Changes in the texture of the plastic deformation zone at the tip of a moving crack

1.	Sheets of the Zr- 1% Nb alloy were used for the first time to show by experiments the crystallographic reorientation of the grains at the tip of the moving crack.
2.	The effects detected by x ray diffraction examination in the vicinity of the fracture of the specimens with the notch, were compared with the effects recorded in the volume of similar smooth specimens subjected to tensile loading. According to the estimates, in the layer up to 20m thick, adjacent to the fracture surface, the average strain of the material in tensile loading is 15–20% for the RD specimen and 3–5% for the TD specimen.
3.	Anisotropy of the cracking resistance and development of the zone of plastic deformation at the tip of the moving crack are determined by the activating mechanism of plastic deformation of alpha zirconium whose special feature is the strong dependence on the crystallographic orientation of the grains.

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 27, No. 5, pp. 56–61, September–October 1991.