Crystallography of preferred growth in lead--tin alloys
The preferred growth of the lead--tin eutectic alloy was studied by use of electron channeling techniques in a scanning electron microscope. Four distinct crystallographic modes were found to exist depending on the imposed growth velocity. The extent of the range of the stability of each mode was experimentally determined in a directional solidification apparatus and rationalized in terms of simple physical reasoning. Microstructural observations are discussed in terms of the nature of the extent of the stability of the various crystallographic relationships. Lamellar spiraling about the growth direction was found to occur in one crystallographic mode and the parameters controlling it, growth velocity and temperature gradient, were investigated. The rate of lamellar spiraling was found to increase by increasing solidification rate or temperature gradient. The study suggests that considerably more control over the microstructural and crystallographic characteristics of a eutectic structure is possible than was previously believed. 17 figures, 34 references.
- Research Organization:
- Ames Lab., Iowa (USA); Iowa State Univ. of Science and Technology, Ames (USA)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 7185897
- Report Number(s):
- IS-T-718
- Country of Publication:
- United States
- Language:
- English
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