HW7 F10 Solutions - ENMA 300: Solutions Set #7 Dislocations...

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Page 1 of 2 ENMA 300: Solutions Set #7 Dislocations 1. A metal crystal has a Burgers vector of length 0.272nm. If the lattice parameter a is 0.314, is the metal crystal structure FCC or BCC? The Burgers vector is ( a /2)*[110] in FCC structures and ( a /2)*[111] in BCC structures, where [xyz] donates a vector of length x 2 +y 2 +z 2 along the [xyz] crystal direction. Their lengths are sqrt(2) a /2 and sqrt(3) a /2, respectively. 0.272 = sqrt(3)*0.314/2. It is a BCC. 2. In a simple cubic crystal with lattice parameter of 0.25nm, a tilt boundary is formed with an angle of 2.5º. What is the concentration of dislocations in the tilt boundary? Each edge dislocation adds one lattice parameter to the width of the material. tan( α ) = width of tilt boundary / length of tilt boundary = 0.25 * number of dislocations / length of tilt boundary = 0.25 * conc. of dislocations conc. of dislocation = tan(2.5º)/0.25 = 0.175 per nm. Note: Instead of tan(
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This note was uploaded on 08/02/2011 for the course ENMA 300 taught by Professor Alsheikhly during the Spring '11 term at University of Maryland Baltimore.

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HW7 F10 Solutions - ENMA 300: Solutions Set #7 Dislocations...

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