fig5

Figure 5. Processing methods for forming grain gradient structure. (A) SMGT^[67]. (Reprinted from Ref.^[67], with permission from Elsevier). (B) Surface rotational rolling^[72]. (Reprinted from Ref.^[72], with permission from Elsevier). (C) Single-roll angular rolling^[74]. (Quoted with permission from Lee et al.^[74], under the CC BY license, http://creativecommons.org/licenses/by/4.0/). (D) Rotary swaging^[76]. (Reprinted from Ref.^[76], with permission from Elsevier). (E) High-pressure torsion^[79]. (Reprinted from Ref.^[79], with permission from Elsevier). (F) Direct-current electrodeposition^[80]. (Reprinted from Ref.^[80], with permission from Elsevier).