摘要:

AbstractThe microstructural evolution of Mo bearing and Mo free cast duplex stainless steels, induced by long term aging in the range 350–4507deg;C has been studied using atom probe and field ion microscopy and transmission electron microscopy. The salient features of this evolution at 350 and 400°C are spinodal decomposition and G phase precipitation in the ferrite. The nucleation of the G phase is enhanced by spinodal decomposition. Other intermetallic phases observed at higher temperatures may also be formed at 400°C. In the ferrite/ austenite interface, an intermetallic film, possibly an icosahedral phase, is formed after aging for 30 000 h at 400 and 450°C in Mo bearing steels, whereas interfacial M23C6carbides precipitate in the Mo free materials. The observed evolution of the spatial and compositional parameters of the spinodal decomposition in Mo bearing steels is described and its relationship with the evolution of mechanical properties is outlined.MST/1185

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.3.301

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractType 308 stainless steel is often used as weld filler metal in light water reactor piping systems. In similar cast CF8 type steels, the ferrite phase has been shown to be responsible for the reported degradation in properties after long term aging at temperatures between 300 and 400°C. Despite the relatively low volume fraction of ferrite in the type 308 materials, long term aging at the maximum operating temperature (343°C) results in a significant loss of impact toughness. Using TEM, G phase precipitation was detected in the ferrite matrix of the aged welds both in the matrix and on dislocations. Composition modulations in the aged ferrite consistent with spinodal decomposition were detected in atom probe composition profiles. A variety of statistical techniques was used to analyse the atom probe composition profiles. The spinodal decomposition of the ferrite into iron rich and chromium enriched regions is the most likely cause of the mechanical property degradation of these materials during aging.MST/1188

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.3.314

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.3.321

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor