Migration of special 〈110〉 tilt boundaries in aluminum bicrystals

Kinked Grain Boundaries in Alumina Doped with Y2O3

“…The formation of a kink with a flat segment on one side, which may occur by nucleation and growth, is thus analogous to precipitation of a compound phase in a solution with a composition gradient as pointed out earlier. 2 If the grain-boundary Wulff shape has both flat (singular) and curved (rough) segments, a kink can have a flat boundary segment on one side and a curved segment on the other as is frequently observed 21,22,27 and shown, for example, for the boundary segment indicated by an arrow in Fig. 4.…”

“…The smoothly curved rough grain boundaries in pure alumina were previously observed to develop kinks when heat-treated at temperatures below 1100°C. 2 Kinked grain boundaries were also observed in such metals as Al, 21,22 Zn, 23,24 Ag, 25,26 and Si-Fe. 27,28 The development of a grain-boundary kink is essentially a process of forming the edge of an island grain embedded in another grain of the corresponding misorientation with an equilibrium shape (grain-boundary Wulff shape) that consists of either only flat (singular) segments or both flat and curved (rough) segments.…”

“…The kinked grain boundaries characterized by sharply changing boundary orientations were previously referred to also as faceted grain boundaries. [21][22][23][24]26 Because of the possible implication that the boundary segments intersecting at the kinks are flat, a kinked boundary appears to be a more appropriate term as suggested by Weins and Weins. 25…”

Facet–Defacet Transition of Grain Boundaries in Alumina

“…Kinked grain boundaries were observed also in metallic bicrystals. 6,7,9,10,12,13,18,19 These observations thus show that at least some of the grain boundaries in alumina undergo reversible roughening-singular transition at temperatures below about 1100°C. It is possible that most of the grain boundaries still do not show the singular transition because of slow kinetics.…”

“…G RAIN boundaries of hill-and-valley (h&v) shapes with alternating parallel segments or kinked shapes (as observed at cross sections) with flat or curved segments intersecting at joints have been observed in many metals (Au, [1][2][3] Ni, 4,5 Al, 2,6,7 Ag, 8 -10 Cu, 11 Zn, 12,13 316L stainless steel, 14,15 a Ni-base superalloy, 16 Si-Fe, [17][18][19] Cu-Bi, 20 -22 and Fe-Te 23,24 ) and some oxides (MgO, 25 MgO⅐2Al 2 O 3 , 26 NiO, 27 Al 2 O 3 , 28 -34 and BaTiO 3 35-39 ) with both special and general misorientation angles between the grains. Some flat segments of the h&v boundaries were parallel to low-index planes of one or both of the grain pairs 1,3,28,32,34 -39 and likely to be singular corresponding to cusps in the polar plot of the boundary energy ␥ against the normal direction.…”