Microstructure and textural evolution during cold rolling and annealing of commercially pure titanium sheet

The effects of cold rolling and annealing on the microstructure and textural evolution of a commercially pure titanium (CP-Ti) sheet were investigated. Electron backscatter diffractometry demonstrates that the deformation during rolling is accommodated by twinning and slip. Additionally, twinning is the dominant deformation mechanism when the cold rolling reduction is less than 40%. During rolling, $\left\{11\overline{2}2\right\}〈11\overline{2}\overline{3}〉$ contraction twinning (CT) and $\left\{10\overline{1}2\right\}〈10\overline{1}1〉$ extension twinning (ET) are activated. And, the intensity of the (0002) pole along the ND gradually increases with increasing deformation. During annealing, the fraction of low angle grain boundaries (LAGBs) and the intensity of the (0002) pole along the ND gradually decrease slightly with increasing annealing time, while twinning lamellae disappear rapidly. When the annealing time reaches 60 min, 20% cold-rolled sheet recrystallizes almost completely.     

Atomistic simulations of interactions between screw dislocation and twin boundaries in zirconium

Molecular statics was employed to simulate interaction between screw dislocation and twin boundaries (TB) in hexagonal close-packed zirconium. In the moving TB model, the interaction of a moving $\left\{10\overline{1}2\right\}$ TB with a static $1/3〈11\overline{2}0〉\left\{10\overline{1}0\right\}$ screw dislocation was investigated. Twinning dislocation (TD) nucleation and movement play an important role in the interaction. The screw dislocation passes through the moving TB and changes to a basal one with a wide core. In the moving dislocation model, a moving $1/3〈11\overline{2}0〉\left\{10\overline{1}0\right\}$ dislocation passes through the TB, converting into a basal one containing two partial dislocations and an extremely short stacking fault. If the TB changes to the $\left\{10\overline{1}1\right\}$ one, the moving $1/3〈11\overline{2}0〉\left\{10\overline{1}0\right\}$ prismatic screw dislocation can be absorbed by the static TB and dissociated into two TDs on the TB. Along with the stress–strain relationship, results reveal the complicated mechanisms of interactions between the dislocation and TBs.     

Atomic scale structural characterization of {101¯2} twin boundaries in zinc

The structure and the migration mechanisms of $\left\{10\overline{1}2\right\}$ twin boundaries (TBs) of pure zinc deformed by rolling were studied using high-resolution transmission electron microscopy (HRTEM) at atomic scale. We found the presence of basal/prismatic (BP/PB) planes serrations on $\left\{10\overline{1}2\right\}$ TBs and the coexistence of two kinds of TBs with different structures in the same $\left\{10\overline{1}2\right\}$ twin: TBs composed of $\left\{10\overline{1}2\right\}$ coherent twin boundaries (CTBs) plus short BP/PB serrations, and TBs composed of successive BP/PB segments without $\left\{10\overline{1}2\right\}$ CTBs. The formation of BP/PB serrations has no relation to the c/a ratio of hexagonal-close-packed (HCP) metals because the BP/PB serrations are energetically preferred and geometrically favored. Based on dislocation theory, we proposed the migration mechanisms of the TBs to be the glide of twinning dislocations (TDs) on the CTBs and the climb of interface dislocations (IDs) on the BP/PB segments.     

Orientation dependence of shock-induced twinning and substructures in a copper bicrystal

Shock recovery experiments have been conducted to assess the role of shock stress and orientation dependence on substructure evolution and deformation twinning of a [1 0 0]/$[01\overline{1}]$ copper bicrystal. Transmission electron microscopy of the post-shock specimens revealed that well-defined dislocation cell structures developed in both grains and the average cell size decreased with increasing shock pressure from 5 to 10 GPa. Twinning occurred in the [1 0 0] grain, but not the $[01\overline{1}]$ grain, at the 10 GPa shock pressure. The stress and orientation dependence of incipient twinning can be predicted by the stress and orientation conditions required to dissociate slip dislocations into glissile twinning dislocations. The dynamic widths between the two partials are calculated considering the three-dimensional deviatoric stress state induced by the shock as calculated using plane-strain plate impact simulations and the relativistic and drag effects on dislocations moving at high speeds.     

AZ91镁合金热轧退火过程中的织构演变

将具有随机初始织构的工业 AZ91镁合金在450°C 进行均匀化热处理。经热处理后,合金中出现弱的{0001}-{1010}-{1120}三重纤维织构。经400°C热轧后,合金的变形织构是典型的(0001)基面,其基极沿轧制方向分裂。在450°C 退火36 h后,其残余变形织构中的基极沿基面分布更均匀,没有出现晶粒的异常长大。     

Nucleation potency prediction of LaB6 with E2EM model and its influence on microstructure and tensile properties of Al-7Si-0.3Mg alloy

The edge-to-edge matching (E2EM) crystallographic model was used to predict the orientation relationships (ORs) between LaB₆ and Al. Three different possible ORs can be predicted between LaB₆ and Al, which are ${\left(100\right)}_{\text{Al}}6{\left(100\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[001\right]}_{\text{Al}}6{\left[001\right]}_{{\text{LaB}}_{\text{6}}}$; ${\left(110\right)}_{\text{Al}}6{\left(110\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[001\right]}_{\text{Al}}6{\left[001\right]}_{{\text{LaB}}_{\text{6}}}$; and ${\left(111\right)}_{\text{Al}}6{\left(111\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[01\overline{1}\right]}_{\text{Al}}6{\left[01\overline{1}\right]}_{{\text{LaB}}_{\text{6}}}$. The prediction results are perfectly confirmed through TEM analysis and prove the nucleation potency of LaB₆. The refining efficacy of Al-2La-1B refiner and its influence on the tensile properties were investigated in the as-cast Al-7Si-0.3Mg alloy. According to the results, LaB₆ has higher nucleation potency than TiB₂, leading to better grain refining efficacy of Al-2La-1B refiner in the as-cast Al-7Si-0.3Mg alloy. Regarding the mechanical performances, tensile properties of the as-cast Al-7Si-0.3Mg casting alloy are prominently improved after addition of Al-2La-1B refiner, due to the refined microstructures.