Predict the crystal structure for MgO, on the basis of the ionic charge and ionic radii given in the table below.

Calculate the fraction of lattice sites that are Schottky defects for magnesium oxide at its melting temperature (2850°C). Assume an energy for defect formation of 2.5 eV.

Using the phase diagram below, for an alloy with the composition 30 wt% Pb-70 wt% Mg at 200°C, determine the phases present and the phase compositions (in wt% Pb) 

What is the maximum stress at the tip of an internal crack having a radius of curvature of 3×10^-4 mm and a crack length of 2×10^-2 mm when a tensile stress of 60 MPa is applied?

An alloy of composition 60 wt% Pb - 40 wt% Mg is heated to 300°C.  Using the same phase diagram for Mg-Pb as above, what is the composition (in wt% Pb) of the α phase? 

Your final answer should be in the format **

Using the phase diagram above, for the same alloy as in the previous question (60 wt% Pb-40 wt% Mg at 300°C), what is the mass fraction of the α phase? 

Your final answer should be in decimal format, *.**

A steel component must not fail when a tensile stress of 2500 MPa is applied.  Determine the maximum allowable surface crack length in nm if the surface energy of steel is 0.20 J/m².  Assume a modulus of elasticity of 200 GPa. Round up your answer to one decimal place.

Your final answer should be in the format *.*

What measures may be taken to increase the resistance to fatigue of a metal alloy?

Give the approximate temperature, in Kelvin, at which creep deformation becomes an important consideration for titanium. The melting temperature of titanium is 1,668°C. Round your answer to one decimal place.

Your final answer should be in the format ***.*