Mechanical properties evaluation and plastic instabilities of Fe-9%Cr ODS steels

The Fe-9%Cr oxide-dispersion-strengthened (ODS) steels were fabricated by mechanical alloying, hot isostatic pressing and subsequent different thermomechanical treatments. The microstructure of the Fe-9%Cr ODS steels was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The SEM analysis revealed that the matrixes of quenched Fe-9%Cr ODS steel and tempered Fe-9%Cr ODS steel are martensitic and ferritic, respectively. Large-sized particles can be found distributed along the grain boundaries by SEM analysis, while the TEM analysis showed that a large number of fine nano-sized Y-Ti-O particles distributed in the grains. The room-temperature tensile properties of Fe-9%Cr ODS steels treated at different conditions were measured and the uniform elongations (UEs) were evaluated. The UEs of the researched ODS steels are less than 10% probably due to the decohesion phenomenon caused by the large-sized (200–500 nm) particles distributed along the grain boundaries. Furthermore, Charpy impact tests were done to investigate the impact properties of the tempered Fe-9%Cr ODS steel from −180°C to 200°C. The ductile-brittle transition temperature (DBTT) of tempered Fe-9%Cr ODS steel is about −60°C as judged by the energy-temperature curve. These results are important for the mechanical processing and component fabrication of ODS steels.