Competition between prismatic and basal slip in hexagonal titanium–aluminum alloys with short-range order

Figures & data

Figure 1. Binding energies $E_b$ of Al pairs in α-Ti as a function of distance between solute atoms (a). Sketch of the hcp lattice indicating the five most strongly interacting NN configurations with the reference solute atom lying at R position (b). Crystal structure of the intermetallic ${\mathrm{T}\mathrm{i}}_3\mathrm{A}\mathrm{l}$ compound achieved by multiplication of the second and third NN Al pairs (c).

Figure 2. (a) Three geometrically possible prismatic and basal cutting modes of the second NN solute pair in α-Ti. (b) Initial $\zeta =0$ and final $\zeta =1$ positions of $1/3〈1\overline{2}10〉$ screw dislocation gliding next to isolated Al atom or cutting the second NN Al pair along prismatic and basal modes I–III. $Z_1$ and $Z_2$ indicate the position (normalized by the lattice parameter a) of solute atoms along dislocation line in the simulation box. Ti atoms belonging to different $\left(\overline{2}110\right)$ are plotted with open or full-colored circles. Solute atoms are denoted by yellow color. The corresponding minimum energy paths of particular prismatic and basal slip modes are given in (c), with the Peierls energy barriers of pure Ti marked by dashed lines.

Table 1. Activation energies $E^{\mathrm{a}\mathrm{c}\mathrm{t}}$ and its difference $\mathrm{\Delta }{E}^{\mathrm{a}\mathrm{c}\mathrm{t}}$ relative to pure Ti for a $〈a〉$ screw dislocation gliding in prismatic and basal planes in pure Ti and Ti–Al systems with distinct configurations of solute atoms. Activation energies are given in meV and are calculated for a single dislocation of length (Figure 2(b)).

Solutes configuration	Slip mode	$E^{\mathrm{a}\mathrm{c}\mathrm{t}}$	$\mathrm{\Delta }{E}^{\mathrm{a}\mathrm{c}\mathrm{t}}$
Pure Ti	Prism	71	0
	Basal	163	0
Ti + isolated Al	Prism	330	259
	Basal	501	338
Ti + Al SRO	Prism I	417	346
	Basal I	988	825
	Prism II	654	583
	Basal II	634	471
	Prism III	538	467
	Basal III	514	351

Figure 3. Core structure of the $〈a〉$ screw dislocation gliding on basal plane along isolated Al atom or cutting the second NNN Al pairs with I–III cutting modes. Selected states are the initial, maximum energy and final configuration of each glide mode from Figure 3. The arrows between atomic columns are proportional to the differential displacement created by the dislocation in the $\left[\overline{2}110\right]$ direction. Displacement smaller than 0.1b is not shown. The contour map shows the dislocation density according to the Nye tensor.

Figure 4. Core structure of the $〈a〉$ screw dislocation gliding on prismatic plane along isolated Al atom or cutting the second NNN Al pairs with I–III cutting modes. Selected states are the initial, maximum energy and final configuration of each glide mode from Figure 3. The arrows between two atomic columns are proportional to the differential displacement created by the dislocation in the $\left[\overline{2}110\right]$ direction. Displacement smaller than 0.1b is not shown. The contour map shows the dislocation density according to the Nye tensor.

Data availability

All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Any additional details are available from the corresponding author upon reasonable request.