GATE 2025 MT – Question 61
A single-crystal BCC metal with lattice parameter $a=0.4$ nm deforms at shear strain rate $0.001\ \mathrm{s^{-1}}$. Its average mobile dislocation density is $10^{10}\ \mathrm{m^{-2}}$. The average dislocation velocity is ______ $\times10^{-3}\ \mathrm{m\,s^{-1}}$ (rounded to two decimal places). Given: Burgers vector $\mathbf b=(a/2)\langle111\rangle$.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 0.27 to 0.30
Explanation
The Burgers-vector magnitude is $b=a\sqrt3/2=0.346410\times10^{-9}$ m.
Orowan’s relation gives $\dot\gamma=\rho_mbv$, so $v=0.001/[10^{10}(0.346410\times10^{-9})]=2.88675\times10^{-4}$ m/s.
This is $0.288675\times10^{-3}$ m/s. The requested coefficient is **0.29**.