Rock Analog Experiments and notes by Dr. Win Means: 7b - Plastic Deformation, Grain Boundary Bulging, and Static Recovery in OCP. (cont.)

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Plastic Deformation, Grain Boundary Bulging, and Static Recovery in OCP. (cont.)
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37. Notice the grain boundary bulge of the yellow grain around (8,50). One expects some of these bulges to become new grains, by the bulge nucleation mechanism, but this very often does not happen. The bulges are present one moment and gone again the next. This is a general lesson learned from experiments of this type. Features that are prominent at one stage in a history may be completely gone soon after. One is impressed by the TRANSIENT quality of many microstructures.

38. Now there are prominent white and grey bulges along the boundary that passes diagonally through (50,20). Watch the grey bulge at (33,25) and the less promising-looking one at (53,20), which we will call bulges 1 and 2. The motor was turned off at this stage, but straining continued, at a decaying rate as the load decayed.

39. Five minutes after the motor was turned off. Bulge 1 has now developed a second lobe, to the left of the original one. There is a diffuse subgrain boundary separating these twin bulges from the host grain below. Bulge 2 has, unexpectedly, already developed somehow into a new grain.

40. Thirty five minutes after the motor was turned off. Bulge 1 has now developed into a full-fledged new grain (at 25,25), with a dark rectangular subgrain on its eastern margin. The grain that had grown from bulge 2 in the last picture now has a second lobe.

See how the brown subgrain at (58,7) has grown. Note the general coarsening of subgrains.

41. One hour and fifteen minutes after the motor was turned off. Much further coarsening has occurred, especially of the grains derived from bulges or subgrains of the original grains. Most subgrains have been eliminated.

By looking backwards and forwards through the images, it can be seen that the black grain at (30,50), the grey grain at (55,17), and the two white grains at (25,30) amd (50,35) are relatives. They all developed from parts of the big yellow grain in the center of the picture in image 33. The white grain at (35,60) and the two tan grains at (10,13) and (55,5), on the other hand, have different parentage. They are all offspring of the grey grain at (20,60) in image 33.

The tan grain at (55,5) is a nice example of a grain that has developed statically, by growth of a subgrain.

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Plastic Deformation, Grain Boundary Bulging, and Static Recovery in OCP. (cont.)	Click image to enlarge (~1MB)
37. Notice the grain boundary bulge of the yellow grain around (8,50). One expects some of these bulges to become new grains, by the bulge nucleation mechanism, but this very often does not happen. The bulges are present one moment and gone again the next. This is a general lesson learned from experiments of this type. Features that are prominent at one stage in a history may be completely gone soon after. One is impressed by the TRANSIENT quality of many microstructures.
38. Now there are prominent white and grey bulges along the boundary that passes diagonally through (50,20). Watch the grey bulge at (33,25) and the less promising-looking one at (53,20), which we will call bulges 1 and 2. The motor was turned off at this stage, but straining continued, at a decaying rate as the load decayed.
39. Five minutes after the motor was turned off. Bulge 1 has now developed a second lobe, to the left of the original one. There is a diffuse subgrain boundary separating these twin bulges from the host grain below. Bulge 2 has, unexpectedly, already developed somehow into a new grain.
40. Thirty five minutes after the motor was turned off. Bulge 1 has now developed into a full-fledged new grain (at 25,25), with a dark rectangular subgrain on its eastern margin. The grain that had grown from bulge 2 in the last picture now has a second lobe. See how the brown subgrain at (58,7) has grown. Note the general coarsening of subgrains.
41. One hour and fifteen minutes after the motor was turned off. Much further coarsening has occurred, especially of the grains derived from bulges or subgrains of the original grains. Most subgrains have been eliminated. By looking backwards and forwards through the images, it can be seen that the black grain at (30,50), the grey grain at (55,17), and the two white grains at (25,30) amd (50,35) are relatives. They all developed from parts of the big yellow grain in the center of the picture in image 33. The white grain at (35,60) and the two tan grains at (10,13) and (55,5), on the other hand, have different parentage. They are all offspring of the grey grain at (20,60) in image 33. The tan grain at (55,5) is a nice example of a grain that has developed statically, by growth of a subgrain.
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