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Incipient Melting Behavior and Its Influences on the Mechanical Properties of a Directionally Solidified Ni-Based Superalloy with High Boron Content
Zhang Hongwei1,2; Qin Xuezhi2; Li Xiaowu1; Zhou Lanzhang2
Corresponding AuthorZhou Lanzhang(lzz@imr.ac.cn)
2017-06-01
Source PublicationACTA METALLURGICA SINICA
ISSN0412-1961
Volume53Issue:6Pages:684-694
AbstractA new directionally solidified Ni-based superalloy is developed for industrial gas turbine applications, which has high strength and excellent hot corrosion resistance at high temperatures. The high strength of the alloy is primarily derived from precipitation hardening by ordered L12 gamma' phase. To achieve a uniform distribution of precipitated gamma' particles for optimized mechanical properties, the suitable heat treatments are used. However, the heat treatment temperature in Ni-based superalloys is limited by the problem of incipient melting. Incipient melting microstructrue evolution during heat treatment has been hardly reported. Therefore, the behaviors of incipient melting and its effect on mechanical properties in the new directionally solidified superalloy DZ444 with high boron have been investigated in this work. The results show that some interdendritic regions of the as-cast DZ444 sample exhibit many of gamma'/gamma eutectic, MC carbides and multi-phase eutectic-like constituent which are composed of boride, Ni5Hf and eta phases. During solution treatments, incipient melting does not occur in boride or Ni5Hf phase with low melting point firstly, but appears in gamma matrix around multi-phase eutectic-like constituent which is affected significantly by borides. Compared to DZ444 alloy with the normal boron content, incipient melting occurs at the lower temperature in the range between 1160 degrees C and 1170 degrees C. Incipient melting can occur significantly with the increase of the solid solution temperature or time. Incipient melting consists of typical gamma dentrites and a lot of tiny precipitation particles after the water quenching (WQ) method following solution treatment. However, incipient melting forms multi-phase eutectic-like constituent, gamma matrix and gamma'/gamma eutectic successively during air cooling (AC) following solution treatment, and the morphology of multi-phase eutectic-like constituent is similar to that of as-cast alloy. Firstly, a so-called incipiently melted circle (IMC) forms around multi-phase eutectic-like constituent; with the increase of the solid solution temperature or time, IMC extends inwards which makes gamma matrix and multi-phase eutectic-like constituent in this circle melt successively. Finally, a incipiently melted pool forms gradually. Incipient melting is limited to the IMC below 1200. and the area of incipient melting changes with temperature or time correspondingly. However, incipiently melted region (IMR) expands outwards continuously which makes gamma matrix outside the incipiently melted circle melt when the temperature is higher than 1210 degrees C. Especially, IMR swallows up plenty of gamma matrix, and many matrix islands, regions unmelted, exist in IMR above 1250 degrees C which destroys the continuity of the matrix significantly. The incipient melting has a minor effect on the tensile properties, nevertheless, decreases the creep-rupture properties remarkably. The degradation of mechanical properties mainly results from the increasing of the incipient melting area fraction and size.
Keyworddirectionally solidified superalloy solid solution treatment incipient melting multi-phase eutectic-like constituent mechanical property
Funding OrganizationNational Natural Science Foundation of China ; National High Technology Research and Development Program of China
DOI10.11900/0412.1961.2016.00495
Indexed BySCI
Language英语
Funding ProjectNational Natural Science Foundation of China[51001101] ; National High Technology Research and Development Program of China[2012AA03A501]
WOS Research AreaMetallurgy & Metallurgical Engineering
WOS SubjectMetallurgy & Metallurgical Engineering
WOS IDWOS:000405561500006
PublisherSCIENCE PRESS
Citation statistics
Cited Times:7[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.imr.ac.cn/handle/321006/124698
Collection中国科学院金属研究所
Corresponding AuthorZhou Lanzhang
Affiliation1.Northeastern Univ, Sch Mat Sci & Engn, Dept Mat Phys & Chem, Shenyang 110819, Peoples R China
2.Chinese Acad Sci, Inst Met Res, Shenyang 110016, Peoples R China
Recommended Citation
GB/T 7714
Zhang Hongwei,Qin Xuezhi,Li Xiaowu,et al. Incipient Melting Behavior and Its Influences on the Mechanical Properties of a Directionally Solidified Ni-Based Superalloy with High Boron Content[J]. ACTA METALLURGICA SINICA,2017,53(6):684-694.
APA Zhang Hongwei,Qin Xuezhi,Li Xiaowu,&Zhou Lanzhang.(2017).Incipient Melting Behavior and Its Influences on the Mechanical Properties of a Directionally Solidified Ni-Based Superalloy with High Boron Content.ACTA METALLURGICA SINICA,53(6),684-694.
MLA Zhang Hongwei,et al."Incipient Melting Behavior and Its Influences on the Mechanical Properties of a Directionally Solidified Ni-Based Superalloy with High Boron Content".ACTA METALLURGICA SINICA 53.6(2017):684-694.
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