The following data is given D mol//RT)cm2/s Plate thickness 0.3 m vessel diameter 3m T=400C throughout the plat (b) Give a numerical estimate of the time to diffuse 90% of the gas out of the metal (c) Outline how a more exact calculation of the transient could be made Why do interstitials generally produce greater hardening than substitutional solute atoms? How does the effect vary in different crystal structures? Question No. 17 a binary alloy is solution treated. Quenched to and aged at a temperature at which continuous precipitation of a stable phase takes place. In this system the precipitates nucleate homogeneously and growth is controlled by long range diffusion, for which the invariant field approximation is applicable. Discuss the characteristics of the transformation from the very beginning of the aging time to very long times. Consider the nature of the precipitate, the number of precipitates and their average sizes. uestion No Discuss the tress needed to operate a frank-Read source with one end intersecting a free surface What approximations did you make? If the Burgers vector is inclined at an angle of 30 to the surface, what would be the configuration of the dislocation with no stress applied Question No. 19 (a) The basic symmetry elements used in crystallography are rotations, inversions, reflections, and translations. There are also combinations such as rotation-inversion rotation-translation (screw axis), and reflection-translation(glide plane). Give one example of each, using simple sketches of stereograms(stereographic projections showing equivalent points) (b) Let the Z-axis be along the [110] direction of a BCC crystal. Sketch a stereogram to show the equivalent points consistent with the presence of this axis only (i.e, ignore all other symmetry elements present). Then use matrix methods to prove that these are the only equivalent points present for this case (c)The(110) plane is one of the mirror planes in cubic crystals. Write down the relations between the coordinates of any selected point in the lattice and the corresponding point obtained by reflection. From this, obtain the matrix for the reflection involving(110)as the mirror plane That two reflections bring one back to the original point. You may translate coordinates if this the(200)pla (d) Provide the appropriate Miller indices for the point a-f, for the given standard projection of a cubic crystal. A right hand coordinate system is usedThe following data is given: DH Fe = 0.5 exp (-6000(cal/mol/)/RT) cm2 /s Plate thickness 0.3 m, vessel diameter 3m. T=400C throughout the plate. (a) Skatch the concentration profile through the wall at t=0 (b) Give a numerical estimate of the time to diffuse 90% of the gas out of the metal. (c) Outline how a more exact calculation of the transient could be made. Question No. 16 Why do interstitials generally produce greater hardening than substitutional solute atoms? How does the effect vary in different crystal structures? Question No. 17 A binary alloy is solution treated. Quenched to and aged at a temperature at which continuous precipitation of a stable phase takes place. In this system the precipitates nucleate homogeneously and growth is controlled by long range diffusion, for which the invariant field approximation is applicable. Discuss the characteristics of the transformation from the very beginning of the aging time to very long times. Consider the nature of the precipitate, the number of precipitates and their average sizes. Question No. 18 Discuss the tress needed to operate a Frank-Read source with one end intersecting a free surface. What approximations did you make? If the Burgers vector is inclined at an angle of 30 to the surface, what would be the configuration of the dislocation with no stress applied? Question No. 19 (a) The basic symmetry elements used in crystallography are rotations, inversions, reflections, and translations. There are also combinations such as rotation-inversion, rotation-translation (screw axis), and reflection-translation (glide plane). Give one example of each, using simple sketches of stereograms (stereographic projections showing equivalent points). (b) Let the Z-axis be along the [110] direction of a BCC crystal. Sketch a stereogram to show the equivalent points consistent with the presence of this axis only (i.e., ignore all other symmetry elements present). Then use matrix methods to prove that these are the only equivalent points present for this case. (c) The (110) plane is one of the mirror planes in cubic crystals. Write down the relations between the coordinates of any selected point in the lattice and the corresponding point obtained by reflection. From this, obtain the matrix for the reflection involving (110) as the mirror plane. That two reflections bring one back to the original point. You may translate coordinates if this is helpful. Repeat procedure for the (200) plane. (d) Provide the appropriate Miller indices for the point a-f, for the given standard projection of a cubic crystal. A right hand coordinate system is used