1. CHAPTER 7: DISLOCATIONS AND STRENGTHENING EDGE DISLOCATIONS

2. SCREW DISLOCATIONS

3. CHARACTERISTICS OF DISLOCATIONS

4. SLIP SYSTEMS

5. SLIP IN SINGLE CRYSTALS Resolved Shear Stress

6. Example Problem Consider a single crystal of BCC iron oriented such that a tensile stress is applied along [010] direction. Compute the resolved shear stress along a (110) plane and in a [ 11] direction when a tensile stress of 52 MPa is applied

7. STRENGTHENING BY GRAIN SIZE REDUCTION

8. SOLID SOLUTION STRENGTHENING

10. COLD WORKING -Forging-Rolling -Extrusion-Drawing

11. COLD WORKING

12. New crystals are formed that: --have a small disl. density --are small --consume cold-worked crystals. 33% cold worked brass New crystals nucleate after 3 sec. at 580C. Fig. 7.19 (a),(b), Callister 6e. (Fig. 7.19 (a),(b) are courtesy of J.E. Burke, General Electric Company.) 0.6 mm RECRYSTALLIZATION

13. All cold-worked crystals are consumed. After 4 seconds After 8 seconds Fig. 7.19 (c),(d), Callister 6e. (Fig. 7.19 (c),(d) are courtesy of J.E. Burke, General Electric Company.) 0.6 mm FURTHER RECRYSTALLIZATION

14. GRAIN GROWTH Empirical Relation: After 8 s, 580C After 15 min, 580C elapsed time coefficient dependent on material and T. grain diam. at time t. exponent typ. ~ 2 0.6 mm Fig. 7.19 (d),(e), Callister 6e. (Fig. 7.19 (d),(e) are courtesy of J.E. Burke, General Electric Company.)