High-temperature ductility of AISI 310 austenitic stainless steels

Abstract

The effects of deformation temperature and additions of impurity elements on the ductility of solution–treated 25Cr–20Ni steels have been examined at the relatively high strain rate of 0·11 ^s−1 by means of hot tensile tests. The ductility v. temperature curve can be divided into three regions: region I, 1000–1200 K, where there is a ductility minimum due to M₂₃C₆ precipitation on grain boundaries; region II, 1225–1400 K, which exhibits a plateau or a slight trough of ductility with corrugated boundaries as a result of dynamic recrystallization localized near the boundaries; and region III, 1450–1600 K, where recrystallization through the whole specimen leads to ductile fracture with complete necking. It was also confirmed that the grain boundary segregation of Sb and S and the sulphide precipitation on the grain boundaries accelerate intergranular cracking and reduce ductility in the range 1075–1300 K, and that, because sulphide particles melt on boundaries, the zero ductility temperature is markedly lowered by the addition of impurities such as S, P, or Sb.

MST/364