The effect of phase fraction, size and shape on the dezincification of duplex brasses. (15th May 2021)

• Record Type: Journal Article
• Authors: Moriarty, Michael; Wu, Yuxiang; Murray, Timothy; Hutchinson, Christopher
• Is Part Of: Corrosion science. Volume 184(2021)
• Publication Date: 2021-05-15
• Subjects: Duplex brass -- Dezincification -- Microstructure engineering -- Percolation; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2021.109366
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Dezincification resistance of duplex brass can be strongly affected by controlling phase fraction, size and shape. The effect of FCC grain size is shown to be at least as strong as the effect of phase fraction on dezincification resistance. Acicular FCC phase shape is shown to more effectively limit dezincification resistance compared to equiaxed FCC grain shape. Microstructure control provides the brass metallurgists with new degrees of freedom to control dezincification behavior. Abstract: Duplex brass (α + β') can be susceptible to dezincification in potable water environments. The use of dezincification inhibitors is a common approach to protect the α phase, and heat treatments are usually applied to reduce the volume fraction of the susceptible β' phase. In this work, we explore an alternative 'microstructural engineering' approach to improve the dezincification resistance. A systematic study of the dezincification behaviour has been conducted on low-Pb duplex brass as a function of β' phase fraction, and α grain size and shape. Microstructures have been designed that allow deconvolution of the phase fraction, size and shape effects on dezincification. The classic expectation that less β' phase fraction improves dezincification resistance is reproduced, but it is also shown that a small α grain size with high aspect ratio (Widmanstätten α) can be just as important as the β' phase fraction for dezincification control. The dezincification behaviour has been rationalised using percolation simulations, where the β' phase interconnectivity and geometric arrangements are highlighted. These observations provide new degrees of freedom for the brass metallurgist to design microstructures that balance the required dezincification performance with the other important properties such as strength, formability, machinability and thermo-mechanical processing schedules.