An atomic displacive model for {10(1)over-bar2}<(1)over-bar011 > twinning in hexagonal close packed metals with the emphasis on the role of partial stacking faults in formation of {10(1)over-bar2} twins

作者：Namakian Reza; Voyiadjis George Z^*

来源：Acta Materialia, 2018, 150: 381-393.

DOI：10.1016/j.actamat.2018.03.028

• Partial stacking fault
• Extension twinning
• Crystallography
• Shearing
• Shuffling

Anomalous basal type stacking faults (SFs) called partial SFs (PSFs) have been observed extensively within {10 (1) over bar2} or extension twins for a variety of hexagonal close packed (HCP) metals. The formation of PSFs can generate a stacking sequence in which every other basal plane has been displaced by a (1/3)< 10 (1) over bar0 > vector. Based on this special structural property of HCP metals, a new crystallographic model is developed for {10 (1) over bar2}<(1) over bar 011 > twinning system. In contrast to homogenous lattice shearing process in classical twinning model, the new model describes that formation of PSFs can provide transient locations of atoms in such a way that a subsequent zonal-twinning mechanism including a set of relatively simple shear and shear-shuffle atomic displacements toward twinning direction is sufficient to accomplish {10 (1) over bar2}<(1) over bar 010 > twinning. These shear and shear-shuffle atomic displacements are formally determined, and their analytical expressions are given in a generalized explicit form for a whole twinned domain of any HCP crystal with c/a ratio between 1.5 and 1.9. It will be shown that the macroscopic effect of spontaneous cooperative movements of atoms in the new mechanism is a simple shear, and the invariant plane strain condition of {10 (1) over bar2} or twinning plane is preserved.

• 出版日期2018-5-15