Microstructural development in PWA-1480 electron beam welds: An atom probe field ion microscopy study

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:195779

David, S A; Miller, M K ^[1]; Babu, S S ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. The Pennsylvania State Univ., State College, PA (United States)

The microstructure development in PWA-1480 superalloy electron beam weld (Ni-11.0 at. % Al-11.5% Cr-1.9% Ti-5.1% Co-4.0% Ta-1.3% W) was characterized. Optical microscopy revealed a branched dendritic structure in the weld metal. Transmission electron microscopy of these welds, in the as-welded condition, showed fine cuboidal (0.05--0.5 {mu}m) L1{sub 2}-ordered {gamma}{prime} precipitates within the y grains. The average volume percentage of {gamma}{prime} precipitates was found to be {approx}5%. Atom probe analyses revealed that the composition of {gamma} matrix was Ni-4.6 at. % Al-25.5% Cr-0.4% Ti-9.4% Co-0.8% Ta-2.9% W and that of {gamma}{prime} precipitates was Ni-17.3 at. % Al-2.6% Cr-2.4% Ti-3.0% Co-7.4% Ta-1.3% W. These compositions were compared with the previous APFIM analyses of commercial PWA-1480 single crystals that had received conventional heat treatments. Small differences were found in the chromium and aluminum levels and these may be due to the nonequilibrium nature of phase transformations that occur during weld cooling. No solute segregation was detected at the {gamma}-{gamma}{prime}interface. The APFIM results were also compared with the thermodynamic calculations of alloying element partitioning between {gamma} and {gamma}{prime} using the ThermoCalc{trademark} software.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 195779
• Report Number(s): CONF-950808--1; ON: DE96004385
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ELECTRON BEAM WELDING
HEAT RESISTING ALLOYS
ION MICROSCOPY
MICROSTRUCTURE
T CODES
THERMODYNAMICS