Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

Journal Article · Wed May 01 00:00:00 EDT 1996 · Journal of Materials Research

DOI:https://doi.org/10.1557/JMR.1996.0145· OSTI ID:284272

Seehra, M S; Babu, V S ^[1]

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1. Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

• OSTI ID: 284272
• Journal Information: Journal of Materials Research, Vol. 11, Issue 5; Other Information: PBD: May 1996
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
INCONEL 718
PHYSICAL PROPERTIES
TEMPERATURE RANGE 1000-4000 K
AGING
PHASE TRANSFORMATIONS
CRYSTAL STRUCTURE
OXIDATION
X-RAY DIFFRACTION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0-13 K
TEMPERATURE RANGE 13-65 K
TEMPERATURE RANGE 65-273 K
TEMPERATURE RANGE 273-400 K
TEMPERATURE RANGE 400-1000 K