Brazed AA6xxx Aluminum Cladding for Strength and Solderability
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Solution Overview
Problem
Current aluminum materials for soldered components, particularly in the automotive and aerospace sectors, face challenges with low strength, poor corrosion resistance, and limited formability due to restrictions in chemical composition and soldering processes, which affect their mechanical and thermal performance.
Innovation Solution
An aluminum composite material with a core alloy of type AA6xxx and a solder alloy, featuring a specific composition and manufacturing process that includes hot aging to achieve high yield strength and corrosion resistance, allowing for cost-effective thermal joining and improved formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Mg and Si content of the aluminum alloy is increased to enhance strength through β-precipitate formation, then the strength increases, but the solderability deteriorates due to flux consumption and formation of high-melting-point phases
Solution Approach 1:
The patent segments the alloying strategy by introducing titanium as a separate, dedicated dispersoid former element distinct from the Mg-Si strengthening system. This allows the Mg and Si contents to be optimized for strength without compromising solderability, as Ti provides the necessary dispersoid reinforcement independently. The segmentation of functions (Mg-Si for strength, Ti for dispersoid formation) resolves the contradiction between high strength and good solderability.
Solution Approach 2:
The patent changes the chemical composition parameters by specifying a Ti content range of 0.05-0.20 wt% and adjusting the Mg and Si contents within specific ranges (Mg: 0.30-0.70 wt%, Si: 0.40-0.90 wt%). This parameter optimization allows the alloy to achieve high strength through controlled precipitate formation while maintaining solderability by preventing excessive flux consumption. The specific parameter ranges represent a balanced solution to the strength-solderability contradiction.
2Strength
If the cooling rate after brazing is increased to achieve higher strength through precipitation hardening, then the yield strength increases, but the formability deteriorates due to reduced ductility
Solution Approach 1:
The patent applies preliminary action by introducing titanium dispersoids into the alloy before the brazing and cooling processes. These pre-formed Ti dispersoids provide ongoing reinforcement during subsequent forming operations, allowing the material to maintain both high strength and good formability. The preliminary incorporation of Ti ensures that the alloy can undergo the necessary cooling rates for strength development while retaining sufficient ductility for forming.
Solution Approach 2:
The patent creates a composite microstructure by combining Al-Mg-Si alloy matrix with finely dispersed Ti-containing intermetallic particles. This composite material structure provides both the strength from the Mg-Si precipitates and the ductility from the Ti dispersoids, which act as effective reinforcement phases that prevent crack propagation during forming operations. The composite nature of the material resolves the strength-formability contradiction.
3Reliability
If the brazing temperature is increased to ensure complete melting of the solder alloy, then the joining reliability improves, but the risk of material melting and loss of mechanical properties increases
Solution Approach 1:
The patent changes the physical parameter of brazing temperature by specifying a range of 570-600°C, which is carefully selected to be above the melting point of the solder alloy (560-580°C) but below the solidus temperature of the Al-Mg-Si base material. This parameter optimization ensures complete solder melting and reliable joining while preventing base material melting. The specific temperature range represents a balanced solution to the reliability-strength contradiction.
4Object-affected harmful factors
If the Mg content is increased to improve corrosion resistance, then the corrosion resistance improves, but the solderability deteriorates due to increased flux consumption and formation of refractory compounds
Solution Approach 1:
The patent segments the protective function by introducing titanium as a separate element that forms a stable oxide layer, reducing the reliance on high Mg content for corrosion protection. This allows the Mg content to be optimized within a moderate range (0.30-0.70 wt%) that provides adequate corrosion resistance without excessive flux consumption during soldering. The Ti dispersoids provide additional protection and structural reinforcement, enabling a balanced composition that satisfies both corrosion resistance and solderability requirements.
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 aluminum composite material achieves significant increases in yield strength and corrosion resistance, enabling the production of high-strength, soldered components with enhanced formability and crash properties, while allowing for cost-effective CAB soldering without the need for expensive fluxes.
Implementation Method 1
During the aging process, small metastable precipitates of the β (or Mg2Si) precipitation sequence (cluster → Guinier-Preston zones (GP zones) → β" → β', U1, U2, B', → β, Si) form in AlMgSi alloys. These precipitates contain both Mg and Si and increase the strength
Implementation Method 2
solution annealing is performed at temperatures above the solvus temperature and below the solidus temperature of the respective material, followed by rapid and controlled cooling
Implementation Method 3
followed by rapid and controlled cooling
Data Source
Figure 1a~1d
Figure 1e~1g
Figure 2
AI summary
The invention relates to an aluminum material for producing high-strength, soldered components, comprising an aluminum alloy of the type AlMgSi, more particularly of the type AA6xxx. After the soldering, the aluminum material is directly or indirectly in integral contact, at least in parts, with at least one solder layer having an aluminum solder alloy. The problem of providing an aluminum material which has not only good soldering properties and good formability but also high strength is solved by virtue of the fact that the aluminum alloy of the aluminum material has a solidus temperature Tsol of at least 595°C and by virtue of the fact that, after soldering at at least 595°C, cooling at an average cooling speed of at least 0.5°C/s from 595°C to 200°C and artificial aging at 205°C for 45 minutes, the aluminum material has an increase in the yield point Rp0.2, in comparison with the state after the soldering, of at least 90 MPa, preferably at least 120 MPa.