MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effect of Age-Hardening to Metal Structure and Tribology Characteristics of Lead-Free Bismuth Bronze Casting Containing Sulfur
Katsuyuki FunakiKaname FujiiShigeki TakagoToshimitu OkaneTakeshi KobayashiTakafumi Akashi
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2017 Volume 58 Issue 11 Pages 1555-1561

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Abstract

The age-hardening behavior and low friction characteristics of Cu-Sn-Bi alloy with 1.5 mass% nickel and 0.3 mass% sulfur (PBX alloy) have been investigated. The PBX alloy showed age-hardening when aged at the temperature range of 623 K to 743 K for over 0.6 ks after solution treatment at α+γ stable temperature. Peak hardness was obtained by aging at 673 K. After aging at the temperature range of 573 K to 743 K, the supersaturated solid solution part changed into eutectoid structure in which fine δ precipitated. The age-hardening of the PBX alloy showed a two-step hardening. The first step began within 0.6 ks and then hardness increased slowly with aging time. Aged at 673 K, the eutectoid matrix changed into a pine needle-shaped structure. The structure is a mixed structure of a bainitic structure and quasi-martensite having mid-rib structures in several places. Aged at 743 K, the macro crystal grain size did not change in 3.6 ks, but aging over 14.4 ks caused macro crystal grain refinement. The dynamic friction coefficient of the PBX alloy in an oil bath of 333 K was smaller than that of JIS CAC603 alloy due to the eutectoid structure of the α phase and fine δ phase.

 

This Paper was Originally Published in Japanese in J. JFS. 87 (2015) 861–867.

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© 2017 Japan Foundry Engineering Society
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