ISSUES TO ADDRESS...

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Section 7: DISLOCATIONS AND STRENGTHENING ISSUES TO ADDRESS... • Why are separations watched principally in metals and amalgams? • How are quality and separation movement related? • How would we expand quality? • How can warming change quality and different properties? 1

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DISLOCATIONS & MATERIALS CLASSES • Metals: Disl. movement less demanding. - non-directional holding - close-stuffed headings for slip. electron cloud particle centers • Covalent Ceramics (Si, jewel): Motion hard. - directional (rakish) holding • Ionic Ceramics (NaCl): Motion hard. - need to keep away from ++ and - neighbors. 2

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DISLOCATION MOTION Plastically extended zinc single precious stone. • Produces plastic misshapening, • Depends on incrementally breaking bonds. Adjusted from Fig. 7.9, Callister 6e. (Fig. 7.9 is from C.F. Elam, The Distortion of Metal Crystals , Oxford University Press, London, 1935.) Adapted from Fig. 7.1, Callister 6e. (Fig. 7.1 is adjusted from A.G. Fellow, Essentials of Materials Science , McGraw-Hill Book Company, New York, 1976. p. 153.) • If disengagements don't move, disfigurement doesn't occur! Adjusted from Fig. 7.8, Callister 6e. 3

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STRESS AND DISLOCATION MOTION • Crystals slip because of a settled shear stretch, t R . • Applied strain can create such an anxiety. slip plane ordinary, n s slip heading slip course slip bearing 4

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CRITICAL RESOLVED SHEAR STRESS • Condition for separation movement: • Crystal introduction can make it simple or difficult to move disl. 5

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DISL. Movement IN POLYCRYSTALS • Slip planes & headings ( l , f ) change starting with one precious stone then onto the next. • t R will change starting with one precious stone then onto the next. • The precious stone with the biggest t R yields first. • Other (less positively arranged) precious stones yield later. Adjusted from Fig. 7.10, Callister 6e. (Fig. 7.10 is kindness of C. Brady, National Bureau of Standards [now the National Institute of Standards and Technology, Gaithersburg, MD].) 300 m 6

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4 STRATEGIES FOR STRENGTHENING: 1: REDUCE GRAIN SIZE • Grain limits are obstructions to slip. • Barrier "strength" increments with misorientation. • Smaller grain estimate: more obstructions to slip. • Hall-Petch Equation: Adapted from Fig. 7.12, Callister 6e. (Fig. 7.12 is from A Textbook of Materials Technology , by Van Vlack, Pearson Education, Inc., Upper Saddle River, NJ.) 7

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GRAIN SIZE STRENGTHENING: AN EXAMPLE • 70wt%Cu-30wt%Zn metal amalgam • Data: Adapted from Fig. 7.13, Callister 6e. (Fig. 7.13 is adjusted from H. Suzuki, "The Relation Between the Structure and Mechanical Properties of Metals", Vol. II, National Physical Laboratory Symposium No. 15, 1963, p. 524.) 0.75mm Adapted from Fig. 4.11(c), Callister 6e. (Fig. 4.11(c) is civility of J.E. Burke, General Electric Co. 8

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ANISOTROPY IN s yield • Can be instigated by rolling a polycrystalline metal - before moving - in the wake of moving Adapted from Fig. 7.11, Callister 6e. (Fig. 7.11 is from W.G. Moffatt, G.W. Pearsall, and J. Wulff, The Structure and Properties of Materials , Vol. I, Structure , p. 140, John Wiley and Sons, New York, 1964.) moving bearing 235 m - isotropic since grains are approx. circular & arbitrarily situated. - anisotropic since moving influences grain introduction and shape. 9

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ANISOTROPY IN DEFORMATION 1. Barrel of Tantalum machined from a moved plate: 2. Fire barrel at an objective. 3. Distorted chamber Photos politeness of G.T. Dark III, Los Alamos National Labs. Utilized with consent. side view moving course plate thickness bearing end see • The noncircular end see appears: anisotropic misshapening of moved material. 10

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STRENGTHENING STRATEGY 2: SOLID SOLUTIONS • Impurity iotas contort the cross section & create stretch. • Stress can deliver an obstruction to disengagement movement. • Smaller substitutional polluting influence • Larger substitutional contamination Impurity produces neighborhood shear at An and B that contradicts disl movement to one side. Polluting influence produces neighborhood shear at C and D that restricts disl movement to one side. 11

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EX: SOLID SOLUTION STRENGTHENING IN COPPER • Tensile quality & yield quality increment w/wt% Ni. Adjusted from Fig. 7.14 (an) and (b), Callister 6e. • Empirical connection: • Alloying builds s y and TS. 12

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STRENGTHENING STRATEGY 3: PRECIPITATION STRENGTHENING • Hard encourages are hard to shear. Ex: Ceramics in metals (SiC in Iron or Aluminum). • Result: 13

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SIMULATION: PRECIPITATION STRENGTHENING • View onto slip plane of Nimonic PE16 • Precipitate volume part: 10% • Average encourage measure: 64 (b = 1 nuclear slip remove) Simulation graciousness of Volker Mohles, Institut für Materialphysik der Universitåt, Münster, Germany (http://www.uni-munster.de/physik/MP/mohles/). Utilized with consent. 14

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APPLICATION: PRECIPITATION STRENGTHENING 1.5 m • Internal wing structure on Boeing 767 Adapted from Fig. 11.0, Callister 5e. (Fig. 11.0 is obligingness of G.H. Narayanan and A.G. Mill operator, Boeing Commercial Airplane Company.) • Aluminum is fortified with hastens framed by alloying. Adjusted from Fig. 11.24, Callister 6e. (Fig. 11.24 is cordiality of G.H. Narayanan and A.G. Mill operator, Boeing Commercial Airplane Company.) 15

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STRENGTHENING STRATEGY 4: COLD WORK (%CW) • Room temperature twisting. • Common framing operations change the cross sectional zone: - Forging - Rolling Adapted from Fig. 11.7, Callister 6e. - Drawing - Extrusion 16

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DISLOCATIONS DURING COLD WORK • Ti amalgam after icy working: • Dislocations snare with each other amid icy work . • Dislocation movement turns out to be more troublesome. Adjusted from Fig. 4.6, Callister 6e. (Fig. 4.6 is kindness of M.R. Plichta, Michigan Technological University.) 17

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RESULT OF COLD WORK • Dislocation thickness ( r d ) goes up: Carefully arranged specimen: r d ~ 10 3 mm/mm 3 Heavily twisted example: r d ~ 10 mm/mm 3 • Ways of measuring separation thickness: 40 m Micrograph adjusted from Fig. 7.0, Callister 6e. (Fig. 7.0 is graciousness of W.G. Johnson, General Electric Co.) OR • Yield stretch increments as r d builds: 18

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SIMULATION: DISLOCATION MOTION/GENERATION • Tensile stacking (even dir.) of a FCC metal with scores in the top and base surface. • Over 1 billion iotas displayed in 3D square. • Note the substantial increment in disl. thickness. Reenactment affability of Farid Abraham . Utilized with authorization from International Business Machines Corporation. 19

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DISLOCATION-DISLOCATION TRAPPING • Dislocation create stretch. • This traps different disengagements. 20

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IMPACT OF COLD WORK • Yield quality ( s ) increments. • Tensile quality ( TS ) increments. • Ductility ( %EL or % AR ) diminishes. y Adapted from Fig. 7.18, Callister 6e. (Fig. 7.18 is from Metals Handbook: Properties and Selection: Iron and Steels , Vol. 1, ninth ed., B. Bardes (Ed.), American Society for Metals, 1978, p. 221.) 21

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COLD WORK ANALYSIS • What is the elasticity & flexibility after icy working? Adjusted from Fig. 7.17, Callister 6e. (Fig. 7.17 is adjusted from Metals Handbook: Properties and Selection: Iron and Steels , Vol. 1, ninth ed., B. Bardes (Ed.), American Society for Metals, 1978, p. 226; and Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals , Vol. 2, ninth ed., H. Pastry specialist (Managing Ed.), American Society for Metals, 1979, p. 276 and 327.) 22

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s - e BEHAVIOR VS TEMPERTURE • Results for polycrystalline iron: Adapted from Fig. 6.14, Callister 6e. • s y and TS diminish with expanding test temperature. • %EL increments with expanding test temperature. • Why? Opportunities help disengagements past obstructions. 23

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EFFECT OF HEATING AFTER %CW • 1 hour treatment at T toughen ... diminishes TS and expands %EL. • Effects of icy work are switched! • 3 Annealing stages to talk about... Adjusted from Fig. 7.20, Callister 6e. (Fig. 7.20 is adjusted from G. Sachs and K.R. van Horn, Practical Metallurgy, Applied Metallurgy, and the Industrial Processing of Ferrous and Nonferrous Metals and Alloys , American Society for Metals, 1940, p. 139.) 24

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RECOVERY Annihilation decreases disengagement thickness. • Scenario 1 • Scenario 2 25

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RECRYSTALLIZATION • New gems are shaped that: - have a little disl. thickness - are little - devour cool worked precious stones. 0.6 mm 0.6 mm Adapted from Fig. 7.19 (a),(b), Callister 6e. (Fig. 7.19 (a),(b) are graciousness of J.E. Burke, General Electric Company.) 33% icy worked metal New gems nucleate after 3 sec. at 580C. 26

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FURTHER RECRYSTALLIZATION • All frosty worked precious stones are expended. 0.6 mm 0.6 mm Adapted from Fig. 7.19 (c),(d), Callister 6e. (Fig. 7.19 (c),(d) are cordiality of J.E. Burke, General Electric Company.) After 8 seconds After 4 seconds 27

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GRAIN GROWTH • At longer circumstances, bigger grains devour littler ones. • Why? Grain limit territory (and along these lines vitality) is lessened. 0.6 mm 0.6 mm Adapted from Fig. 7.19 (d),(e), Callister 6e. (Fig. 7.19 (d),(e) are politeness of J.E. Burke, General Electric Company.) After 8 s, 580C After 15 min, 580C coefficient subject to material and T. • Empirical Relation: example typ. ~ 2 slipped by time grain diam. at time t. 28

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SUMMARY • Dislocations are watched fundamentally in metals and combinations. • Here, quality is expanded by making d

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