Shear band mediated ω phase transformation in Nb single crystals deformed at 77 K

Figures & data

Figure 1. Shear band mediated ω phase transformation in Nb under (a,b) [100]-, (c,d) [110]- and (e,f) [111]-compression, respectively. The compression strains for [100], [110], and [111]-samples are 20%, 20%, and 15%, respectively. The viewing direction of (a,b,e,f) are along the [011]_BCC//[$\overline{1}\overline{1}20$]_ω and (c,d) are along the [$\overline{1}$13]_BCC//[$\overline{1}\overline{1}$23]_ω.

Table 1. Largest Schmid factors on the 110<11$\overline{1}$> and 112<11$\overline{1}$> dislocation slip systems for three loading orientations tested in Nb.

	Schmid factor
Loading orientation	110<11$\overline{1}$>	112<11$\overline{1}$>
[100]	0.408	0.471
[110]	0.408	0.471
[111]	0.272	0.314

Figure 2. Structural evolution of sheared ω phase transformation at a 112 shear band boundary. (a) A series of structures featuring the shear-induced ω phase transformation. (b,c) show a change in the BCC structure, and (c,d) shows the ω phase transformation. Scale bar, 0.5 nm. (e) Ideal atomic model of BCC structure and ω phase.

Figure 3. Atomic shuffle of ω phase transformation. (a) Differences between the shuffle/dislocation mechanisms. (b) HRTEM image and (c) comparison of intensity profiles for atom columns along red and blue lines. Scale bar, 0.5 nm.

Figure 4. DFT calculations of BCC and ω phase under 112<11$\overline{1}$> shear strain. (a) The supercell model of BCC and ω phase under the same shear strain. (b) Effect of shear strain on the energy of BCC and ω phase. (c) The BCC-ω supercell models identical to the experimental observation. (d) Effect of the shear strain on the energy of BCC-ω supercell model.

Figure 5. Schematic illustration showing the formation process of shear band mediated ω phase transformation in Nb.