Study of $$ \{ 11\bar{2} 1\} $$ Twinning in α-Ti by EBSD and Laue Microdiffraction

Abstract

Activity of the f11 " 21gh " 1 " 126i extension twinning (T2) mode was analyzed in a commercial purity Ti sample after 2 pct tensile strain imposed by four-point bending. The sample had a moderate c-axis fiber texture parallel to the tensile axis. Compared with the many f10 " 12gh " 1011i extension (T1) twins that formed in 6 pct of the grains, T2 twins were identified in 0.25 pct of the grains by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) maps. Most of the T2 twins exhibited irregular twin boundaries (TBs) on one side of the twin. Highresolution EBSD revealed both intermediate orientations at some matrix/twin interfaces and substantial lattice rotation within some T2 twins. Interactions between matrix hc + ai dislocations 1 3 h1 " 213i and a f11 " 21g T2 twin were investigated by combining SEM/EBSD slip trace characterization and Laue microdiffraction peak streak analysis. hc + ai dislocations that originally glided on a pyramidal plane in the matrix were found on other planes in both the matrix and the twin, which was attributed to extensive cross-slip of the screw component, whose Burgers vector was parallel to the twinning plane. On the other hand, thickening of the twin could engulf some pile-up edge components in front of the TB. During this process, these hc + ai dislocations transmuted from a pyramidal plane ð0 " 111Þ in the matrix to a prismatic plane ð " 1010Þ T in the twin lattice. Finally, possible mechanisms for the nucleation and growth of T2 twins will be discussed.

Formation of {112¯1} twins from I1-type stacking faults in Mg: A molecu

“…6(c)). The observed relationship of the crystallographic orientation was consistent with the reported structure of a f1 1 2 1g twin [31,33]. The results of the MD simulations suggested that nucleation of the temporary hc þ ai dislocation was closely related to formation of the f1 1 2 1g twin.…”

“…The major f1 0 1 1g and f1 0 1 2g twins have been observed in conventional Mg alloys; furthermore, a minor f1 1 2 1g twin has recently been observed in Mg-Y alloys [27], Mg-Al-Gd alloys [28], and WE alloys [29]. In f1 0 1 1g and f1 0 1 2g twins, the system is rotated around the [ 2 1 1 0] axis [30], whereas the f1 1 2 1g twin is rotated around the [1 1 0 0] axis [31][32][33] (Fig. 1).…”

Effects of strain rates on deformation twinning behavior in α-titanium

“…n o twins had blocked or synergistic effects on the different dislocation slip systems, and pointed out that the dislocationtwin structure induced by deformation greatly contributed to the strength of the material, which was consistent with other results [11,15,16]. Research on dislocation-twin structure became a significant issue, and further study [17] found that the interaction between 1121 n o and (a + c) type dislocation slipping was beneficial to the strain hardening.…”

Toward understanding twin–twin interactions in hcp metals: Utilizing multiscale techniques to characterize deformation mechanisms in magnesium

“…This study attempted to infer the relative activity of each deformation mode and how each mode, and the interactions between modes, could be used to explain the overall deformation behavior. In a similar study, Wang et al [8] employed EBSD and slip trace analysis to study tensile twinning in titanium. The authors discussed the likely causes of nucleation and subsequent growth of twins in titanium, while recognizing the need for further study of boundary structure at the nanoscale.…”