Copper Alloy Composition for Strength-Conductivity Balance
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Solution Overview
Problem
Existing copper alloys used in connectors and terminals face challenges in achieving a balance of high electrical conductivity, yield strength, and stress relaxation resistance while maintaining cost-effectiveness, with previous compositions either being too expensive or not providing satisfactory performance due to inadequate consideration of element interactions.
Innovation Solution
A copper alloy comprising specific weight percentages of Cu, Ni, Si, Cr, Sn, Zr, and Zn, with controlled precipitation phases of NiSi and Cr3Si, and optional Co, Fe, P, Re, and Mn, is developed through a controlled melting, casting, and aging process to enhance strength and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Sn element is added to achieve high strength through solid solution strengthening, then yield strength is improved, but electrical conductivity deteriorates (below 20% IACS) and material cost increases
Solution Approach 1:
The patent changes the strengthening mechanism from solid solution strengthening (Sn) to precipitation strengthening (Ni-P, Fe-P compounds). By controlling the precipitation process and phase composition, the alloy achieves high strength (yield strength ≥550 MPa) while maintaining good electrical conductivity (≥35% IACS), resolving the contradiction between strength and conductivity.
Solution Approach 2:
The patent creates a composite microstructure with Cu matrix and dispersed Ni-P, Fe-P precipitation phases. This composite structure provides both the ductility of the Cu matrix and the strength of the precipitation phases, while the controlled phase distribution minimizes impact on electrical conductivity.
2Strength
If Ni and Si elements are added for precipitation strengthening to improve comprehensive performance, then strength and conductivity are improved, but material cost increases due to metal cost
Solution Approach 1:
The patent optimizes the composition parameters by adding P element (0.01-0.05 wt.%) which forms high-strength Ni-P and Fe-P compounds at lower metal concentrations. The controlled precipitation process parameters (temperature, time, cooling rate) enable efficient utilization of alloying elements, reducing overall material cost while achieving yield strength ≥550 MPa.
3Ease of manufacture
If high Zn content (10-20%) is added to Cu-Zn system for cost advantage, then material cost is reduced, but stress corrosion resistance deteriorates and electrical conductivity decreases
Solution Approach 1:
The patent optimizes Zn content to a balanced range (3-10 wt.%) rather than high concentrations, and introduces Cr (0.1-0.8 wt.%) and Zr (0.01-0.5 wt.%) elements that form fine precipitation phases. These elements improve stress corrosion resistance and maintain electrical conductivity (≥35% IACS) while keeping material cost-effective through controlled composition.
4Reliability
If Ni element is added to generate NiSn intermetallic compounds for improving stress relaxation resistance, then stress relaxation resistance is improved, but the interaction among Ni, Sn and P elements is not considered leading to insufficient performance
Solution Approach 1:
The patent creates a multi-phase composite structure with Cu matrix, Ni-Sn intermetallic compounds, and Ni-P, Fe-P precipitation phases. The Cr and Zr elements form additional fine precipitates that pin grain boundaries. This composite microstructure achieves superior stress relaxation resistance (rate ≤25% after 1000h at 150°C) by combining multiple strengthening and stabilization mechanisms.
Solution Approach 2:
The patent creates local regions with different phase compositions and distributions. Ni-Sn compounds provide local strength, while Ni-P and Fe-P precipitates provide local precipitation hardening. Cr and Zr phases locally pin grain boundaries. This local differentiation of functions achieves comprehensive performance improvement.
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 yield strength of ≥550 MPa, electrical conductivity of ≥35% IACS, and stress relaxation rate of ≤25% after 1000 hours at 150°C, with improved bending workability and cost-effectiveness.
Implementation Method 1
the copper alloy comprises NiSi phase and Cr3Si phase, wherein a size of the NiSi phase is ≤30nm, and a size of the Cr3Si phase is 40-100nm
Implementation Method 2
a strip made of the copper alloy has a yield strength of ≥550 MPa, an electrical conductivity of ≥35% IACS%
Implementation Method 3
a stress relaxation rate of no more than 25% after being kept at 150° C for 1000 hours
Data Source
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AI summary
Disclosed in the present invention are a copper alloy and a preparation method therefor. The copper alloy comprises the following components in percentages by weight: Cu: 85-92 wt.%, Ni: 0.5-1.5 wt.%, Si: 0.2-0.8 wt.%, Sn: 0.05-0.15 wt.%, Cr: 0.1-0.8 wt.%, Zr: 0.01-0.5 wt.%, Mg: 0.01-0.3 wt.% and the balance of Zn. In a Cu-Zn-Sn alloy system, elements such as Ni, Si, Cr and Zr are added thereto in the present invention, such that the aim of composite precipitation strengthening is achieved. In addition, the present invention controls the precipitation sequence and the precipitation phase size of Ni, Cr, Zr and Si by utilizing the composite precipitation strengthening, such that the material obtains good bending characteristics and stress relaxation resistance.