Consider stage i, ii, and iii of work hardening in a single phase metal. what are the expected dislocation interactions. classify them as hard or soft obstacles. 2) consider a precipitation-hardened system having the following characteristics: lattice parameter of the precipitate is 5% greater than that of the matrix, g of the matrix is 50 gpa while that of the precipitate is 60 gpa, the matrix burgers vector is 0.25 nm, precipitate matrix surface energy is 0.25j/m^2, apbe of precipitate is 0.1 j/m^2. consider coherency, modulus, chemical and order hardening. determine the relative increase in strength accompanying each mechanisms. consider particles with r=10b and r=100b. (now of course if this were a quiz question you would need substantially more information. however, i could ask a simpler version) 3) during irradiation voids can be generated in a metal. could the presence of these defect potentially strengthen the metal? if "yes" provide a discussion of the mechanism. 4) as we will discuss in the next lecture al-li alloys if quenched will remain as a supersaturated solid solution. on aging at 450k, the supersaturated solid solution decomposes into an al-rich matrix and al3li, a metastable precipitate phase. assume an initial li content of 10% (atomic), a post aging volume fraction of al3li of ~0.22 and a reduction of the li content in the matrix to 7%. which do you expect to be stronger the supersaturated solid solution or the aged alloy. make some estimates of the yield strength of each relative to pure aluminum. 5) based on you knowledge so far describe how to design an optimal solid solution strengthened alloy and an optimal precipitation strengthened alloy (we will revisit this question multiple times over the semester).