Two parallel edge dislocations of the same sign glide on parallel slip planes in aluminium

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction

Solid State Physics, Ch Point defects, dislocations and alloys

Problem

Two parallel edge dislocations of the same sign glide on parallel slip planes in aluminium, separated by

d=500\,\mathrm{nm}

. Aluminium has shear modulus

G=26\,\mathrm{GPa}

and Burgers vector magnitude

b=2.86\,\mathrm{\AA}

(fcc, lattice constant

a=4.05\,\mathrm{\AA}

b=a/\sqrt2

). Using the order-of-magnitude interaction force per unit length

F/L\approx\frac{Gb^2}{2\pi d}

(dropping the angular and

(1-\nu)

factors that enter the exact edge-dislocation result), estimate: ((a)) the force per unit length between the two dislocations; ((b)) the equivalent shear stress

\tau=(F/L)/b

this represents, as a fraction of

G

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