Probing long-range ordering in nickel-base alloys with proton irradiation. (1st September 2018)

• Record Type: Journal Article
• Authors: Song, Miao; Yang, Ying; Wang, Mi; Kuang, Wenjun; Lear, Calvin R.; Was, Gary S.
• Is Part Of: Acta materialia. Volume 156(2018)
• Page Start: 446
• Page End: 462
• Publication Date: 2018-09-01
• Subjects: Long-range ordering (LRO) -- Ni2Cr -- Precipitation -- Irradiation effect -- Proton irradiation -- Nickel-base alloy; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.06.043
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Twelve commercial-grade austenitic alloys based on the Ni-Cr-Mo-Fe quaternary system were irradiated using 2 MeV protons at 360 °C to a damage level of 2.5 displacements per atom (dpa). Long-range ordered (Pt2 Mo-type) precipitation under proton irradiation was observed, for the first time, in alloys C22, 625, 625P, 625D, 725, and 690. No relevant short-range ordering was observed. These irradiation-enhanced long-range ordered precipitates are coherent with the matrix despite their irregular shape. Of the potential influences on long-range ordering (Ni:Cr, and Ni:(Cr + Mo) ratios, Mo, and iron concentration), Fe content was the strongest by far. The volume fraction of LRO decreases with increasing Fe content by virtue of its role as a stabilizer of the disordered FCC phase, thus reducing the energy savings from ordering. The observed effects of Fe on long-range ordering show qualitative agreement with predictions from thermodynamic modeling. Although solid state diffusion kinetics dominate long-range ordering under purely thermal conditions, ordering under irradiation here (∼ 2.5dpa) is controlled by the thermodynamic driving force. Proton irradiation thus offers a unique approach for studying the low temperature phase transformation in a thermodynamically favored, but kinetically constrained condition. Graphical abstract: Image 1