ISSUES TO ADDRESS...

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Part 8: DEFORMATION AND STRENGTHENING MECHANISMS ISSUES TO ADDRESS... • Why are separations watched basically in metals and compounds? • 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-pressed bearings for slip. electron cloud particle centers • Covalent Ceramics (Si, jewel): Motion hard. - directional (precise) holding • Ionic Ceramics (NaCl): Motion hard. - need to keep away from ++ and - neighbors. 2

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DISLOCATION MOTION Plastically extended zinc single gem. • Produces plastic disfigurement, • 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 separations don't move, disfigurement doesn't occur! Adjusted from Fig. 7.8, Callister 6e. 3

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INCREMENTAL SLIP • Dislocations slip planes incrementally ... • The separation line (the moving red dot)... ...isolates slipped material on the left from unslipped material on the privilege. Reenactment of disengagement movement from left to great precious stone is sheared. (Obligingness P.M. Anderson) 4

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BOND BREAKING AND REMAKING • Dislocation movement requires the progressive knocking of a half plane of molecules (from left to appropriate here). • Bonds over the slipping planes are softened and changed up progression. Nuclear perspective of edge disengagement movement from left to perfectly fine gem is sheared. (Obligingness P.M. Anderson) 5

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DISLOCATIONS & CRYSTAL STRUCTURE • Structure: close-pressed planes & headings are favored. see onto two close-stuffed planes. • Comparison among gem structures: FCC: some nearby pressed planes/bearings; HCP: just a single plane, 3 headings; BCC: none • Results of pliable testing. Mg (HCP) elastic heading Al (FCC) 6

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STRESS AND DISLOCATION MOTION • Crystals slip because of a settled shear push, t R . • Applied strain can create such an anxiety. slip plane ordinary, n s slip bearing slip course slip heading 7

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CRITICAL RESOLVED SHEAR STRESS • Condition for disengagement movement: • Crystal introduction can make it simple or difficult to move disl. 8

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DISL. Movement IN POLYCRYSTALS • Slip planes & headings ( l , f ) change starting with one gem then onto the next. • t R will differ starting with one gem then onto the next. • The precious stone with the biggest t R yields first. • Other (less positively situated) precious stones yield later. Adjusted from Fig. 7.10, Callister 6e. (Fig. 7.10 is graciousness of C. Brady, National Bureau of Standards [now the National Institute of Standards and Technology, Gaithersburg, MD].) 300 m 9

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4 STRATEGIES FOR STRENGTHENING: 1: REDUCE GRAIN SIZE • Grain limits are boundaries to slip. • Barrier "strength" increments with misorientation. • Smaller grain measure: more boundaries 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.) 10

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GRAIN SIZE STRENGTHENING: AN EXAMPLE • 70wt%Cu-30wt%Zn metal compound • 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 kindness of J.E. Burke, General Electric Co. 11

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ANISOTROPY IN s yield • Can be incited 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 heading 235 m - isotropic since grains are approx. round & haphazardly arranged. - anisotropic since moving influences grain introduction and shape. 12

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ANISOTROPY IN DEFORMATION 1. Barrel of Tantalum machined from a moved plate: 2. Fire chamber at an objective. 3. Disfigured barrel Photos kindness 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. 13

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STRENGTHENING STRATEGY 2: SOLID SOLUTIONS • Impurity iotas mutilate the cross section & create push. • Stress can deliver a boundary to separation 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. 14

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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. 15

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

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DISLOCATIONS DURING COLD WORK • Ti compound after frosty working: • Dislocations ensnare with each other amid chilly work . • Dislocation movement turns out to be more troublesome. Adjusted from Fig. 4.6, Callister 6e. (Fig. 4.6 is obligingness 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 disfigured example: r d ~ 10 mm/mm 3 • Ways of measuring disengagement thickness: 40 m Micrograph adjusted from Fig. 7.0, Callister 6e. (Fig. 7.0 is obligingness of W.G. Johnson, General Electric Co.) OR • Yield push increments as r d builds: 18

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SIMULATION: DISLOCATION MOTION/GENERATION • Tensile stacking (even dir.) of a FCC metal with indents in the top and base surface. • Over 1 billion iotas displayed in 3D square. • Note the vast increment in disl. thickness. Recreation graciousness of Farid Abraham . Utilized with consent from International Business Machines Corporation. Tap on picture to vivify 19

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DISLOCATION-DISLOCATION TRAPPING • Dislocation produce push. • This traps different separations. 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 frosty 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 separations past hindrances. 23

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EFFECT OF HEATING AFTER %CW • 1 hour treatment at T temper ... diminishes TS and builds %EL. • Effects of icy work are switched! • 3 Annealing stages to examine... 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 precious stones are shaped that: - have a little disl. thickness - are little - expend frosty worked gems. 0.6 mm 0.6 mm Adapted from Fig. 7.19 (a),(b), Callister 6e. (Fig. 7.19 (a),(b) are civility of J.E. Burke, General Electric Company.) 33% chilly worked metal New precious stones nucleate after 3 sec. at 580C. 26

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FURTHER RECRYSTALLIZATION • All icy 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 expend littler ones. • Why? Grain limit region (and in this way vitality) is diminished. 0.6 mm 0.6 mm Adapted from Fig. 7.19 (d),(e), Callister 6e. (Fig. 7.19 (d),(e) are civility of J.E. Burke, General Electric Company.) After 8 s, 580C After 15 min, 580C coefficient reliant on material and T. • Empirical Relation: type typ. ~ 2 slipped by time grain diam. at time t. 28

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TENSILE RESPONSE: BRITTLE & PLASTIC Stress-s

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