Formation of a Dislocation Structure of the Accommodation Zone in a System of Two Mechanical twins in Titanium

Purpose. Experimental study and mathematical modeling of the processes of structure formation in the accommodation zone of a system of wedge-shaped twins in commercially pure titanium.

Methods. Methods of Microindentation, chemical etching, mathematical modeling and electron probe microscopy were user.

Results. While forming of wedge twin in poly-crystal of titanium are forming conditions of formation of additional twin in its transition zone. Forming of the extra twin is some way of relaxation of high stresses in the tips. The performed mathematical modeling of the stress distribution in the region of the twinning process, taking into account the presence of the detected accumulation of formed low-angle boundaries, makes it possible to state that the interaction of structural defects with defects formed during the development of the twinning layer is regular. The proposed model indicates that the formation of low-angle boundaries due to the interaction of existing material defects and twinning dislocations leads to a change in the stress diagram in the transition area, which, in turn, generates multiple low-angle borders in the form of the dislocation walls. Shown physical mechanism and mathematic model gives rather clear picture of forming of structure and spreading stresses in zone of forming of two parallel twins.An accumulation of low-angle boundaries was found in the accommodation zone of the wedge-shaped twin, which were regularly formed during its growth.

Conclusion. In the work, we have presented the results of experimental studies and mathematical modeling for the processes of the structure formation in a transition zone of wedge-type twins system in commercially pure titanium. The process of interaction of structure defects with twinning dislocations during the formation of a wedge-type twin was taken into consideration. It is shown that the interaction alters the stress maximum in vicinity of boundaries in the system two wedge-type twins.

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