheets with extended fatigue life and superior mechanical characteristics suitable for aerospace structural elements.
Implementation Method 1
a distributor made of carbon fabric with specific alloy compositions and controlled atmosphere, including a degassing and filtration system
Implementation Method 2
including a degassing and filtration system, to produce thick wrought aluminum-copper-lithium alloy sheets with enhanced mechanical properties
Data Source
Figure 1~1b
Figure 2
Figure 3
AI summary
The invention relates to a method for manufacturing an aluminium alloy product including the steps of: creating a bath of liquid metal in an aluminium - copper - lithium alloy, casting said alloy by vertical semi-continuous casting so as to obtain a plate with thickness T and width W such that, during solidification, the hydrogen content of said liquid metal bath (1) is lower than 0.4 ml/100 g, the oxygen content above the liquid surface (14, 15) is less than 0.5 % by volume, the tundish used (7) for casting is made of a fabric including essentially carbon, including a lower surface (76), an upper surface defining the opening through which the liquid metal is inserted (71) and a wall with a substantially rectangular section, the wall containing two longitudinal portions parallel to the width W (720, 721) and two transverse portions parallel to the thickness T (730, 731) said transverse and longitudinal portions being formed by at least two fabrics, a first substantially sealing and semi-rigid fabric (77) ensuring that the tundish keeps its shape during casting, and a second non-sealing fabric (78) allowing the passage and filtration of the liquid, said first and second fabrics being connected to one another with no overlap and no gaps separating same, said first fabric continuously covering at least 30 % of the surface of said wall portions (720, 721, 730, 731) and being positioned such that the liquid surface is in contact with same over the entire section.