DislocationBasics_General

DislocationBasics_General - Eocwixiwvg ( .. ’Kxjggamwwfi...

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Unformatted text preview: Eocwixiwvg ( .. ’Kxjggamwwfi aré Arm "pa/401% paw ,2“ afiw Vim } (WI-e: 6175.390? 719 060‘“ a”! $746!»)?! Ammé 1&5; gm ,afé flame Jami;ng 57%;; géygkg “in W ,giwgéwwéwfic éfiguzfiébe . . 74,; AW, m flmsa/M A w% M 7% Egg/W! 0% j fig}; 7%.} 1M: slaw ca WM can/[2' may! 24/3471. GéS/meix'qL’ W52] 9054 50749;?!) .. kl‘WEr/V} (WW/7 Ian?“ a? if ’_7”\ M $9.01 M“ 5,9135% ,nggf TIM'M oL'rwwsr'w :27? Moém-fimmflmx iD/‘s [om/14: on AM? 0‘1 (m Ibl-Om; Ly ,1. < (a) A dislocation loop. (b) Offset produced by action of shear stress 1- upon loop shown in (a). [V [H Positive sense along line Top view of a square dislocation loop. [ [do km 4 [49143 J (BI/(NEW) firm/9% é ; F5 w-b fmformd I'm (rang UVJM #5 0d3l0€¢¢¢7£fit "/‘m (2er 742 aWZr/fi age:de whom/)- #m v‘iv. zfm’W aka/“)5 A} wa "L a [4174} flaw» W W Mm as 5w c . SF / EH “‘75 pa/VlwmA flu} «Page Can/9% :49 “(wing 5&8th : r , ‘ -. f ‘ I f“ . ’ I Wald/Vt {/WVCLI/JéyT CZI‘£L¢.4,* lJ Q’AAIf‘éa‘fl‘fé‘rfz‘UZ/ 3/21 75(4’, ’36?{,»("’ ‘ . l J , r7 . A: ; . Q (3/ '7 {ht-{P {7.3; -. j > 3 .3. f ‘_ 2} s 15:35»; 3%)}: (a) ta. , FS/RH Burgers circuits in (a) a real crystal and (b) a perfect reference crystal. 5 points into the paper. ~ (5) _ _ , SF! RH Burgers circuits in (a) a perfect reference crystal and (b) a real crystal. {5 points into the paper. Dislocations: Line Defects That Cause Deformation Of C Wstais TO Occur At S Less Than The Theoretical Limits tresses duuum smdpoin't (La ignoring Lhc uoms) Ind 03) An edge Jamaica. (21) viewed from A con snowing the positions at the “cm: ncnr the dislocation. I l l I l Three—dimensional symbol f Two —dimensiona! symbols Elevation l Ptan l ‘ b l x l l b l b Dislocation ‘gude‘ __.—-r ___r diwion b l ..—p- ___ b st. I st plane ‘P e9 .o—T ‘f—‘f “ .dlslq‘ouflon que plane . Edge-dislocation conventions. The “carpet-ruck“ analogy of an edge dislocation- (B) Positive climb of an edge dislocation. Negative climb of an edge dislocation. (A) we Oiibl‘l‘b (a) UFfSKY‘b (4') (u) Macroscopic deformation. from edge dislocation glide. (b) Mac- roscopic dcfurmzuinn from screw dislncation glide. (c) Macroscopic deformation from edge dislocation climb. (From Ref. 9. used with permission of R. dc Wit.) . . - . . _ c We now summarize some of the more Significant properties of the edg i dislocation. 1 The edge dislocation may be vistxalizcd as an extra half-plane:- of atoms. ' " ‘ ' ' I he dislocation line. »-: 2. The Burgers vector is perpendicular to t I ‘ I, 3 The glide plane is defined by the dislocation line and the Burgers vector. _ _ 4 Glide motion causes the atoms above the glide plane to be displaced one Burgers vector relative to atoms below the glide plane. 1 § Climb motion occurs when the size of the extra half—plane changes, and it is accompanied by vacancy generation or annihilation. «xi-m“: We now list some properties of the screw dislocation that help on??? £~ A "E understand its nature. - jfiC‘ . . . _ _ l. T he Burgers vector is parallel to the dislocation line. Hen cc. sp taciny7 .— ing both the line and the [7 vector does not specify the glide pl for an edge dislocation. if 2. Glide motion causes the dislocation line to move at right angles to the.- glide direction. Therefore. the motion of the line is at right angles to both? the stress vector and the slip produced by the stress. 3. There is no way to visualize this dislocation as an extra plane of. atoms. ane as it does? @132. '1‘ '.i. 4. Passage of the dislocation line causes a movement of the atoms acros‘s'j V the glide plane by one h vector relative to each other, i . _ - Wain J r'-—.-> ABM mue- : 24m gammy? .L‘céLT lam. 5‘ '9 dhfis lie/la .* - '- cam-fin? dw came ~ - H, flyibm§ oz 93/002799“ 7&0/7 [I 0) 74¢ We refiw it -& vote 54,2 War I 2% WW 5 ' w m eta-295m; . flex! 1.} 4, [2,54% Mféé? " - - ‘ 514g wag/2n ,é'm, 2% 4 ’64“- IA. 4f 5“: 7%} L: Amuse mag'ZDISPLACEME/f/I‘ Raul/E; I = 9X? $740 MMM W F firm/m CAM/(B C 1—7/6 SW0 = Screw oUJlacdigc/ls cauuevL 7b» > 0 => me am oémfi Sb (no! Cyuéiw’weozzh 77%: ééé - - < A i'_ 3‘ ' 29“”! 252M :- 9&9: ' ' ' m__4‘;~a flit ale-isiswia‘u' hm abs 1 -» 'QLM‘BLCAQS"! ' 31-1 3.; i a 5 § . ‘7’: ‘ ' ) i! I . i {E ...
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This note was uploaded on 01/07/2011 for the course MEMS Mems1054 taught by Professor Wiezorek during the Fall '10 term at Pittsburgh.

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DislocationBasics_General - Eocwixiwvg ( .. ’Kxjggamwwfi...

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