Roles of nanoscale precipitates and metastable austenite in determining strength and toughness of high-strength Nb-bearing steel
作者机构：State Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang110819LiaoningChina
出 版 物：《Journal of Iron and Steel Research(International)》 (钢铁研究学报（英文版）)
年 卷 期：2022年第29卷第10期
页 面：1646-1658页
核心收录：
学科分类：08[工学] 0806[工学-冶金工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学]
基 金：The authors gratefully acknowledge financial support by the National Key R&D Program of China(Grant No.2017YFB0305300) the Joint Fund project of the Ministry of Education for Equipment Pre-research(6141A020222).
主 题：High-strength structural steel Tempering Nanoscale precipitate Metastable austenite Mechanical property
摘 要：The effects of tempering temperature on the microstructure and mechanical properties of high-strength structural steel containing niobium were investigated to examine the roles of nanoscale precipitates and metastable austenite in determining the yield strength and toughness.After hot-rolling and quenching,three experimental steels were tempered at 590,630,and 670℃.During tempering,nanoscale Nb(C,N)precipitates were formed with the recovery of quenched martensite.The average diameters of Nb(C,N)precipitates increased from 5.4 to 8.2 nm as the tempering temperature was increased.Notably,reversed austenite with a volume fraction of 9%was formed at tempering temperatures up to 670℃.The yield strengths of steel containing tempered martensite tempered at 590 and 630℃ were 965 and 831 MPa,and the tensile strengths were 998 and 879 MPa,respectively.However,the steel comprising reversed austenite and tempered martensite tempered at 670℃ showed continuous yielding behavior,affording yield and tensile strengths of 610 and 889 MPa,respectively.The impact energy increased from 105 to 260 J at−60℃ with increasing tempering temperature.Reversed austenite improves low-temperature toughness by significantly increasing the crack propagation energy.
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