Cu-Co-Si Alloy Strength Conductivity Balance
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Solution Overview
Problem
Cu—Co—Si alloys have not received sufficient investigation for improving characteristics such as electrical conductivity, strength, and bending workability, with second phase particles precipitating easily due to lower solid solubility and larger atomic radius differences, affecting alloy properties.
Innovation Solution
Control of second phase particles by allowing mild cooling through the recrystallization temperature region, maintaining coarse grains, and employing low working ratio cold rolling and high-temperature aging treatments, with Co and Si composition between 0.5% to 4.0% and 0.1% to 1.2% by mass, respectively, and a Co/Si ratio of 3.5 to 5.5, to achieve balanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Co and Si are added to copper alloy, then strength is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent optimizes the composition parameters by limiting Co to 0.5-4.0 mass% and Si to 0.1-1.2 mass%, with Co/Si ratio controlled at 3.5-5.5. This parameter optimization ensures that strength enhancement from Co-Si intermetallic compounds is achieved while minimizing the detrimental effect on electrical conductivity by controlling the total amount of alloying elements.
Solution Approach 2:
The patent creates a composite microstructure consisting of a copper matrix with dispersed Co-Si intermetallic compounds. This composite structure allows the material to benefit from the high strength of intermetallic compounds while maintaining the high electrical conductivity of the copper matrix, resolving the contradiction between strength and conductivity.
2Strength
If second phase particles are precipitated, then strength is improved, but bending workability deteriorates
Solution Approach 1:
The patent promotes discontinuous precipitation along grain boundaries rather than uniform distribution throughout the material. This local quality approach concentrates the strengthening effect at grain boundaries while keeping the interior of grains relatively free of coarse particles, thereby maintaining bending workability while achieving strength enhancement.
Solution Approach 2:
The patent applies partial precipitation rather than complete precipitation throughout the material. By controlling the aging treatment to achieve only discontinuous precipitation along grain boundaries and avoiding excessive precipitation in the grain interiors, the material achieves sufficient strength while preserving ductility and bending workability.
3Reliability
If aging treatment is conducted at high temperature, then electrical conductivity is improved, but strength decreases due to overage softening
Solution Approach 1:
The patent performs discontinuous precipitation along grain boundaries as a preliminary action before the main aging treatment. This preliminary precipitation establishes a stable microstructure that is less susceptible to overage softening during subsequent high-temperature aging, allowing the material to achieve high electrical conductivity without significant strength loss.
Solution Approach 2:
The discontinuous precipitation along grain boundaries acts as a cushioning mechanism that prevents excessive coarsening of precipitates during high-temperature aging. This beforehand cushioning effect stabilizes the microstructure against overage softening, enabling the material to withstand high-temperature aging treatments that improve electrical conductivity while maintaining strength.
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 Cu—Co—Si alloy achieves improved strength, electrical conductivity, and bending workability with suppressed overage softening and reduced strength fluctuations due to controlled discontinuous precipitation, resulting in enhanced production stability and heat resistance.
Implementation Method 1
In a precipitation hardened copper alloy, as a supersaturated solid solution that has been solution heat treated is subjected to an aging treatment, fine precipitates are uniformly dispersed, so that the strength of the alloy increases
Implementation Method 2
as a supersaturated solid solution that has been solution heat treated
Implementation Method 3
conducting quenching, and conducting an aging treatment as necessary
Data Source
AI summary
A Cu—Co—Si alloy having an improved balance between electrical conductivity and strength is provided. Disclosed is a copper alloy for electronic materials, which contains 0.5% to 4.0% by mass of Co and 0.1% to 1.2% by mass of Si, with the balance being Cu and unavoidable impurities, and in which the mass % ratio of Co and Si (Co/Si) is 3.5≦Co/Si≦5.5, an area ratio of discontinuous precipitation (DP) cells is 5% or less, and an average value of a maximum width of discontinuous precipitation (DP) cells is 2 μm or less.