Effects of Heat Treatment Process on Microstructure and Stress Corrosion Properties of CuZn39Pb3 Alloys
The effects of heat treatment on the microstructure of CuZn39Pb3 alloy and the susceptibility to stress corrosion cracking and dezincification corrosion in 3.5wt%NaCl solution were studied by means of optical microscope(OM),scanning electron microscope(SEM),stress corrosion tester and microhardness tester.The results show that the stress corrosion sensitivity of the alloy is mainly related to the size and proportion of the α phase,the continuity of the β phase distribution and the Pb distribution of the free state.Local corrosion is caused by large α phases and the β phases of the continuous distribution.The Pb phase tends to gather at the interface between the α phase and the β phase.The reduction of phase interface area caused by coarse α phase and continuously distributed β phase will cause the Pb phase to gather at the phase interface,reduce the interfacial adhesion and reduce the stress corrosion performance of the material.A slow strain rate tensile(SSRT)test shows that the stress corrosion performance of the annealing alloy is the worst.The fine α relatively β phases in the alloy are separated after 450℃aging,and the free state Pb distributes evenly,which have the best comprehensive mechanical properties and stress corrosion properties.The immersion test shows that the dezincification corrosion sensitivity of the annealing alloy is the highest.The dezincification corrosion sensitivity at 450℃of the aging alloy is the lowest,which is consistent with its stress corrosion performance.
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