Successive gliding of twinning disconnections (TDs) creates three-dimensional twins in parent crystal and accommodates shear deformation. It is generally recognized that TD is subject to the same Peierls stress as it glides forward or backward because of its dislocation character and the twofold rotation symmetry of the twin plane. Based on atomistic simulations, we demonstrate that the glide of TDs may be subject to a symmetric or asymmetric resistance corresponding to step character, symmetric resistance for A/A type steps but asymmetric resistance for A/B type steps, where A and B represent crystallographic planes in twin and matrix. Furthermore, we experimentally demonstrate that the asymmetric resistance results in asymmetric propagation and growth of twins in Mg alloys.

孪晶断开 (TD) 的连续滑动在母晶体中产生三维孪晶并适应剪切变形。一般认为，TD由于其位错特性和双平面的双重旋转对称性而在向前或向后滑动时受到相同的Peierls应力。基于原子模拟，我们证明了 TD 的滑动可能会受到与台阶特征相对应的对称或不对称阻力，A/A 型台阶的对称阻力，但 A/B 型台阶的不对称阻力，其中 A 和 B 代表晶体学孪生和矩阵中的平面。此外，我们通过实验证明不对称电阻导致镁合金中孪晶的不对称传播和生长。