Strengthening Mechanisms in Nano Oxide Dispersion-Strengthened Fe-18Cr Ferritic Steel at Different Temperatures

Abstract

The objective of the present work is to evaluate isothermal uniaxial compressive deformation behavior of nano oxide dispersion-strengthened (n-ODS)-18Cr ferritic steel over a range of temperatures RT-1173 K and range of strain rates 10 À4 to 10 À2 s À1 . Irrespective of temperature, the influence of the strain rate on the yield strength is insignificant up to 673 K. It is found that the plot of variation of yield strength as a function of temperature exhibits three regimes, which indicates that different deformation mechanisms are governing the yield strength of n-ODS-18Cr steel. Transmission electron microscopic analysis of a sample deformed at the highest temperature of 1173 K and the lowest strain rate of 10 À4 s À1 demonstrates no significant change in the grain size and nanoprecipitate size. Also, it confirms the interaction between dislocations and nanoprecipitates. Different deformation mechanisms governing the yield strength of n-ODS-18Cr steel are identified in all three regimes and their contributions are quantified.