The influence of retained austenite on [alpha]-[alpha][prime] phase decomposition in Fe-Cr alloys

Journal Article · Sun May 15 00:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90263-1· OSTI ID:7199089

Horton, L L; Miller, M K ^[1]

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1. Oak Ridge National Lab., TN (United States). Metals And Ceramics Div.

It is well known that iron-chromium alloys are susceptible to phase separation within a low temperature miscibility gap and that this decomposition is deleterious to the mechanical properties of the material. This 475 [degree] embrittlement is of concern in commercial applications such as in the duplex stainless steel pipes that are used to carry the primary coolant water in nuclear power reactors. In these duplex stainless steels, the microstructure consists of austenite and 10 to 20% [delta]-ferrite. During service at a temperature of approximately 288 C, the ferrite phase of these steels undergoes spinodal decomposition and forms an iron-rich [alpha] phase and a chromium-enriched [alpha][prime] phase. Dislocations have difficulty in cutting through the complex interconnected morphology of these phases and therefore the hardness increases and the steel becomes embrittled. However, the effect of the presence of the austenite on the kinetics and morphology of the phases formed by spinodal decomposition is unclear. In this paper, the results of a combined transmission electron microscopy (TEM) and atom probe field ion microscopy (APFIM) investigation into the influence of retained austenite on the [alpha]-[alpha][prime] phase decomposition is presented. The material chosen for this investigation was a commercial Chromindur 2 magnetic material. This material has the advantages that it exhibits good contrast between the [alpha] and [alpha][prime] phases in both the transmission electron microscope and the field ion microscope and it does not have any other competing reactions such as the formation of ultrafine G-phase precipitates that occurs in some duplex stainless steels during low temperature aging.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7199089
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 30:10; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200 -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM NITRIDES
CHROMIUM STEELS
COOLING SYSTEMS
DATA
ENERGY SYSTEMS
EXPERIMENTAL DATA
HIGH ALLOY STEELS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
PHASE STUDIES
PNICTIDES
PRECIPITATION
PRIMARY COOLANT CIRCUITS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTOR MATERIALS
SEPARATION PROCESSES
STAINLESS STEELS
STEELS
TRANSITION ELEMENT COMPOUNDS