Microstructures and tensile properties of 304 steel with dual nanocrystalline and microcrystalline austenite content prepared by aluminothermic reaction casting

• Published in: Philosophical magazine letters 2014-08, Vol.94 (8), p.478-486
• Main Authors: La, Peiqing, Wei, Fuan, Lu, Xuefeng, Shi, Ting, Chu, Chenggang, Wei, Yupeng, Wang, Hongding
• Format: Article
• Language: English
• Subjects: 304 stainless steel; aluminothermic reaction; Annealing; Casting; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deformation and plasticity (including yield, ductility, and superplasticity); dual nanocrystalline-microcrystalline austenite; Elasticity and anelasticity; EPMA; Exact sciences and technology; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Microscopy; Microstructure; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics; SEM; Stainless steel; TEM; tensile properties; Tensile strength; Treatment of materials and its effects on microstructure and properties; XRD
• ISSN: 0950-0839; 1362-3036
• DOI: 10.1080/09500839.2014.932456

The microstructures of 304 stainless steels with different amounts of nanocrystalline and microcrystalline austenite prepared by an aluminothermic reaction casting, without and with annealing at 1073 K for 8 h, have been investigated by X-ray diffraction, an electron probe micro-analyser, a transmission electron microscope and a scanning electron microscope. The steels, both without and with annealing, consisted of different dual nanocrystalline and microcrystalline austenite combinations and a little nanocrystalline δ ferrite, while the average grain size of the nanocrystalline austenite increased from 19 to 26 nm and volume fraction of the microcrystalline austenite increased from 17 to 30% after annealing. The tensile strength of the steel was dramatically increased from 500 to 1000 MPa and the tensile elongation ratio increased from 8 to 12% after annealing. However, the tensile strength was decreased to 600 MPa and the tensile elongation ratio increased from 12 to 22% after an annealing at 1273 K. The combination of dual nanocrystalline and microcrystalline austenite obtained after the annealing at 1073 K results in the best tensile properties.