New type of γ′ phase in Ni based single crystal superalloys: Its formation mechanism and strengthening effect. (5th May 2018)

• Record Type: Journal Article
• Authors: Ru, Yi; Zhang, Heng; Pei, Yanling; Fu, Yongling; Li, Shusuo; Gong, Shengkai; Xu, Huibin
• Is Part Of: Materials & design. Volume 145(2018)
• Page Start: 181
• Page End: 195
• Publication Date: 2018-05-05
• Subjects: Single crystal -- Superalloy -- Precipitate -- Mechanical property -- Finite-element calculation; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2018.02.053
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: New type of γ′-precipitate in Ni-(6-8)Al-(7-12)Mo-4.5Ta-1.5Re (weight%) single-crystal superalloys and its effect on mechanical properties have been investigated. The phase exhibits a rattan form from cross-sectional observation while a curved thin film in stereoscopic structure. Its density is strongly linked to Al and Mo contents and holding time of solid solution. Its formation arises as a result of i) the overlap of γ′-precipitate and ii) the subsequent interface migration; the former is caused by the mismatch of γ-γ′ periodicity, which is inherited from the congruent ordering and spinodal decomposition independently occurring in different regions; the latter is driven from the chemical potential difference between γ-ribbon and γ′-precipitate induced by interface curvature and misfit stress. The γ′-rattan improves room temperature tensile properties through changing the slip lines and inhibiting the crack growth, which is ascribed to the change in the stress field of γ-γ′ structure. Graphical abstract: Unlabelled Image Highlights: Newly found γ′-precipitate exhibits a rattan form from cross-sectional observation while a curved thin film in stereoscopic structure. The γ′-rattan density is sensitive to the alloy composition and holding time of solid solution. Its formation arises from the overlap of γ′-precipitate caused by γ-γ′ periodicity mismatch and the subsequent interface migration. Interface migration results from the chemical potential difference between γ-ribbon and γ′-phase being linked to interface curvature and misfit-induced stress. Room temperature tensile properties enhance by γ′-rattan density, caused by the change in the two-phase stress field by γ′-rattan.