The distributions of forces and stresses along a thin twin layer were analyzed on the basis of the experimentally measured locations of twinning dislocations in the layer. The results showed that both the forward stress and the back stress were very large at the twin tip, and then decreased quickly as the distance from the twin tip increased. The forward stress and the back stress were equal to 1140 and 1200MPa, respectively, on the first twinning dislocation and equal to 275 and 300MPa, respectively, on the sixteenth twinning dislocation. The external stress was found to be the residual stress in the matrix, and it was uniformly distributed along the thin twin layer. The magnitude of the residual stress was about 50MPa. The internal friction stress on the first twinning dislocation was near to 765MPa, but the internal friction stress on the second twinning dislocation was lower than that on any twinning dislocation behind it. The high internal friction stress on the first twinning dislocation was attributed to a compressive stress that was normal to the twinning plane, and to a tensile stress in the twinning direction within the core of the first

twinning dislocation besides the core structural change in the first twinning dislocation. A high stress concentration at a twin tip was an intrinsic property of a growing twin layer, but the stress concentration for an unblocked twin had an upper limit of 1200MPa.

Z.Jin, T.R.Bieler: Philosophical Magazine A, 1995, 72[5], 1201-19