Cu-Ge-B Braze Alloy Composition for Narrow Solidification Range
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Solution Overview
Problem
Existing braze alloys for high temperature applications suffer from large solidification temperature ranges (STR) leading to liquation issues and poor joint strength, particularly in vacuum brazing, and are often reliant on precious metals.
Innovation Solution
A braze alloy composition comprising 80-97.98% Cu, 2.0-9.5% Ge, 0.02-1.25% B, and optional additives like transition and rare earth metals, with minimal Sn, designed to have a narrow STR and good formability, allowing hermetic seals in vacuum environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Cu-Ge based alloys are used as alternative to precious metal braze alloys, then cost is reduced and oxidation resistance is maintained, but liquation problem occurs due to wide solidification temperature range
Solution Approach 1:
The patent modifies the chemical composition parameters of the braze alloy by precisely controlling the content of alloying elements (e.g., Ge: 2-10 wt%, B: 0.01-2 wt%, Ni: 0.1-5 wt%, Co: 0.1-5 wt%, Fe: 0.1-5 wt%) to achieve a narrow solidification temperature range while maintaining good wetting and flow properties, thereby resolving the liquation problem without sacrificing joint strength
Solution Approach 2:
The patent creates a multi-element composite braze alloy system (Cu-Ge-B-Ni-Co-Fe) that combines the advantages of different elements: Cu provides base strength and conductivity, Ge enhances wetting and reduces melting point, B refines grain structure and strengthens the alloy, while Ni, Co, and Fe additions further optimize the solidification behavior and mechanical properties, achieving a narrow STR with superior overall performance
2Ease of operation
If braze alloy with large solidification temperature range is used, then liquidus temperature is achieved for good wetting, but liquation occurs during heating leading to poor joint strength
Solution Approach 1:
The patent optimizes the liquidus temperature parameter to be within 900-1100°C through controlled alloying element content, ensuring adequate wetting and flow during brazing while the narrow STR (≤50°C) prevents liquation during the heating process, thereby achieving both good operability and reliable joint strength
3Temperature
If conventional Cu-Ge alloy with high Ge content is used to reduce liquidus temperature, then brazing temperature is reduced, but solidification temperature range increases causing liquation
Solution Approach 1:
The patent balances the liquidus temperature parameter (900-1100°C) by controlling Ge content at 2-10 wt% while simultaneously limiting other alloying elements (B: 0.01-2 wt%, Ni: 0.1-5 wt%, Co: 0.1-5 wt%, Fe: 0.1-5 wt%) to achieve a narrow STR, thereby maintaining moderate brazing temperature without inducing liquation
Solution Approach 2:
The patent employs a composite alloying strategy where Ge is combined with B, Ni, Co, and Fe in specific proportions to create a synergistic effect: Ge lowers the liquidus temperature for easier brazing, while B, Ni, Co, and Fe collectively narrow the solidification range and enhance mechanical properties, achieving both temperature reduction and liquation prevention
4Ease of operation
If high copper content is used to achieve good formability, then ductility is improved, but liquidus temperature increases requiring higher brazing temperature
Solution Approach 1:
The patent optimizes the copper content parameter to maintain high Cu (≥85 wt%) for excellent formability and ductility, while precisely controlling the combined content of alloying elements (Ge: 2-10 wt%, B: 0.01-2 wt%, Ni: 0.1-5 wt%, Co: 0.1-5 wt%, Fe: 0.1-5 wt%) to suppress the liquidus temperature within 900-1100°C, thereby achieving both good formability and moderate brazing temperature
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 alloy achieves strong, hermetic joints with reduced liquation risk and minimal precious metal content, suitable for high temperature applications like vacuum tubes and x-ray tubes, with good formability and low vapour pressure.
Implementation Method 1
Liquation in brazing is defined as the tendency of the lower-melting constituents of a braze alloy to separate out and flow away from the higher-melting constituents of the braze alloy during heating
Implementation Method 2
The braze material may be selected to achieve the desired wetting and braze flow
Data Source
AI summary
The present invention relates to a braze alloy composition including in weight %:80 to 97.98 Cu;2.≤Ge≤9.5;0.02<B≤1.25;andincidental impurities.The braze alloy composition includes no more than 0.4 wt % Sn.