Cyclic deformation behavior of high-purity titanium single crystals: Part II. Microstructure and mechanism

Abstract

Strain-controlled cyclic tests have been conducted on high-purity titanium single crystals with different orientations. The fatigue mechanisms of the titanium crystals were studied by means of a scanning electron microscope (SEM) and a transmission electron microscope (TEM). It was found that single slip lines, wavy slip lines, double slip lines, twins, and associated slip lines occurred in differently oriented single crystals. A new type of fractographic morphology, parallel traces, was observed. Dislocation patterns and cyclic twins, as well as the mechanical response, were analyzed. The dependence of the deformation mechanisms on the orientations of the single crystals is discussed. (0002), and furrows in the [0001] direction. X. TAN, Postdoctoral Fellow, formerly with the Research Institute for Strength of Metals, Xi'an Jiaotong University, is with the Hemispheric

Experimental Characterization and Crystal Plasticity Modeling of Heterogeneous Deformation in Polycrystalline α-Ti

“…Unlike fcc materials that usually have only one slip mode f111g 10 " 1 À Á ; there are at least four reported slip modes in a-Ti: three instances of 0001 f g 1 " 210 basal slip, three of 10 " 10 È É 1 " 210 prismatic slip, six of 10 " 11 È É 1 " 210 pyramidal hai slip, and twelve of 10 " 11 [26,27] Among them, prismatic slip has the lowest CRSS, and is therefore the primary slip mode in a-Ti. [26][27][28][29][30] Table I summarizes the material parameters used in this model. Basal, prismatic, and pyramidal c þ a h i are the three slip modes that were included in the current simulation.…”

Twin Nucleation by Slip Transfer across Grain Boundaries in Commercial Purity Titanium

“…[1][2][3] Experiments on single-crystal high-purity titanium showed that the critical resolved shear stress for prismatic slip is much lower than that of other slip modes: 0001 f g 1 " 210 basal slip, 10 " 11 È É 1 " 210 pyramidal hai slip, and 10 " 11 È É 2 " 1 " 1 " 3 pyramidal hc+ai slip. [4] Nevertheless, the prismatic slip mode alone is not sufficient to accommodate an arbitrary plastic strain, which, according to the von Mises criterion, requires five independent slip systems. [5] As a result, nonprismatic slip and deformation twinning are also necessary to achieve significant plastic deformation in polycrystalline titanium.…”

Cyclic deformation behavior of high-purity titanium single crystals: Part I. Orientation dependence of stress-strain response

“…When the microstructural observations shown in Part II of this study [22] are combined with the geometric analysis results, a map of the orientation de- pendence of the cyclic deformation modes in titanium single crystals can be prepared ( Figure 6). Partic-2 ularly, the contribution of {10 0} slip to cyclic plastic de-1 formation should be weighted against with the other deformation modes.…”