famu-fsu college of engineering department of mechanical engineering 1 orientation imaging...

1FAMU-FSU College of EngineeringDepartment of Mechanical Engineering

ORIENTATION IMAGING MICROSCOPY (OIM)

- SOME CASE STUDIES

EML 5930 (27-750)

Advanced Characterization and Microstructural Analysis

A. D. Rollett, P.N Kalu, D. Waryoba

Spring 2006


OUTLINE REVIEW OF OIM

CASE STUDIES

Development of Polishing Technique For OIM Study of

Heavily Deformed OFHC Copper

Recrystallization in Heavily Deformed OFHC Copper

Heavily Deformed Cu-Ag

Deformed and Annealed OFHC Copper

Deformed and Annealed Cu-Nb

Other Examples


INTRODCUTION TO OIM - Diffraction

Diffraction of inelastically scattered electrons by lattice planes (hkl) according to Bragg’s law:

Sections of a pair of Kossel cones form a pair of parallel straight Kikuchi lines on the flat phosphor screen.

For maximum intensity, the specimen surface is steeply tilted at an angle of 20°-30° from grazing incidence.


INTRODCUTION TO OIM - EBSP formation


INTRODCUTION TO OIM - Data acquisition


TECHNIQUE DEVELOPMENT



(a) OIM grain boundary map and (b) EBSD patterns

EBSPs from a sample prepared by standard metallographic technique: Polished




(b)(a)

EBSPs from a sample prepared by standard metallographic technique: Polished + etched




(b)(a)

EBSPs from a sample prepared by Novel technique - Polished + Etched + Polished


Image Quality

Image Quality

Confidence Index

Confidence Index



IPF of wire drawn OFHC copper deformed to = 3.2, obtained via (a) OIM and (b) X-ray diffraction techniques

CONCLUSIONS Polishing by the novel technique, which consists

of polishing+etching+polishing, produced high

quality EBSPs leading to excellent OIM image.

IPF from OIM were consistent with the IPF from

X-ray diffraction


Rex in HEAVILY DEFORMED OFHC COPPER



Optical micrograph showing microstructure after deformation to = 3.2, = 405 MPa. Arrows show pockets of recrystallized grains.

Microstructure

Optical micrograph showing microstructure after deformation to = 1.3, = 392 MPa. No recrystallization



OIM map showing grain orientations at (a) p = 2.3, UTS = 411.5 MPa, and (b) p = 3.2, UTS = 405 MPa. The lines represent high angle boundaries, with misorientation > 15o.

U

X

V

Y

W

DD

(b)(a)


1

10

1112

13

<313>85°{184}<-12 17 2>

<12-6>40°{-4-19}<-46-3>

<213>75°{-3 11 6}<-65-2>

<1-1-3>48°{-8713}<25-3>

<1-21>26°{-212}<-34-5>

<112>54°{-265}<-12 22 –7>

<-4-13>45°{1 11 18}<7 29 2>

<-1-12>60°{198}<12 23 2>

<1-1-1>64°{-201}<23-8>

<144>60°{-6 13 5}<-24-2>

<-1-15>56°{-2 14 23}<13 11 –1><-211>63°

{3-4 11}<6 10 3>

<112>65°

<-210>36°

<-210>32°

<133>65° <4-2-1>42° <313>66°

<-1-12>60°

<2-1-2>52°<2-1-1>65°

<2-1-3>55°



OIM map showing grain orientations after deformation to p = 3.6, UTS = 390.5 MPa.


Color Key


Sh/B in HEAVILY DEFORMED OFHC COPPER

1

2

OIM maps of a heavily drawn Cu ( = 3.2) showing regions of shear bands.

Shaded IQ map of a heavily drawn Cu ( = 3.2) showing regions of shear bands.


Rex in HEAVILY DEFORMED OFHC COPPER CONCLUSION

Three regions were identified: Low processing strain < 2.5: No recrystallization,

elongated structure.

Intermediate strain 2.5 < < 3.2: Nucleation of recrystallization, shear bands formation. Shear bands occurred in grains with S{123}<634> orientation, and were inclined at 54° to the drawing direction. Their misorientation was between 5°s10°.

High strain > 3.2: Extended recrystallization, recrystallized grains were mainly of Cube {001}<100> and S{123}<624> orientations.

OIM proved to be a viable tool in the study of heavily deformed materials.


HEAVILY DEFORMED Cu-Ag


Optical micrograph of a heavily drawn CuAg ( = 3.2) showing regions of shear bands.

Shaded IQ map of a heavily drawn CuAg ( = 3.2) showing regions of shear bands.

HEAVILY DEFORMED CuAg


HEAVILY DEFORMED Cu-Ag

1

2

OIM maps of a heavily drawn CuAg ( = 3.18) showing regions of shear bands. The Grain boundaries were constructed with a misorientation criteria of 15°.


DEFORMED AND ANNEALED OFHC COPPER


ANNEALED OFHC COPPER - Microstructure

(a) Optical micrograph of annealed Cu, p = 3.1, 350°C

(a) Optical micrograph of annealed Cu, p = 3.1, 750°C


ANNEALED OFHC COPPER

OIM tiled IPF map showing grain orientations for Cu wire drawn to a strain of 3.1 and annealed at 250°C for 1 hr.


Color Key


ANNEALED OFHC COPPER: OIM-IPF

(a) Deformed Cu, p = 2.3 (b) Deformed Cu, p = 3.1


(a) Annealed Cu, p = 3.1, 250°C (b) Annealed Cu, p = 3.1, 300°C

(c) Annealed Cu, p = 3.1, 500°C (d) Annealed Cu, p = 3.1, 750°C


DEFORMED AND ANNEALED Cu-Nb/Ti



SEM micrograph of a heavily drawn Cu-Nb ( = 3.2) annealed at 500°C.

SEM micrograph of a heavily drawn Cu-Nb ( = 3.2) showing elongated Cu and Nb phases.



Annealed CuNb, p = 3.1, 250°C

(Nb phase extracted)


Other Examples

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