{"title":"The Role of Al/Ti in Precipitate-Strengthened and Austenite-Toughened Co-Free Maraging Stainless Steel.","authors":"Qihan Meng, Shuai Tian, Zhenbao Liu, Xiaohui Wang, Wenyu Zhao, Changjun Wang, Yongqing Sun, Jianxiong Liang, Zhiyong Yang, Jinli Xie","doi":"10.3390/ma17215337","DOIUrl":null,"url":null,"abstract":"<p><p>The strength of ultra-low carbon maraging stainless steels can be significantly enhanced by precipitating nanoscale intermetallic secondary phases. Retained or reversed austenite in the steel can improve its toughness, which is key to achieving an ideal combination of strength and toughness. Ti and Al are often used as cost-effective strengthening elements in maraging stainless steels but the synergistic toughening and strengthening mechanisms of Ti and Al have not been studied. To investigate the synergistic toughening and strengthening mechanisms of Ti and Al in Co-free maraging stainless steels, this paper focuses on the microstructure and mechanical properties of three alloys: Fe-12Cr-11Ni-1.7Al-0.5Ti (Steel A), Fe-12Cr-11Ni-0.5Ti (Steel B), and Fe-12Cr-11Ni-1.7Al (Steel C). The impact of Ti and Al on the microstructure and mechanical properties was investigated using X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and thermodynamic simulations. The relationship between microstructure, strength, and toughness is also discussed. The results indicated that Steel A, containing both Al and Ti, exhibited the highest strength level after solution treatment at 900 °C, with an ultimate tensile strength reaching 1571 MPa after aging at 540 °C. This is attributed to the simultaneous precipitation of spherical β-NiAl and rod-shaped η-Ni<sub>3</sub>Ti phases. Steel B, with only Ti, formed a significant amount of Ni-rich reversed austenite during aging, reducing its ultimate tensile strength to 1096 MPa. Steel C, with only Al, showed a high strength-toughness combination, which was achieved by forming dispersive nano-sized intermetallic precipitates of β-NiAl in the martensitic matrix with a slight amount of austenite. It is highlighted that Al has superior toughening and strengthening effects compared to Ti in the alloy system.</p>","PeriodicalId":18281,"journal":{"name":"Materials","volume":"17 21","pages":""},"PeriodicalIF":3.1000,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11547407/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Materials","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.3390/ma17215337","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
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Abstract
The strength of ultra-low carbon maraging stainless steels can be significantly enhanced by precipitating nanoscale intermetallic secondary phases. Retained or reversed austenite in the steel can improve its toughness, which is key to achieving an ideal combination of strength and toughness. Ti and Al are often used as cost-effective strengthening elements in maraging stainless steels but the synergistic toughening and strengthening mechanisms of Ti and Al have not been studied. To investigate the synergistic toughening and strengthening mechanisms of Ti and Al in Co-free maraging stainless steels, this paper focuses on the microstructure and mechanical properties of three alloys: Fe-12Cr-11Ni-1.7Al-0.5Ti (Steel A), Fe-12Cr-11Ni-0.5Ti (Steel B), and Fe-12Cr-11Ni-1.7Al (Steel C). The impact of Ti and Al on the microstructure and mechanical properties was investigated using X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and thermodynamic simulations. The relationship between microstructure, strength, and toughness is also discussed. The results indicated that Steel A, containing both Al and Ti, exhibited the highest strength level after solution treatment at 900 °C, with an ultimate tensile strength reaching 1571 MPa after aging at 540 °C. This is attributed to the simultaneous precipitation of spherical β-NiAl and rod-shaped η-Ni3Ti phases. Steel B, with only Ti, formed a significant amount of Ni-rich reversed austenite during aging, reducing its ultimate tensile strength to 1096 MPa. Steel C, with only Al, showed a high strength-toughness combination, which was achieved by forming dispersive nano-sized intermetallic precipitates of β-NiAl in the martensitic matrix with a slight amount of austenite. It is highlighted that Al has superior toughening and strengthening effects compared to Ti in the alloy system.
通过析出纳米级金属间次相，可显著提高超低碳马氏体不锈钢的强度。钢中残留或反向奥氏体可提高钢的韧性，这是实现强度和韧性理想结合的关键。钛和铝通常被用作马氏体时效不锈钢中具有成本效益的强化元素，但钛和铝的协同增韧和强化机制尚未得到研究。为了研究无钴马氏体时效不锈钢中 Ti 和 Al 的协同增韧和强化机制，本文重点研究了三种合金的微观结构和机械性能：Fe-12Cr-11Ni-1.7Al-0.5Ti（钢 A）、Fe-12Cr-11Ni-0.5Ti（钢 B）和 Fe-12Cr-11Ni-1.7Al（钢 C）。采用 X 射线衍射 (XRD)、高分辨率透射电子显微镜 (TEM) 和热力学模拟研究了钛和铝对微观结构和机械性能的影响。此外，还讨论了微观结构、强度和韧性之间的关系。结果表明，同时含有铝和钛的钢 A 在 900 ℃固溶处理后表现出最高的强度水平，在 540 ℃老化后的极限抗拉强度达到 1571 兆帕。这归因于球形的 β-NiAl 和棒状的 η-Ni3Ti 相同时析出。仅含 Ti 的钢 B 在时效过程中形成了大量富 Ni 的反向奥氏体，使其极限抗拉强度降至 1096 兆帕。仅含 Al 的钢 C 显示出较高的强度-韧性组合，这是通过在马氏体基体中形成分散的纳米级β-NiAl 金属间析出物和少量奥氏体而实现的。这突出表明，在合金体系中，Al 的增韧和强化效果优于 Ti。
期刊介绍：
Materials (ISSN 1996-1944) is an open access journal of related scientific research and technology development. It publishes reviews, regular research papers (articles) and short communications. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. Therefore, there is no restriction on the length of the papers. The full experimental details must be provided so that the results can be reproduced. Materials provides a forum for publishing papers which advance the in-depth understanding of the relationship between the structure, the properties or the functions of all kinds of materials. Chemical syntheses, chemical structures and mechanical, chemical, electronic, magnetic and optical properties and various applications will be considered.
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