SYMPOSIA PAPER Published: 01 January 1979

Influence of Microstructure on the Mechanical Properties and Localized Corrosion of a Duplex Stainless Steel


The alloy studied, U50, is a ferritic-austenitic duplex stainless steel. In addition to the two major phases (that is, ferrite and austenite), several additional phases form during low and intermediate temperature aging, namely, M7C3, M23C6, σ, χ, R, γ2, and α′. This study details the precipitation of these phases and their influence on the mechanical and localized corrosion properties. The sigma phase has the most deleterious influence on the impact properties. The α′ produces the largest increase in the yield and ultimate tensile strength. The precipitation of M23C6 and σ adversely affects the pitting resistance of U50 in 0.1NHC1 because of the accompanying chromium and molybdenum depletion of the matrix. The formation of α′ also severely reduces the chromium content of the ferrite phase and thereby inhibits its passivation. The large volume percent of ferrite in the alloy prevents intergranular corrosion that typically accompanies grain boundary precipitation of M23C6 in single-phase stainless steels.

Author Information

Solomon, HD
General Electric Corporate Research and Development Center, Schenectady, N. Y.
Devine, TM
General Electric Corporate Research and Development Center, Schenectady, N. Y.
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Developed by Committee: E04
Pages: 430–461
DOI: 10.1520/STP36883S
ISBN-EB: 978-0-8031-4742-3
ISBN-13: 978-0-8031-0517-1