The lower yield point for an iron that has an average grain diameter of 5x10^-2mm is 135 MPa. At a grain diameter of 8x10^-3, the yield point increases to 260 MPa. At what grain diameter will the lower yield point be 205 MPa?
Homework Equations
Hall-Petch Equation:
σy = σo + ky(d^-(1/2))
The...