Solidification structures of Ti-(35-58)at.%Al intermetallic compounds
- Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering
- Agency for Defense Development, Taejon (Korea, Republic of)
High purity Ti-(35--58)at.%Al alloy buttons were prepared by melting and casting in a vacuum arc furnace under Ar atmosphere. The cast microstructures of near-top surface have been studied as a function of composition using optical microscope, scanning electron microscope and transmission electron microscope. The transition compositions of primary dendrite from {beta} to {alpha} phase and from {alpha} to {gamma} phase were determined to be 49--50at.%Al and 55--56at.%Al respectively. The two peritectic compositions for {beta}+L{r_arrow}{alpha}{sub p} and for {alpha}+L{r_arrow}{gamma}{sub p} were determined to be {approximately}47at.%Al and {approximately}54at.%Al respectively. The dendrite cell size was observed to be minimum at 46--47at.%Al. The mode of solid state transformation of primary {beta} to {alpha} phase during cooling continuously varied from the massive transformation to the precipitation of Widmanstaetten {alpha} plates and of {alpha} grains as the composition increased from 35at.%Al to 49at.%Al. On the other hand, the mode of transformation of primary {alpha} (or interdendritic {alpha}) to {gamma} phase varied from the precipitation (as a lamellar structure) to the massive transformation, as the Al content increased from 44at.%Al to 55at.%Al. This variation of transformation modes could be well explained in terms of the variation of the driving force and atomic mobility as a function of composition.
- OSTI ID:
- 225119
- Report Number(s):
- CONF-950201--; ISBN 0-87339-304-X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Solidification microstructures and calculated phase equilibria in the Ti-Al-Mn system
Crystal structure of [beta]-FeSiAl[sub 5] and (Be-Fe)-BeSiFe[sub 2]Al[sub 8] phases