AN IN SITU STUDY ON DISLOCATION BEHAVIOR OF CRACK TIP IN Ti ₃Al-Nb ALLOY

À´Ô´ÆÚ¿¯£ºÖйúÓÐÉ«½ðÊôѧ±¨(Ó¢ÎÄ°æ)1997ÄêµÚ3ÆÚ

ÂÛÎÄ×÷ÕߣºWu Ying Zhen Liang Yang Dezhuang Liang Wei

ÎÄÕÂÒ³Â룺31 - 37

Key words£ºTi ₃Al-Nb alloy£» tensile deformation£» crack propagation£» dislocation

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 ª§¦Á₂/¦Á₂ª§ in front of the crack tip is an obstacle to the motion of dislocations.