Aluminum Clad Sheet Structure for Anodizing High-Strength 7xxx Alloy
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Solution Overview
Problem
7xxx series aluminum alloys, used in electronic device housings for their high strength, face limitations due to lower corrosion resistance and uneven surface treatability issues during anodizing, making them less suitable for portable electronic devices that require both strength and aesthetic appeal.
Innovation Solution
A multi-layer aluminum clad sheet is produced using a 7xxx-series aluminum alloy as the base material and a 6xxx-series or 1xxx-series alloy as the coat material, with thermal treatment and age-hardening processes to enhance adhesion strength and surface properties without compromising the base material's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If 7xxx series aluminum alloy is used as base material for high strength, then mechanical strength is improved, but surface anodizing quality deteriorates due to uneven oxide layer growth
Solution Approach 1:
The aluminum alloy is segmented into a multi-layer clad structure with a 7xxx series high-strength base layer and a 6xxx series anodizable coat layer. This segmentation allows each layer to fulfill its specific function: the base layer provides mechanical strength while the coat layer ensures high-quality anodizing surface treatment.
Solution Approach 2:
The invention creates a composite material system by cladding 6xxx series aluminum alloy (Al-Mg-Si) onto 7xxx series aluminum alloy (Al-Zn-Mg). The composite structure combines the high strength of 7xxx series with the superior anodizing properties of 6xxx series, resolving the contradiction between mechanical strength and surface treatability.
2Strength
If 7xxx series aluminum alloy is used for high specific strength, then mechanical properties are improved, but corrosion resistance deteriorates
Solution Approach 1:
The clad structure segments the material functions, placing the corrosion-resistant 6xxx series alloy as the outer coat layer that directly contacts the environment, while the 7xxx series high-strength alloy remains protected inside as the base material.
Solution Approach 2:
The composite clad sheet combines 6xxx series aluminum alloy with excellent corrosion resistance on the surface with 7xxx series aluminum alloy providing high specific strength in the base, achieving both high strength and reliable corrosion resistance simultaneously.
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 resulting clad sheet achieves superior surface anodizing characteristics, improved corrosion resistance, and enhanced mechanical properties, making it suitable for use in electronic device housings that require both strength and aesthetic appeal.
Implementation Method 1
heating the overlaid layers at 480 °C to 520 °C to soften and rolling the softened layers to join together
Implementation Method 2
heating the layers at 520 °C to 540 °C for 30 minutes or more and then water cooling the layers
Implementation Method 3
heating the layers at the solution-treated layers at 80 °C to 180 °C for eight hours or more and then air-cooling the layers
Data Source
Figure 1
Figure 2
Figure 3A~4
AI summary
According to an embodiment of the present disclosure, an anodizable aluminum clad sheet may comprise a base material including a 7xxx-series aluminum alloy and a coat material including a 6xxx-series aluminum alloy or a 1xxx-series aluminum alloy disposed on one or both front and back surfaces of the base material, wherein the 7xxx-series aluminum alloy includes 4.0% to 8.0% of zinc (Zn) relative to a total weight of the aluminum clad sheet, 1.0 % to 3.0 % of magnesium (Mg) relative to the total weight of the aluminum clad sheet, and the rest being aluminum (Al) and at least one other impurity. According to an embodiment of the present disclosure, a method for manufacturing an aluminum clad sheet may enhance the adhesion strength of the clad sheet by employing thermal treatment after forming the clad sheet and may age-harden the clad sheet without deteriorating strength, thereby achieving superior surface and engineering properties.