Sn-Based Slide Member with Abnormal Intermetallic Phases
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Solution Overview
Problem
Slide members in bearing devices face fatigue-driven crack propagation due to weak boundary strength between the Sn matrix and Sn-Sb compound phase, leading to reduced longevity.
Innovation Solution
A slide member with a Sn-based alloy bearing layer containing abnormally shaped intermetallic compound phases dispersed in the Sn matrix, where the perimeter of these phases is significantly longer than their diameter, creating a complex and intricate boundary that inhibits crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional intermetallic compound phases are used in the Sn-based white metal, then the alloy layer can be formed with standard microstructure, but the boundary portion between Sn-matrix and compound phase has weak strength leading to fatigue crack propagation
Solution Approach 1:
The invention changes the geometric parameters of the intermetallic compound phase from conventional small and equiaxed shapes to abnormally large sizes (D≥80μm) with high perimeter-to-diameter ratios (Lc/D≥350%). This parameter transformation creates an intricately contoured boundary that significantly increases crack propagation path length, thereby improving both boundary strength and fatigue resistance simultaneously
Solution Approach 2:
The invention creates a composite microstructure where the Sn matrix is reinforced with abnormally shaped intermetallic compound phases that have specific geometric characteristics. The composite structure combines the ductility of the Sn matrix with the crack-arresting capability of the intricately contoured compound phase boundaries, resolving the contradiction between boundary strength and fatigue resistance
2Reliability
If the intermetallic compound phase is made larger to create intricate boundaries, then fatigue crack propagation is inhibited, but the manufacturing precision required to control the abnormal shape increases
Solution Approach 1:
The invention specifies precise parameter ranges (D≥80μm and Lc/D≥350%) that define the abnormal shape characteristics. By establishing these quantitative parameters, the invention transforms the manufacturing challenge into a controllable process where the abnormal shape can be achieved through controlled cooling rates and composition adjustments during solidification, rather than requiring post-processing precision
Data Source
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AI summary
A slide member inhibiting propagation of fatigue cracks and thereby exhibiting extended longevity and a bearing device employing such slide member. A Slide member includes a metal back (12); and a bearing alloy layer (11) provided over the metal back and comprising a Sn-based alloy. The bearing alloy layer includes a Sn matrix, and an abnormally shaped intermetallic compound phase dispersed in the Sn matrix. The abnormally shaped intermetallic compound phase meets D≧80 µm and Lc/D≧350% when Lc represents a perimeter of the abnormally shaped intermetallic compound phase within a cross section of the bearing alloy layer and D represents a diameter of a circumscribing circle of the abnormally shaped intermetallic compound phase within the cross section of the bearing alloy layer.