Dynamics of twin layer widening in In‐Pb crystals

Abstract

AbstractThe authors studied mobility of boundaries of plane‐parallel twin layers in In‐0.2 wt.% Pb and In‐2 wt.% Pb crystals in the temperature range 290–373 K when stresses are applied τ/G = (1.35 – 7) × 10−6 (G is the shear modulus). They found that lead concentration increase as well as dislocation structure deterioration result in lower boundary velocity for a constant stress.In In‐2 wt.% Pb crystals, the boundary velocity is well describable as Vn = V0(τ) × × exp [ − ΔH (τ)/kT] where V0(τ) = Aeατ/G (A = 10−3 cm/s, α = 1.1 × 106) τ ΔH(τ) is the activation energy depending on the stress, ranging under these circumstances from 0.33 to 0.43 eV.At present it is difficult to interpret the results at hand. The analysis allows only to assume that the change in the boundary movement activation energy for impure crystals as against that for pure ones can be associated with the impurity effect on the structure of the intermediate zone between the twin and the matrix. The dependence of the pre‐exponential factor on the stress is probably due to the effect of the internal long‐range stress field on sources of twinning dislocations.Comparison with data for calcite and pure indium shows that twin boundary mobility parameters and their dependence on the stress are governed by the crystal type and defect structure.