Microstructure and mechanical properties of an oxide-dispersed ultrafine-grained maraging steel
Bowen Shi (Northeastern University, Chinese Academy of Sciences)
Tianyi Zeng (Hunan University of Technology)
Nairong Tao (Chinese Academy of Sciences)
Xianbo Shi (Chinese Academy of Sciences)
Jiarong Zhang (Chinese Academy of Sciences)
Wei Wang (Chinese Academy of Sciences)
Sybrand van der Zwaag (TU Delft - Aerospace Engineering)
Yiyin Shan (Chinese Academy of Sciences)
Wei Yan (Chinese Academy of Sciences)
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Abstract
A novel oxide-dispersed strengthened T250 maraging steel (ODS-T250 steel) was prepared by mechanical ball milling followed by hot isostatic pressing. Martensitic transformation behavior, ultrafine-grained martensite microstructure and tensile properties of the ODS-T250 steel were compared to its oxide-free counterpart (T250 steel). The results indicated that ODS-T250 steel exhibited excellent microstructural thermal stability, maintaining an effective grain size of 0.348 μm even after quenching from 1200 °C, whereas T250 steel exhibited a much larger grain size of 5.473 μm. After quenching, the ODS-T250 steel showed significantly distinct variant selectivity, and its martensite morphology was unprecedented equiaxed structure rather than typical lath-type. Statistical analysis revealed that there was only a single variant formed when the prior austenite grain size (PAGS) was below 0.43 μm. Moreover, the martensite start (Ms) temperature of ODS-T250 steel was lower than the T250 steel due to its ultrafine PAGS and the dispersed oxide particles. The refinement of PAGS and the presence of oxide particles led to a simultaneous improvement in both strength and ductility of ODS-T250 steel.
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