Dissimilar Metal Bonding with Graded Interlayer Composition

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Solution Overview

Problem

Bonding dissimilar metals like aluminum and iron is challenging due to the formation of weak intermetallic compounds and significant thermal stress at the bonded interface, leading to cracks and difficulties in melting welding, while mechanical bonding methods face issues with increased weight and strength shortages.

Innovation Solution

A method involving the sequential formation of dissimilar metal layers using a mixed filler material with particles of a second metal having a higher melting point, where the proportion and particle size of the second metal are adjusted in each layer to increase bonding strength, and the use of a wire for the first metal to avoid diffusion and adjust supply amounts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If melting welding is used to bond dissimilar metals like aluminum and iron, then bonding strength is improved, but cracks are generated at the interface due to thermal stress and intermetallic compound formation

Engineering Contradiction:

Improvebonding strengthVSAvoidinterface integrity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The bonding process is segmented into multiple stages: first forming a dissimilar metal layer with controlled composition, then forming a second metal layer, and finally welding. This segmentation allows each stage to optimize for its specific function, preventing crack formation while achieving strong bonding.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Before welding, the dissimilar metal layer is pre-formed with a specific composition gradient and the second metal layer is deposited. This preliminary action prepares the interface structure in advance, ensuring that when welding occurs, the thermal stress and intermetallic compound formation are controlled and do not cause cracking.

Inventive Principle:

Principle #10Preliminary action

2Weight of moving object

If mechanical bonding method is used, then weight increase occurs, but bonding strength is insufficient

Engineering Contradiction:

Improvebonded joint weightVSAvoidbonding strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

A dissimilar metal layer with controlled composition acts as an intermediary between the two base metals. This intermediate layer facilitates metallurgical bonding while controlling the formation of intermetallic compounds, achieving strong bonding without the weight penalty of mechanical fasteners.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If the proportion of second metal in mixed filler material is increased, then bonding strength is improved, but melting point requirements become more difficult to satisfy

Engineering Contradiction:

Improvebonding strengthVSAvoidmelting point control

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The filler material has non-uniform composition with varying proportions of first and second metals in different regions. The dissimilar metal layer contains a specific composition that allows controlled interaction, while the second metal layer has higher concentration of the high-melting-point metal, optimizing both bonding strength and thermal properties locally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The composition parameters of the filler material are changed across different layers. The dissimilar metal layer uses a composition optimized for interface bonding, while the second metal layer uses a composition optimized for strength and thermal resistance, allowing the system to satisfy melting point requirements while achieving high bonding strength.

Inventive Principle:

Principle #35Parameter changes

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

This method secures required strength and enables effective bonding even in combinations that produce weak intermetallic compounds, enhancing the bonding strength between dissimilar metals by controlling the proportion and melting of the second metal layer.

Implementation Method 1

heating the mixed filler material to a temperature equal to or higher than a melting point of the first metal and equal to or lower than a melting point of the second metal

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the second metal layer and the second metal dispersed in the dissimilar metal layer are welded to each other when the second metal layer is formed

Methodology Applied

Scientific EffectWelding: Welding

Implementation Method 3

the first metal that constitutes the dissimilar metal layer is welded to the first material to be bonded

Methodology Applied

Scientific EffectWelding: Welding

Data Source

PatentUS11235408B2Method for bonding dissimilar metals to each other

Publication Date: 2022.02.01 MITSUBISHI HEAVY IND LTD

AI summary

Provided is a method for bonding dissimilar metals to each other, the method comprising: dissimilar metal layer-forming steps (P2), (P3), (P4) for supplying, to form dissimilar metal layers; a second metal layer-forming step (P5) for supplying, on the surface of the dissimilar metal layers, a filler material formed of a second metal, and heating the filler material formed of the second metal to a temperature equal to or higher than a melting point of the second metal, to form a second metal layer formed of the second metal; and a second material-to-be-bonded welding step (P6) for welding a second material to be bonded that is formed of the second metal, onto the second metal layer.