Multiphase microstructure formation and its effect on fracture behavior of medium carbon high silicon high strength steel  

作　　者：Kui Chen Huabing Li Zhouhua Jiang Fubin Liu Congpeng Kang Xiaodong Ma Baojun Zhao 

机构地区：[1]School of Metallurgy,Northeastern University,Shenyang 110819,China [2]State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang 110819,China [3]School of Chemical Engineering,The University of Queensland,Brisbane 4072,Australia

出　　处：《Journal of Materials Science & Technology》2021年第13期81-92,共12页材料科学技术（英文版）

基　　金：financially supported by the National Key Research and Development Program of China(No.2016YFB0300105);the Fundamental Research Funds for the Central Universities(No.N180725021);the Fundamental Research Funds for the Central Universities(No.N2024005-4)。

摘　　要：This work investigated the evolution of multiphase microstructure and impact fracture behavior of medium carbon high silicon high strength steel subjected to the austempering treatment at 240,360,and400℃.The results show that martensite,bainite,and retained austenite(RA)are the main microstructural phases.The austempering treatments at 360 and 400℃ caused the formation of carbon-poor ferrite in the matrix,and the transformation of ultrafine bainite into coarse lath bainite and granular bainite,respectively.Thick filmy RA was distributed between bainite laths.The polygonal martensiteaustenite islands and blocky RA formed along the grain boundaries.The average carbon concentration in the matrix decreased with the temperature increase,while the impact toughness initially increased and then dropped with temperature.The quasi-cleavage brittle fracture dominated the impact fracture mechanism of the sample austempered at 240℃ by forming tearing surfaces and tearing steps.The microcracks disappeared in the RA on the prior austenite grain boundaries.On the other side,the fracture surface of the sample austempered at 360℃ exhibited ductile fracture with deep dimples and brittle fracture with cleavage river patterns.The polygonal martensite-austenite islands or blocky RA constrained the microcracks.After austempered at 400℃,the brittle fracture was dominant,showing river patterns,and the microcracks propagated through the granular bainite without any resistance.

关 键 词：Medium carbon high silicon steel AUSTEMPERING Martensite BAINITE Retained austenite MICROCRACKS 

分 类 号：TG142.1[一般工业技术—材料科学与工程]