Sergio Neves Monteiro

Athermal and temperature dependent behavior of serrated flow in an austenitic stainless steel

Abstract It has been shown that the occurrence of serrated flow during the high temperature tensile deformation of an austenitic stainless steel takes place over distinct temperature ranges, these depending on strain rate. The initiation of lower temperature serrated flow appears to correlate with vacancy diffusion, while its termination is thermal. The beginning of the high temperature serrated flow may be related to the diffusion of carbon or nitrogen, while its cessation is apparently related to chromium diffusion.

On cell structure and subgrain formation in type 304 stainless steel

Abstract The formation of subgrains in Type 304 stainless steel, deformed by warm working in tension, was investigated using transmission electron microscopy. The subgrains evolved from an arrangement of dislocation cells formed during the early stages of plastic deformation. Subgrain formation is considered to be a consequence of the recovery mechanisms taking place during Stage III plastic deformation, which is the main part of the stress-strain curves for such steels above 550°C.

Effects of Carbon and Nitrogen Levels on the Temperature Ranges for Serrated Flow in Austenitic Stainless Steel

ABSTRACT The ranges of occurrence of serrated flow as a function of temperature and strain rate are reported for two type 304 stainless steels having different carbon and nitrogen contents. Analysis indicates that the low temperature serrations are controlled by diffusion of C or N; their athermal termination depends on exhaustion of available interstitials. The higher temperature serrations depend on locking of dislocations by C-C pairs with interaction with Cr, while their termination is believed to relate to carbide formation.

Aging and mechanical behavior of type 304/347 welded joints☆

Abstract Metallographic studies are reported of precipitation effects in type 304 stainless steel joined using type 347 weld metal and aged at 600 and 700°C. The changes in microhardness across the welded joint during aging and the relative resistance to fracture of the weld and base metal have been determined. The results obtained indicate that the weld metal becomes stronger than the base metal at long aging times and that tensile fracture occurs in the base metal of such specimens.

Auger Analysis of the High Temperature Embrittlement of an Alpha Brass

Auger electron spectroscopy analysis on a leaded high zinc alpha brass specimen, tensile deformed at the ductility minimum temperature, has been performed to study the possible embrittlement mechanism. It was found that a lead rich layer is formed at the grain boundaries weakening the atomic bonds and promoting intergranular fracture.