Directional solidification studies in Ni-Al alloys

Thesis/Dissertation · Sat May 01 04:00:00 EDT 1993

DOI:https://doi.org/10.2172/10116325· OSTI ID:10116325

Lee, Je-hyun ^[1]

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1. Iowa State Univ., Ames, IA (United States)

Three solid phases are involved in the phase equilibria of the intermetallic compound Ni₃Al near its melting point, β, γ'(Ni₃Al), and γ. The generally-accepted phase diagram involves a eutectic reaction between β' and γ, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the β and γ' phases. The phase equilibria near Ni₃Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures tonned at the solidification front, and using diffusion couple experiments. These experiments show that eutectic forms between β and γ' phases, as in the Schramm diagram. Growth and phase transformations of these three phases are also studied in the directional solidification experiments. Microstructure analysis shows that etching of Ni₃Al(γ') is very sensitive to small composition variations and crystallographic orientation changes. The eutectic solidification study confirms that the equilibrium eutectic is γ'+β, and that the metastable γ+β eutectic might be also produced in this system according to the impurities, solidification rates, and composition variations.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 10116325
• Report Number(s): IS-T--1653; ON: DE94005562
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102
ALUMINIUM ALLOYS
EUTECTICS
INTERMETALLIC COMPOUNDS
METASTABLE STATES
NICKEL BASE ALLOYS
PHASE STUDIES
SOLIDIFICATION
STRUCTURE AND PHASE STUDIES