Dissimilar Metal Joint Strength via Laser Molten Zone Control
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Solution Overview
Problem
Dissimilar metal joints between copper and aluminum materials face reduced joint strength due to the formation of hard and brittle intermetallic compounds, and existing methods either require complex structures or reduce joint area, making it difficult to achieve base material strength in applications like in-vehicle battery modules.
Innovation Solution
A dissimilar metal joined body is formed by partially overlapping copper and aluminum materials and irradiating them with a laser beam to create a continuous molten mixed portion where aluminum flows into copper, optimizing the depth and width of this portion to enhance joint strength, while minimizing intermetallic compound deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is performed between copper and aluminum materials, then the two dissimilar metals are joined, but hard and brittle intermetallic compounds are formed reducing joint strength
Solution Approach 1:
The patent applies parameter changes by precisely controlling laser welding parameters (power, speed, focal position) to limit the depth of the molten mixed portion to 5-30 μm. This parameter control prevents excessive intermetallic compound formation while maintaining adequate joint strength, resolving the contradiction between achieving strong joints and avoiding harmful intermetallic compounds.
Solution Approach 2:
The patent uses partial action by creating a limited-depth molten mixed portion rather than complete mixing of the dissimilar metals. The molten mixed portion is controlled to extend only 5-30 μm into the copper material, which is sufficient to achieve base material strength level joints without generating excessive harmful intermetallic compounds that would occur with deeper mixing.
2Strength
If clad material is used to join copper and aluminum, then joint strength is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the need for separate clad materials by directly creating a controlled molten mixed portion between the copper and aluminum base materials. The laser welding process itself generates the necessary transition zone (5-30 μm deep) without requiring pre-fabricated clad layers, thereby simplifying the overall structure and reducing manufacturing complexity.
Solution Approach 2:
The patent uses the laser-induced molten mixed portion as an intermediary between copper and aluminum materials. This molten mixed portion, controlled to 5-30 μm depth, serves as the bonding interface and transition zone that would otherwise require separate clad materials to provide, thereby eliminating the need for complex multi-layer structures.
3Object-generated harmful factors
If spot-laser welding is used to join copper and aluminum, then intermetallic compound formation is reduced, but joint area and strength are limited
Solution Approach 1:
The patent applies continuity of useful action by using continuous laser welding to create a continuous molten mixed portion along the joint line, rather than discrete spot welds. This continuous molten mixed portion (5-30 μm deep) provides continuous bonding between copper and aluminum, achieving both reduced intermetallic compound formation and sufficient joint area for base material strength level joints.
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 approach increases joint strength to the level of the base material, maintaining ductility and reducing the need for expensive clad materials, thus improving energy density and reducing production complexity in applications like battery modules.
Implementation Method 1
irradiating them with a laser beam to create a continuous molten mixed portion where aluminum flows into copper
Implementation Method 2
part of the aluminum material is melted and flows into the copper material
Implementation Method 3
part of the aluminum material is melted and flows into the copper material
Data Source
Figure 1
Figure 2
AI summary
A dissimilar metal joined body includes a copper material, an aluminum material and a molten mixed portion. The molten mixed portion is configured so that part of the aluminum material is melted and flows into the copper material. The depth from a surface of the copper material which contacts the aluminum material in the molten mixed portion is at least 5 µm and no greater than 30 µm.