Effects of Initial Austenite Grain Size on Microstructure and Mechanical Properties of 5% Nickel Cryogenic Steel

In the present study, the relationship between initial austenite grain size and mechanical properties of a 5% nickel cryogenic steel was investigated. The microstructures of initial austenite grains and tempered martensites were analyzed by an optical microscope. In addition, a transmission electron...

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Published inMetallography, microstructure, and analysis Vol. 8; no. 2; pp. 241 - 248
Main Authors Xiong, Tao, Xu, Guang, Yuan, Qing, Hu, Hai-jiang, Tian, Jun-yu
Format Journal Article
LanguageEnglish
Published New York Springer US 15.04.2019
Springer Nature B.V
Subjects
Austenite
Characterization and Evaluation of Materials
Chemistry and Materials Science
Grain size
Impact strength
Impact tests
Materials Science
Mechanical properties
Metallic Materials
Morphology
Nanotechnology
Nickel
Structural Materials
Surfaces and Interfaces
Technical Article
Tempered martensite
Thin Films
Toughness
Austenite grain size
Reversed austenite
Austenitizing temperature
Impact toughness
Tempered martensite
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Summary:In the present study, the relationship between initial austenite grain size and mechanical properties of a 5% nickel cryogenic steel was investigated. The microstructures of initial austenite grains and tempered martensites were analyzed by an optical microscope. In addition, a transmission electron microscope was employed to examine the morphologies of reversed austenite and refined tempered martensite laths. Further, tensile and cryogenic impact tests were conducted to evaluate the mechanical properties of the experimental steel. It was found that the impact toughness of the sample steel increased as the size of initial austenite grain decreased and the thicknesses of martensite laths decreased with the decrease in initial austenite grain size. The average grain size of initial austenite in the specimen austenitized at 830 °C for 60 min followed by tempering at 600 °C for 60 min was found to be 19.2 μm, and the maximum value of impact toughness reached 292.5 J. Therefore, the improvement in impact toughness can be attributed to the existence of refined tempered martensite laths and more amount of reversed austenites in the specimen.
ISSN:2192-9262
2192-9270
DOI:10.1007/s13632-019-00523-6