高温低周疲劳下C-HRA-5奥氏体耐热钢中孪晶界演变  

Twin Boundary Evolution Under Low-Cycle Fatigue ofC-HRA-5 Austenitic Heat-Resistant Steel atHigh Temperature

作　　者：周红伟 高建兵[2] 沈加明 赵伟 白凤梅 何宜柱 ZHOU Hongwei;GAO Jianbing;SHEN Jiaming;ZHAOWei;BAI Fengmei;HE Yizhu(Key Laboratory of Green Preparation and Surface Technology of Advanced Metal Materials,Ministry of Education,School of Materials Science and Engineering,Anhui University of Technology,Ma’anshan 243032,China;State Key Laboratory of Advanced Stainless Steel Materials,Taiyuan Iron and Steel(Group)Co.,Ltd.,Taiyuan 030003,China;Anhui Key Laboratory of Metallurgical Engineering and Comprehensive Utilization of Resources,School of Metallergical Engineering,Anhui University of Technology,Ma’anshan 243032,China)

机构地区：[1]安徽工业大学材料科学与工程学院先进金属材料绿色制备与表面技术教育部重点实验室,马鞍山243032 [2]太原钢铁(集团)有限公司先进不锈钢材料国家重点实验室,太原030003 [3]安徽工业大学冶金工程学院冶金工程与资源综合利用安徽省重点实验室,马鞍山243032

出　　处：《金属学报》2022年第8期1013-1023,共11页Acta Metallurgica Sinica

基　　金：安徽省自然科学基金项目No.2008085ME127;安徽省高等学校自然科学研究重点项目No.KJ2020A0252;山西省重大科技攻关项目No.20181101014。

摘　　要：研究了先进超超临界燃煤机组用新型奥氏体耐热钢C-HRA-5在700℃低周疲劳下退孪生行为,利用SEM、EBSD和TEM等对孪晶界(TBs)的演变、退孪生机制及残留TBs对疲劳裂纹的影响进行了分析。结果表明,C-HRA-5钢经高温固溶处理后,低Σ重合位置点阵(CSL)晶界比例达到69%,以Σ3型TBs为主。在高温低周疲劳下,出现了显著的退孪生现象,且退孪生程度随着应变幅的增加而增加。退孪生机制主要与位错-TBs交互作用和TBs上相析出有关。疲劳试样中塑性变形以平面滑移为主,形成了大量的位错滑移带结构。位错滑移带循环碰撞TBs,导致晶界共格关系消失并最终退孪生。位错-TBs交互作用诱导部分TBs析出M_(23)C_(6)相,析出相加剧TBs对位错的钉扎作用,强化位错-TBs的交互作用,加速退孪生过程。与C-HRA-5钢中随机晶界相比,残留TBs仍然具有较高的强度,抑制疲劳裂纹的萌生与扩展。C-HRA-5 steel is a new type of austenitic heat-resistant steel with excellent oxidation resistance and corrosion resistance,and high endurance strength at high temperatures.This steel can be used in superheaters and reheaters applied in 630-700oC advanced ultrasupercritical fossil-fired power plants,which is of great strategic significance to realize national energy savings and emission reduction targets.Detwinning often occurs in austenitic stainless steel when high-temperature fatigue and creep set in.However,the detwinning mechanism in C-HRA-5 steel during high-temperature fatigue and its influence on fatigue crack initiation and propagation remain unclear.Therefore,in this work,the detwinning behavior of C-HRA-5 steel under strain-controlled low-cycle fatigue(LCF)was studied at 700oC.The evolution of twin boundaries(TBs),detwinning mechanism,and influence of residual TBs on fatigue cracks were analyzed using SEM,EBSD,and TEM.After solution treatment at high temperatures,the fraction of low coincidence site lattice boundaries reached 69%in C-HRA-5 steel with dominantΣ3-type TBs.There was a remarkable detwinning effect under LCF loading.The degree of detwinning increased with increasing strain amplitude ranging from 0.3%to 0.7%.The detwinning mechanism was mainly related to the interactions at the dislocation TBs and precipitation of M_(23)C_(6) at TBs.The plastic deformation of C-HRA-5 steel was dominated by planar slip under LCF loading,which resulted in dislocation gliding on particular planes.Therefore,numerous dislocation slip bands were formed.The collision of dislocation slip bands with TBs changed the coherent orientation of TBs and eventually led to detwinning.Meanwhile,the dislocation-TBs interaction induced the precipitation of M_(23)C_(6) carbide at some TBs during LCF at 700oC,which strengthened the pinning of TBs on dislocations,thus accelerating the detwinning process.The residual TBs had higher strength than random grain boundaries and could inhibit the initiation and propagation of fatigue cra

关 键 词：奥氏体耐热钢 低周疲劳 退孪生 EBSD 疲劳裂纹 

分 类 号：TG142.73[一般工业技术—材料科学与工程]