Al-Cu-Li Alloy Sheets for Fuselage Panels
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Solution Overview
Problem
Current aluminum-copper-lithium alloy sheets for aeronautical applications lack improved toughness and mechanical strength, particularly in the L-T direction, when tested on wide panels, and fail to predict optimal properties for damage tolerance sizing due to limitations in existing characterization methods.
Innovation Solution
An aluminum-based alloy with specific composition (2.6-3.0% Cu, 0.5-0.8% Li, 0.1-0.4% Ag, 0.2-0.5% Mg, 0.06-0.20% Zr, and optional elements like Mn, V, Cr, Sc, Hf) is produced through a process involving casting, homogenization, hot rolling, and controlled tempering to achieve an elastic limit of 395-435 MPa in the longitudinal direction, enhancing toughness and mechanical strength on wide panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional aluminum-copper-lithium alloy compositions are used, then manufacturing is simplified, but toughness and mechanical strength on wide panels are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the alloy (Cu: 2.8-3.8%, Li: 0.8-1.3%, Mg: 0.6-1.0%, Ag: 0.0-0.5%, Zr: 0.05-0.18%, Mn: 0.0-0.5%) and the tempering parameters (temperature and duration) to achieve optimal toughness and mechanical strength on wide panels while managing composition complexity
Solution Approach 2:
The patent uses composite material principles by combining multiple alloying elements (Cu, Li, Mg, Ag, Zr, Mn) in specific proportions to create an aluminum-based composite alloy that achieves superior mechanical properties and toughness on wide panels compared to conventional single-element additions
2Measurement precision
If panel width for toughness characterization is limited to ≤760 mm, then testing is simplified, but damage tolerance sizing for actual fuselage applications cannot be accurately predicted
Solution Approach 1:
The patent addresses the dimensionality limitation by developing composition and tempering parameter relationships that account for scale effects, enabling toughness prediction for large-scale fuselage panels (several meters wide) based on controlled testing, thereby bridging the gap between small-scale characterization and large-scale application
3Strength
If higher lithium content is added to increase mechanical strength, then strength improves, but toughness deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the lithium content parameter within a specific range (0.8-1.3%) and combining it with controlled amounts of other elements (Mg: 0.6-1.0%, Cu: 2.8-3.8%) and specific tempering parameters to achieve the optimal balance between mechanical strength and toughness, avoiding the deterioration that occurs with higher lithium content
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 solution provides improved toughness and mechanical strength in the L-T direction on wide panels, meeting the requirements for advanced aeronautical applications by optimizing the elastic limit and tempering conditions, thereby enhancing damage tolerance and corrosion resistance.
Implementation Method 1
solution, quenching and tempering
Implementation Method 2
solution, quenching and tempering
Implementation Method 3
solution, quenching and tempering
Implementation Method 4
the composition and tempering being combined so that the elastic limit in the direction longitudinal R p0.2 (L) is between 395 and 435 MPa
Data Source
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AI summary
The invention concerns a sheet 0.5 to 8 mm thick made from aluminium alloy comprising 2.6 to 3.0% by weight of Cu, 0.5 to 0.8% by weight of Li, 0.1 to 0.4% by weight of Ag, 0.2 to 0.7% by weight of Mg, 0.06 to 0.20% by weight of Zr, 0.01 to 0.15% by weight of Ti, optionally at least one element chosen from Mn, V, Cr, Se, and Hf, the quantity of the element, if chosen, being 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Se, 0.05 to 0.5% by weight for Hf, a quantity of Zn less than 0.2% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, and inevitable impurities at a concentration less than or equal to 0.05% by weight each and 0.15% by weight in total, said sheet being obtained by a method comprising casting, homogenising, hot rolling and optionally cold rolling, solution heat treatment, quenching and tempering, the composition and the tempering being combined in such a way that the elasticity limit in the longitudinal direction Rp0.2(L) is between 395 and 435 MPa. The sheet according to the invention is particularly advantageous for producing aircraft fuselage panels.