Microstructure and crystallography of unidirectionally solidified Ni-W eutectic alloy
A Ni-W eutectic alloy was subjected to a process of unidirectional solidification (UDS) by the Bridgman-Stockbarger technique. Three phases were identified by transmission electron microscopy namely: W fibers, a solid solution matrix of W in Ni, and Ni/sub 4/W precipitates of the D1a structur in the matrix. The growth axis of the W-fibers was found to be <111> and the orientation relationship between them and the Ni(N) matrix was identified as the Bain type, so that (100) /SUB bcc/ exclamationexclamation(100) /SUB fcc/ . The shape of the Ni/sub 4/W precipitates varies from equiaxial at high solidification rates to elongated plates at low rates. The orientation relationship between the precipitates and the matrix is the same for all solidification rates. The microstructure of specimens subjected to creep deformation was studied and the deformation modes were identified. These include dislocations and microtwins that originate mainly at the boundary between the Ni(W) matrix and the W-fibers. In some specimens the creep test was carried out after solution treatment at 1030 /sup 0/C followed by quenching, which resulted in a Ni(W matrix reinforced with W-fibers without Ni/sub 4/W precipitates. The microstructural changes during this creep process and the fracture surface were studied by SEM and TEM.
- Research Organization:
- Department of Materials Engineering, Technion, Israel Institute of Technology, Haifa
- OSTI ID:
- 5975289
- Journal Information:
- Metall. Trans., A; (United States), Vol. 16A:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NICKEL ALLOYS
CRYSTALLOGRAPHY
MICROSTRUCTURE
SOLIDIFICATION
TUNGSTEN ALLOYS
BRIDGMAN METHOD
CREEP
DISLOCATIONS
EUTECTICS
FIBERS
GRAIN GROWTH
GRAIN ORIENTATION
PHASE STUDIES
PRECIPITATION
QUENCHING
STOCKBARGER METHOD
TUNGSTEN
VERY HIGH TEMPERATURE
ALLOYS
CRYSTAL DEFECTS
CRYSTAL GROWTH METHODS
CRYSTAL STRUCTURE
ELEMENTS
LINE DEFECTS
MECHANICAL PROPERTIES
METALS
ORIENTATION
PHASE TRANSFORMATIONS
SEPARATION PROCESSES
TRANSITION ELEMENTS
360101* - Metals & Alloys- Preparation & Fabrication
360102 - Metals & Alloys- Structure & Phase Studies