AN IN SITU STUDY ON DISLOCATION BEHAVIOR OF CRACK TIP IN Ti 3Al-Nb ALLOY
(1.School of Materials Science and Engineering; Harbin Institute of Technology; Harbin 150001 ;
2. Detecting Center; Taiyuan University of Technology; Taiyuan 030024)
2. Detecting Center; Taiyuan University of Technology; Taiyuan 030024)
Abstract: A direct observation was made on the dislocation behavior at crack tip of Ti 3Al Nb alloy during tensile deformation at an H 800 TEM. The results indicate that dislocations are found to emit from the crack tip and form a plastic deformation zone (PZ) when the crack tip was tensioned. The motion of dislocations needs to surpass the P N potential barrier, and dislocations are distributed in the form of inverse pile up in the plastic deformation zone. No dislocation free zone (DFZ) ahead of the crack tip was found. Dislocations in the whole PZ are composed of a type (b=1/6<1120>) and c type (b=1/3<0003>) superpartials on prismatic planes {1010}. No c+a/2 type dislocations and twinnings were found. The interface of α2/α2 in front of the crack tip is an obstacle to the motion of dislocations.
Key words: Ti 3Al-Nb alloy tensile deformation crack propagation dislocation