Migration mechanism of <110> tilt boundaries in nickel

Abstract

The features and migration mechanism of tilt boundaries with the misorientation axis <110> in an fcc crystal using nickel as an example were studied by the method of molecular dynamics. The dependences of the boundaries energy and the rate of their migration at a temperature of 1700 K on the misorientation angle are obtained. It is shown that the migration rate of <110> tilt boundaries under the same conditions is an order of magnitude lower than the migration rate of <111> and <100> boundaries, which is primarily due to the relatively low energy of <110> boundaries. In addition, the low-angle <110> tilt boundaries are unique compared to other tilt boundaries-grain boundary dislocations in them are ordinary perfect edge dislocations with straight cores that do not contain jogs periodically located on them, as in <111> and <100> boundaries. In <110> boundaries, as well as in <111> and <100> boundaries, there are two different sets of dislocations, but they are not always combined, as is often the case in <111> and <100> boundaries. Combined dislocations in <110> boundaries turned out to be less mobile during boundary migration than non-combined ones. An analogy of migration mechanisms of low-angle <110> boundaries with the previously considered <111> and <100> boundaries was noted. During migration, in the grain towards which the migration took place, regions of the same shape orderly rotated through the angle of misorientation were formed, the size of which depended on the distance between neighboring grain boundary dislocations.

Interaction of an edge dislocation with a 〈110〉 tilt boundary in nickel: molecular dynamics simulation

“…An edge dislocation overcomes the 〈110〉 low-angle boundary at much lower stresses than a coherent twin. tilt boundaries [20]. Grain-boundary dislocations in 〈110〉 boundaries belong, as it were, simultaneously to slip systems on both sides of the boundary.…”

“…Low-angle 〈110〉 tilt boundaries are unique compared to other tilt boundaries -grain boundary dislocations at such boundaries are ordinary perfect edge dislocations with straight cores that do not contain jogs on them. At the tilt boundaries with other misorientation axes, for example with 〈111〉 and 〈100〉 axes, grain boundary dislocations are more complex [20].…”