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Electron-Metallographic Identification of Retained Austenite in Steels

1975; Cambridge University Press; Volume: 33; Linguagem: Inglês

10.1017/s0424820100113779

2690-1315

B. V. Narasimha Rao, J.Y. Koo, G. Thomas,

Welding Techniques and Residual Stresses

Recently it has been discovered by electron microscopy that even in medium carbon steels (M f ≳200°C) small quantities of interlath retained austenite (γ) is present in as-quenched structures. It is speculated that this small quantity of retained γ can have a profound influence on the mechanical properties of steel. This austenite is severely deformed and in most cases the amount is so small that detection by x-ray analysis becomes impossible. However, sophisticated electron microscopic techniques involving careful selected area diffraction, bright field and dark field imaging can unequivocally establish the presence of such small quantities of austentite. Extremely useful morphological and microstructural information on the austenite can also be obtained from the electron metallography.