Transformation to Ni[sub 5]Al[sub 3] in a 63. 0 at. pct Ni-Al alloy

Journal Article · Fri Jan 01 00:00:00 EST 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02669606· OSTI ID:6209600

Khadkikar, P S ^[1]; Locci, I E; Michal, G M ^[2]; Vedula, K ^[3]

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1. Therm-O-Disc, Inc., Mansfield, OH (United States)
2. Case Western Reserve Univ., Cleveland, OH (United States) NASA Lewis Research Center, Cleveland, OH (United States)
3. Iowa State Univ., Ames (United States)

Microstructures in a 63 at. pct Ni-Al alloy, produced by a powder metallurgy process, have been investigated in detail in as-quenched and aged (823 to 923 K) conditions. The parent L1[sub 0] martensite plus B[sub 2] NiAl microstructure in the as-quenched state transformed nearly completely to the orthorhombic Ni[sub 5]Al[sub 3] phase upon aging at 823 K for 720 hours. The volume fraction of Ni[sub 5]Al[sub 3] formed as a function of aging time at 823 K was observed to obey cellular reaction kinetic behavior. The specimens aged at 823 K for short times indicated that nucleation of the Ni[sub 5]Al[sub 3] phase occurred preferentially at grain boundaries. Transmission electron microscopy (TEM) observations of short-time aged specimens revealed a complex microstructure consisting of short-range ordered domains of Ni[sub 2]Al in a matrix of 7R martensite, in addition to new variants of 3R martensite and Ni[sub 5]Al[sub 3]. Aging at 873 and 923 K for 720 hours produced a stable two-phase microstructure consisting of NiAl and Ni[sub 5]Al[sub 3]. A quantitative phase analysis was carried out to calculate the (NiAl + Ni[sub 5]Al[sub 3])/Ni[sub 5]Al[sub 3] phase boundary locations. The measured lattice parameters of Ni[sub 5]Al[sub 3] formed at 823, 873, and 923 K indicated an increase in tetragonality of the phase with increasing nickel content.

• OSTI ID: 6209600
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24:1; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
MICROSTRUCTURE
PHASE TRANSFORMATIONS
NICKEL BASE ALLOYS
AGING
EXPERIMENTAL DATA
GRAIN BOUNDARIES
INTERMETALLIC COMPOUNDS
MARTENSITE
PHASE STUDIES
POWDER METALLURGY
QUENCHING
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ALLOYS
CARBON ADDITIONS
COHERENT SCATTERING
DATA
DIFFRACTION
ELECTRON MICROSCOPY
INFORMATION
IRON ALLOYS
METALLURGY
MICROSCOPY
NICKEL ALLOYS
NUMERICAL DATA
SCATTERING
TEMPERATURE RANGE
360102* - Metals & Alloys- Structure & Phase Studies