Tin-Phosphor Bronze Strip Grain-Boundary Control for Strength and Bending
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Solution Overview
Problem
Existing tin-phosphor bronze strips fail to achieve high mechanical strength and excellent bending formability simultaneously due to a low proportion of special grain boundaries and inadequate consideration of grain size.
Innovation Solution
A fine-grain tin-phosphor bronze alloy strip with controlled grain size (1-3 μm) and standard deviation (0.9 μm or below) and a high proportion of low-ΣCSL grain boundaries, particularly Σ3, Σ9, and Σ27, is produced through a sequence of cold rolling and heat treatment processes, including batching, continuous casting, and multiple recrystallization annealing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the proportion of special grain boundaries is increased through conventional heat treatment, then the corrosion and fracture resistance is improved, but the grain size becomes large and mechanical strength decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling heat treatment temperature (400-800°C) and time (0.5-5 h), along with deformation amount (5-40%), to simultaneously achieve fine grain size (1-3 μm) and high proportion of special grain boundaries (66-74%), resolving the contradiction between improving reliability and maintaining strength
Solution Approach 2:
The patent employs preliminary deformation (5-40%) before heat treatment to create a microstructure that will subsequently form fine grains and special grain boundaries during the controlled heat treatment process, ensuring both high strength and improved reliability
2Strength
If the grain size is reduced to improve mechanical strength, then the bending formability deteriorates due to insufficient special grain boundary proportion
Solution Approach 1:
The patent changes multiple parameters including deformation amount (5-40%), heat treatment temperature (400-800°C), and time (0.5-5 h) to achieve the optimal combination of fine grain size (1-3 μm) and high special grain boundary proportion (66-74%), simultaneously improving strength and bending formability
Solution Approach 2:
The patent creates a composite microstructure combining fine grains with high proportion of special grain boundaries (Σ3, Σ9, Σ27), where the fine grains provide strength and the special grain boundaries provide bending formability by blocking crack propagation
3Reliability
If conventional heat treatment is applied to increase special grain boundaries, then the grain boundary structure is improved, but the grain size control is insufficient
Solution Approach 1:
The patent precisely controls heat treatment parameters (temperature 400-800°C, time 0.5-5 h) and deformation parameters (amount 5-40%) to simultaneously achieve fine grain size (1-3 μm) with standard deviation ≤0.9 μm and high special grain boundary proportion (66-74%), resolving the contradiction between improving grain boundary structure and controlling grain size
Solution Approach 2:
The patent employs feedback control by measuring and analyzing the grain size distribution (standard deviation ≤0.9 μm) and special grain boundary proportion (66-74%) to optimize and adjust the heat treatment and deformation parameters, ensuring precise control of both grain size and grain boundary structure
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 fine-grain tin-phosphor bronze alloy achieves enhanced mechanical strength and bending formability by effectively hindering dislocation movement with special boundaries, maintaining a uniform grain structure and high tensile strength while retaining excellent bending performance.
Implementation Method 1
subjecting the pretreated tin-phosphor bronze alloy strip to cold rolling deformation and heat treatment steps sequentially
Implementation Method 2
subjecting the pretreated tin-phosphor bronze alloy strip to cold rolling deformation and heat treatment steps sequentially
Implementation Method 3
multiple recrystallization annealing steps
Implementation Method 4
regulate the distribution of grain boundary character distribution (GBCD) of a material through a certain thermo-mechanical process, in order to increase the proportion of low-ΣCSL grain boundary
Implementation Method 5
grain boundaries are the main obstacles for dislocation and gliding during plastic deformation, becoming an important source of strength and work hardening
Data Source
AI summary
The disclosure provides a fine-grain tin-phosphor bronze alloy strip and a preparation method thereof. The fine-grain tin-phosphor bronze alloy strip comprises the following elements in percentage by mass: 4.0-10 wt % of Sn, 0.01-0.3 wt % of P and the balance of Cu and inevitable impurity elements, the average grain size of the tin-phosphor bronze alloy strip is 1-3 μm, the grain size is in normal distribution, and the standard deviation of the grain size is 0.9 μm or below; the proportion of the total low-ΣCSL grain boundary in the tin-phosphor bronze alloy strip in the whole grain boundary is 66-74%, and in the total low-ΣCSL grain boundary, the ratio range of (Σ9+Σ27)/Σ3 is 0.12-0.23:1. The fine-grain tin-phosphor bronze alloy strip of this disclosure enables a finished strip can have the tensile strength and the excellent bending performance at the same time.