crystaldefects
- 1. CRYSATL DEFECTS INTRODUCTION .TYPES OF DEFECTS POINT DEFECT LINE DEFECT.AREA OR PLANAR DEFECT CONCLUSIONS
- 2. NAME : SIVAKANALI.S ROLL NO : 117011305043 DEPT : M.TECH(INT) II-yr. SUB :XGS407(TECHNICAL COMMUNICATION) ) .
- 3. INTRODUCTION An imperfection in a crystal’s lattice structure either a missing atom or ion creating vacancy in lattice or an extra atom or ion between two normal lattice points creating an interstitial.
- 4. CRYSATL DEFECTS 1.PERFECT ORDER doesn’t exist throughout a crystalline material on a atomic scale. 2.It influence properties such as MECHANICAL,ELECTRICAL, MAGNETIC 3.All crystalline materials contain large number of various defects or imperfection.
- 5. ONE DIMENSIONAL DEFECT Zero- Dimensional defect Two-Dimensional defects It is generally according to geometry or dimensionality of the defect. TYPES OF DEFECTS:
- 6. POINT DEFECT (0-D DEFECT) VACCANCY IMPURITY ATOMS *Substitutional. *Interstitial. EDGE DISLOCATION SCREW DISLOCATION LINE DEFECT (1-D DEFECT) GRAIN BOUNDARIES AREA DEFECT (2-D DEFECT) TWIN BOUNDARIES DEFECTS CONT…
- 7. VACCANCY Missing atom from an atomic site 1 2 • Atoms around vacancy displaced 3 • Tensile stress field produced in the vicitnity 4 • When temperature increases vacancy will be created
- 8. IMPURITY OF ATOMS INTERSTITIAL Foreign atom positioned between atomic site.(e.g) C in BCC iron. SUBSTITUTIONAL Foreign atom that substitutes for or replaces a parent atom in the crystal. Pentavalent or trivalent impurity atoms doped in Si or Ge are also substitutional impurities in a crystal.
- 9. LINE DEFECT_ DISLOCATION In early 1900’s scientist observed that metals undergo plastic deformation at forces much smaller than the forces that are holding the metal atoms together. they postulated that there are some defects(dislocations),which is bringing down the stress required for the plastic deformation.
- 10. DISLOCATIONS Many mettallurgists remained skeptical of the dislocation theory until the development of the transmission electron microscope (TEM) in the late 1950’s. TEM allowed experimental evidence to be collected that showed that the strength and ductility of the metals are con trolled by the dislocations.
- 11. Edge dislocations : E D G Extra half-plane of atoms is introduced midway through crystal Dislocation motions requires movement in baby steps. When force applied from one side of the crystal ,the extra plane passes through planes of atoms breaking and joining bonds with them until it reaches the grain boundary. Bond across the slipping planes are broken and remade in succession.
- 12. SCREW DISLOCATIONS: 1.A dislocation in the lattice structure of a crystal in which the atoms are arranged in a HELICAL PATTERNS that is normal to the direction of the stress . 2.It has no extra planes 3.The defects appears through part of the crystal has been cut in two, then shifted down on one side of the cut.
- 14. TWIN BOUNDARY The region between the pair Of boundaries is called “Twinned region” one boundary is restored by the 1 It is a special type of grain boundary across which there is MIRROR LATTICE. Twins do not extend beyond a grain boundary.
- 15. TWIN BOUNDARY cont….. ANNEALINGTWINS Twins which forms during the process of RECRYSTALLIZATION are called “Annealing twins” It is typically found in metals that have FCC crystal structure DEFORMATIONTWINS Twins which forms during the process of PLASTIC DEFORMATION are called “deformation twins” It is typically found in metals that have BCC and HCP crystal
- 16. CONCLUSION Crystals are like people, it is the defects in them which tend to make them interesting!!!!!