Material Science Test Assignment

All questions carry equal marks

1.The metal rubidium has a BCC crystal structure. If the angel of diffraction for the (321) set of planes occurs at (first order reflection) when monochromatic x-radiation having a wavelength of 0.0711 nm is used, compute (a) the interplanar spacing for this set of planes and (b) the atomic radius for the rubidium atom.

2.Phosphorus atoms are to be diffused into a silicon wafer using both predeposition and drive in heat treatments; the background concentration of Pin this material is known to be

. The predeposition treatment is to be conducted at for minutes; the surface concentration of P is to be maintained at a constant level of

. Drive in diffusion will be carried out at for a period of 2.5h.

For the diffusion of P in Si, values of and are and , respectively.a) Calculate the value of ,

b) Determine the value of for the drive in diffusion treatment.

3.Some hypothetical alloy is composed of 12.52 wt% of metal A and 87.35 wt% of metal B. If the densities of metals A and B are 4.27 and respectively, whereas their

respective atomic weights are 61.4 and , determine whether the crystal structure for this alloy is simple cubic, face centered cubic, or body centered cubic. Assume a unit cell edge length of 0.395 nm.

4.Suppose that a wing component on an aircraft is fabricated from an aluminum alloy that

has a plane strain fracture toughness of it has been determine

that fracture results at a stress of when the maximum internal crack

length is for this same component and alloy, compute the stress level at

which fracture will occur for a critical internal crack length of .

5.A alloy is heated to a temperature within the liquid phase region. if the mass fraction of each phase is 0.5, estimate a) The temperature of the alloyb) The compositions of the two phases