Kirkendall Effect and Velocity Curve

Obviously, there is only one K-pIane with the markers located at the initial contact surface it moves at a parabolic dependence 

Therefore, we may use a simple geometric presentation of a K-plane it corresponds to an intersection of a straight line 

We can say that Ki and K3 must be stable, while the K2-plane must be virtual and unstable. Indeed, it corresponds to a positive slope of the velocity curve. So, a marker placed in front of the K-plane moves faster than it and does not return to it The marker, located behind the K-plane, has a smaller velocity and also leaves it 

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