Primary Solidification Phase and Lamellar Orientation in Directionally Solidified Ti-45A1-7Nb Alloy

摘要

Primary solidification phase and lamellar orientation are investigated in Ti-45A1-7Nb alloy at very high ratio of temperature gradient to growth rate (G/v) by a liquid-metal-cooled directionally solidified method.It shows that Ti-45A1-7Nb alloy solidifies with primary α phase.Longitudinal (parallel to growth direction) microstructure shows that a dendrites in solid-liquid mushy zone are discontinuous and transverse microstructure of α dendrites is worm-like feature.Growth direction of a phase is about 80° away from (0001〉α direction,and close to 〈 1120〉a direction.The corresponding lamellar orientation is aligned at the angle of about 10° to growth direction,which is consistent with α-dendrite growth direction according to Blackburn orientation relationship.Therefore,due to the altered growth direction of α phase,the lamellar orientation in Ti-45A1-7Nb alloy is controlled at the G/v ratio of 5 × 109 K· sm-2.