Hall-Petch Relation Calculation?

[Dave_]

Using the Hall-Petch relation, estimate the yield strength, σy, of a Cu-Zn alloy (brass) when the average grain diameter is 30 μm.

where:
σy = is the yield strength
σ0 = 25 MPa is the internal friction stress
k_y = 12.5 MPa·mm^1/2 is a material constant
d = is the average grain size

I get an answer of 97.17 MPa, is this correct, if not i'll post all of my working. Thanks!

 

[UltrafastPED]

This would require me to completely work out the problem myself!

We would much rather see your work, and then follow it to see if there is an error. The usual errors in a simple calculation like this are in the units.