a. data show that a material with an average grain size of 40 um has a yield strength of 150 MPA, whereas the same type of material with an average grain size of 2 um has a yield strength of 422 MPA. Calculate the Go and ky values by using the Hall-Petch equation (Oy = 0o + kyd-/2). Calculate the yield strength value for a material with an average grain size of 10 m and calculate the grain size of a material with a yield strength of 350 MPA. Oy (MPa) 150 422 d (um) 40 2