Effect of hafnium addition on the microstructure and tensile properties of aluminum added high-Cr ODS steels

To investigate the effects of hafnium (Hf) addition on the microstructural and mechanical performance of an aluminum (Al) added 16Cr ODS steel, the microstructures of the 16Cr ODS steel with and without Hf were investigated by EBSD and TEM, and tensile tests were conducted at high temperature to evaluate the strength and ductility changes at different temperatures. The Hf addition is beneficial to the grain refinement of the 16Cr ODS steel. The average grain size decreases from 1.795 μm to 1.027 μm with Hf addition. In addition to the YAlO nanoparticles, YHfO complex oxides with a finer size are also observed in the sample with the Hf addition, which reduces the mean size of oxides within the steel and increases the number density of the oxide particles. The yield strength and tensile strength of the 16Cr ODS steel are further improved by Hf addition due to its optimized microstructures with further refined grains.