Phase and its morphologies of Ti-45%Al alloy directionally solidified at different growth rates
(School of Materials Science and Engineering, Harbin Institute of Technology,
Harbin 150001, China)
Harbin 150001, China)
Abstract: The microstructures of Ti-45%Al(molar fraction) alloy directionally solidified at different growth rates in alumina tube by electromagnetic heating zone melting were studied. The measured temperature gradient of the system is about 104K/m. The microstructures show that the primary solidified phase is β phase at different growth rates. The growth at low rates from 1.94×10-6m/s to 4.16×10-6m/s results in a transient solid/liquid interface structure from planar to shallow cellular. This transient rate is larger than the theoretical value of vc=6.94×10-7m/s. Compared with vt=vc/k=1.01×10-6m/s, the cellular-dendritic transient rate of experiment is observed in the range of 1.67×10-5-2.50×10-5m/s. The primary arm spacing decreases with increasing growth rate.
Key words: Ti-45Al alloy; directional solidification; growth rate; interface structure