J. P. Hirth et al. cta Materialia 54(2006 )1917-192 normal to[1001 h 702] a δ 02 b Fig. 2. Free surface ledges on the a and a phases(a) brought Fig 4. Single (010)layer of the a monoclinic phase, showing six unit form a disconnection(b). Ledge overlap produces a step h. cells, the three[100][302 and [102] pseudo-close-packed directions, and Difference in height and inclination produces a dislocation 02], and [102] shear transformation directions. The nents bi and bx. 5 is the line direction. vectors in the diagram correspond to Shockley partials in the hcp pseudolattice. The larger unit cell shown in Fig. I is also shown here in dashed lines. Note that the dashed lines are parallel to [100] and[102 (010)a(normal to x2), the line direction 5 is [100](parallel x3),and xI- direction is parallel to one of the(1010 structure. The 5 angular difference between the latter directions in the hcp pseudostructure which in turn is two directions is allowed for in the next section. The inter- approximately parallel to the [102] direction in the o face-plane component of the Burgers vector of the disco 10 um Fig 3. Optical photomicrograph of a Pu-2 at. %Ga alloy following cooling to-155C, holding for 60 min, and warming to room temperature. Note the light-colored paths of a-Pu within the 8-Pu matrix. Gray-scale variations within grains show that the lighter cores of the grains are relatively rich in Ga Note that the paths have four orientations in each grain, corresponding to the four lll planes in the 8 matrix(0 1 0)a (normal to x2), the line direction n is [1 0 0]a (parallel to x3), and x1-direction is parallel to one of the h1 01 0i directions in the hcp pseudostructure which in turn is approximately parallel to the [1 0 2]a direction in the a0 structure. The 5 angular difference between the latter two directions is allowed for in the next section. The inter￾face-plane component of the Burgers vector of the discon￾Fig. 3. Optical photomicrograph of a Pu–2 at.% Ga alloy following cooling to 155 C, holding for 60 min, and warming to room temperature. Note the light-colored paths of a0 -Pu within the d-Pu matrix. Gray-scale variations within grains show that the lighter cores of the grains are relatively rich in Ga. Note that the paths have four orientations in each grain, corresponding to the four {1 1 1} planes in the d matrix. [1 02] [100] [3 02 ] [102 ] normal to [100 ] [7 02 ] [502 ] 1 24 [7 02 ] 1 24 [50 2 ] 1 12 [102 ] 5˚ Fig. 4. Single (0 1 0) layer of the a0 monoclinic phase, showing six unit cells, the three [1 0 0], ½3 02, and ½102 pseudo-close-packed directions, and the three ½5 02, ½7 02, and [1 0 2] shear transformation directions. The vectors in the diagram correspond to Shockley partials in the hcp pseudolattice. The larger unit cell shown in Fig. 1 is also shown here in dashed lines. Note that the dashed lines are parallel to [1 0 0] and ½102 pseudo-close packed directions. Fig. 2. Free surface ledges on the a0 and d phases (a) brought together to form a disconnection (b). Ledge overlap produces a step of height h. Difference in height and inclination produces a dislocation with compo￾nents b1 and b2. n is the line direction. 1920 J.P. Hirth et al. / Acta Materialia 54 (2006) 1917–1925