Answer:
3.115× [tex]10^{-3}[/tex] meter
Explanation:
hall-petch constant for copper is given by
[tex]S_0[/tex]=25 MPa
k=0.12 for copper
now according to hall-petch equation
[tex]S_Y[/tex]=[tex]S_0[/tex] +[tex]\frac{K}{\sqrt{D}}[/tex]
240=25+[tex]\frac{0.12}{\sqrt{D}}[/tex]
D=3.115× [tex]10^{-3}[/tex] meter
so the grain diameter using the hall-petch equation=3.115× [tex]10^{-3}[/tex] meter
