form a twin in alpha iron. c)How does one distinguish slip bands and mechanical twins in the microstructure of alpha iron? 26 a)In term of the lattice parameters a,b,c,what is the interplanar spacing d for the following cases: (i)(121)planes,cubic (ii)(211)planes,cubic (iii)(12 1)planes,orthorhombic (iv)(211)planes,orthorhombic b)What is the linear density of atoms (i.e.,number of atoms per unit length along a line )along one of the close-packed direction in a bcc crystal? c)What is the planar density of atoms (i.e.,number of atoms per unit area of plane)for the most nearly close packed plane in a bcc crystal? 27.a)Discuss in detail the process of intersection of a gliding dislocation in alpha-brass with two (forest)dislocations lying on an intersecting glide plane and whose burgers vectors are also inclined to the glide plane of the moving dislocation. b)What is the importance of the Peierls barrier in controlling mechanical properties?What experimental evidence is there for the existence of such a barrier? 28.Suppose a binary alloy of aluminum in nickel was solution treated,quenched into the Ni3Al-Ni(Al)phase field and aged at a temperature adequate for the solid solution to decompose rapidly.Given that Ni(Al)is a random fee solid solution,Ni3Al is an ordered fee phase,and that the lattice parameters of Ni3Al and Ni(Al)are very similar yet not the same,answer the following questions: (a)What microstructure would you expect to see shortly after the beginning of the aging reaction and why would you expect to see it? (b)What changes (in detail,paying attention to the nature of interfaces) would you expect to occur within the microstructure as aging continues indefinitely.Give explanations. 29. Describe,with particular attention to the contrasts among,the various modes by which transformation of structure but not of composition can be affected in solid alloys You are given a series of micrographs labeled in order,A through F. a)Which of the micrographs shows evidence of or influence of (1)Twining (2)Plastic Deformationform a twin in alpha iron. c) How does one distinguish slip bands and mechanical twins in the microstructure of alpha iron? 26 a) In term of the lattice parameters a, b, c, what is the interplanar spacing d for the following cases: ( ) (1 ⅰ 2 − 1) planes, cubic ( ) (211) planes, cubic ⅱ ( ) (1 ⅲ 2 − 1) planes, orthorhombic ( ) (211) planes, orthorhombic ⅳ b) What is the linear density of atoms (i.e., number of atoms per unit length along a line ) along one of the close-packed direction in a bcc crystal? c) What is the planar density of atoms (i.e., number of atoms per unit area of plane) for the most nearly close packed plane in a bcc crystal? 27. a) Discuss in detail the process of intersection of a gliding dislocation in alpha-brass with two (forest) dislocations lying on an intersecting glide plane and whose burgers vectors are also inclined to the glide plane of the moving dislocation. b) What is the importance of the Peierls barrier in controlling mechanical properties? What experimental evidence is there for the existence of such a barrier? 28. Suppose a binary alloy of aluminum in nickel was solution treated, quenched into the Ni3Al-Ni(Al) phase field and aged at a temperature adequate for the solid solution to decompose rapidly. Given that Ni(Al) is a random fee solid solution, Ni3Al is an ordered fee phase, and that the lattice parameters of Ni3Al and Ni(Al) are very similar yet not the same, answer the following questions: (a) What microstructure would you expect to see shortly after the beginning of the aging reaction and why would you expect to see it? (b) What changes (in detail, paying attention to the nature of interfaces) would you expect to occur within the microstructure as aging continues indefinitely. Give explanations. 29. Describe, with particular attention to the contrasts among, the various modes by which transformation of structure but not of composition can be affected in solid alloys You are given a series of micrographs labeled in order, A through F. a) Which of the micrographs shows evidence of or influence of (1) Twining (2) Plastic Deformation