谢昂 陈胜虎 姜海昌 戎利建. Nb含量和均质化处理对奥氏体不锈钢铸态组织和力学性能的影响[J]. 金属学报, 10.11900/0412.1961.2023.00249.

摘要 相关文章 Metrics 全文: PDF(2246 KB)   摘要: 奥氏体不锈钢中添加Nb会造成铸态组织中出现大尺寸初生NbC，不利于后续二次NbC的析出控制，是制约含Nb奥氏体不锈钢发展的重要因素。本工作采用OM、SEM、TEM和单轴拉伸等研究了Nb含量和均质化处理对奥氏体不锈钢铸态组织和力学性能的影响。结果表明，Nb含量的变化改变了晶界初生NbC和M23C6碳化物的析出行为，未添加Nb的合金在晶界处析出了连续分布的M23C6碳化物；Nb含量为0.30%时，形成了初生NbC +奥氏体的共晶组织，但晶界仍析出M23C6碳化物；Nb含量进一步提高到0.90%可完全抑制M23C6析出，但共晶组织数量显著增加。随着Nb含量增加到0.90%，合金的屈服强度提高，这是由于M23C6析出被抑制而使Cr元素固溶强化、Nb的固溶强化、晶粒细化带来的细晶强化以及二次NbC的沉淀强化作用提高。然而，初生NbC与奥氏体间较差的变形协调性易诱发微裂纹的萌生，裂纹沿网状分布的NbC快速扩展而造成了沟壑状的脆性断裂，显著降低了延伸率。1250℃均质化处理后，初生NbC由长棒状转变为球状或椭球状，提高了NbC与奥氏体界面处微裂纹形成所需的临界应力，抑制了微裂纹的萌生；同时初生NbC由网状分布转变为断续分布，避免了微裂纹沿初生NbC的扩展，在基本不影响奥氏体不锈钢强度的基础上，大幅度提高了延伸率。 关键词 ： 奥氏体不锈钢,  Nb含量,  均质化处理,  碳化物析出,  力学性能     Abstract：The corrosion and mechanical properties of austenitic stainless steels can be enhanced considerably by adding Nb. Newly developed Nb-stabilized austenitic stainless steels, such as 347HFG, 316Nb, TP310HCb, NF709, and HT-UPS, exemplify this advancement. The required Nb content varies across these steels. Prior research has indicated that in the as-cast microstructure of these steels, coarse and unevenly distributed primary NbC often forms, adversely affecting their mechanical and corrosion properties. Furthermore, this coarse primary NbC depletes the solid solution of Nb, which is counterproductive for fine secondary NbC precipitation. Notably, modifying the morphology and size of primary NbC through hot working and heat treatment is challenging. To enhance the microstructure and mechanical properties of Nb-stabilized austenitic stainless steel, this study investigated the impact of Nb content and homogenization treatment on these steels. Using optical, scanning electron, and transmission electron microscopy techniques, we analyzed the microstructure and tensile properties of cast austenitic stainless steel. The findings reveal that varying Nb content influences the precipitation of primary NbC and M23C6 carbides. In Nb-free steel, M23C6 carbides precipitate continuously at grain boundaries. This precipitation still occurs in steel with 0.30% Nb, alongside the formation of NbC+γ eutectic structures. Increasing Nb content to 0.90% can suppress M23C6 carbide precipitation, although the eutectic structures become more prevalent. A notable enhancement in yield strength accompanies an increase in Nb content to 0.90%. This improvement is attributed to the solid solution strengthening by Cr (due to suppressed M23C6 carbides), Nb, grain boundary strengthening from refined grain sizes, and precipitation strengthening by secondary NbC. However, microcracks are easily nucleated at primary NbC/γ interface under plastic deformation, leading to rapid crack propagation along primary NbC networks and resulting in trench-like brittle fractures. This mechanism significantly reduces elongation. Post-homogenization treatment at 1250°C alters the primary NbC morphology from rod-like to spherical/ellipsoid. This change increases the critical stress required for microcrack nucleation at NbC/γ interfaces, thereby inhibiting microcrack initiation. Additionally, the primary NbC networks transform from continuous to discontinuous distributions, impeding microcrack propagation. Consequently, this treatment significantly enhances elongation without compromising strength. Key words： austenitic stainless steel    Nb content    homogenization treatment    carbide precipitation    mechanical properties 收稿日期: 2023-06-08      ZTFLH:  TG142.1   基金资助:国家自然科学基金项目;中核集团青年英才计划 服务 把本文推荐给朋友 加入引用管理器 E-mail Alert RSS 作者相关文章 谢昂 陈胜虎 姜海昌 戎利建 44.8K 链接本文: https://www.ams.org.cn/CN/Y0/V/I/0 [1] 王秀琦, 李天瑞, 刘国怀, 郭瑞琪, 王昭东. 交叉包套轧制Ti-44Al-5Nb-1Mo-2V-0.2B合金的微观组织演化及力学性能[J]. 金属学报, 2024, 60(1): 95-106. [2] 郑雄, 赖玉香, 向雪梅, 陈江华. 稀土元素La对AlMgSi合金性能和微结构的影响[J]. 金属学报, 2024, 60(1): 107-116. [3] 杨俊杰, 张昌盛, 李洪佳, 谢雷, 王虹, 孙光爱. 拉伸-扭转复合加载对镍基高温合金GH4169力学性能与变形机理的影响[J]. 金属学报, 2024, 60(1): 30-42. [4] 宫声凯, 刘原, 耿粒伦, 茹毅, 赵文月, 裴延玲, 李树索. 涂层/高温合金界面行为及调控研究进展[J]. 金属学报, 2023, 59(9): 1097-1108. [5] 张雷雷, 陈晶阳, 汤鑫, 肖程波, 张明军, 杨卿. K439B铸造高温合金800℃长期时效组织与性能演变[J]. 金属学报, 2023, 59(9): 1253-1264. [6] 张健, 王莉, 谢光, 王栋, 申健, 卢玉章, 黄亚奇, 李亚微. 镍基单晶高温合金的研发进展[J]. 金属学报, 2023, 59(9): 1109-1124. [7] 郑亮, 张强, 李周, 张国庆. 增/降氧过程对高温合金粉末表面特性和合金性能的影响：粉末存储到脱气处理[J]. 金属学报, 2023, 59(9): 1265-1278. [8] 陈礼清, 李兴, 赵阳, 王帅, 冯阳. 结构功能一体化高锰减振钢研究发展概况[J]. 金属学报, 2023, 59(8): 1015-1026. [9] 李景仁, 谢东升, 张栋栋, 谢红波, 潘虎成, 任玉平, 秦高梧. 新型低合金化高强Mg-0.2Ce-0.2Ca合金挤压过程中的组织演变机理[J]. 金属学报, 2023, 59(8): 1087-1096. [10] 丁桦, 张宇, 蔡明晖, 唐正友. 奥氏体基Fe-Mn-Al-C轻质钢的研究进展[J]. 金属学报, 2023, 59(8): 1027-1041. [11] 袁江淮, 王振玉, 马冠水, 周广学, 程晓英, 汪爱英. Cr2AlC涂层相结构演变对力学性能的影响[J]. 金属学报, 2023, 59(7): 961-968. [12] 吴东江, 刘德华, 张子傲, 张逸伦, 牛方勇, 马广义. 电弧增材制造2024铝合金的微观组织与力学性能[J]. 金属学报, 2023, 59(6): 767-776. [13] 张东阳, 张钧, 李述军, 任德春, 马英杰, 杨锐. 热处理对选区激光熔化Ti55531合金多孔材料力学性能的影响[J]. 金属学报, 2023, 59(5): 647-656. [14] 刘满平, 薛周磊, 彭振, 陈昱林, 丁立鹏, 贾志宏. 后时效对超细晶6061铝合金微观结构与力学性能的影响[J]. 金属学报, 2023, 59(5): 657-667. [15] 侯娟, 代斌斌, 闵师领, 刘慧, 蒋梦蕾, 杨帆. 尺寸设计对选区激光熔化304L不锈钢显微组织与性能的影响[J]. 金属学报, 2023, 59(5): 623-635. Viewed Full text Abstract Cited   Shared      Discussed