ORIENTATION IMAGING MICROSCOPY (OIM) - SOME CASE STUDIES

FAMU-FSU College of EngineeringDepartment of Mechanical Engineering

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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


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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


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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.


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INTRODCUTION TO OIM - EBSP formation


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INTRODCUTION TO OIM - Data acquisition


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TECHNIQUE DEVELOPMENT


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

EBSPs from a sample prepared by standard metallographic technique: Polished


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(b)(a)

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


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(b)(a)

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


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Image Quality

Image Quality

Confidence Index

Confidence Index


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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


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Rex in HEAVILY DEFORMED OFHC COPPER


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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


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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)


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1112

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<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°


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


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Color Key


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Sh/B in HEAVILY DEFORMED OFHC COPPER

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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.


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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.


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HEAVILY DEFORMED Cu-Ag


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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


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HEAVILY DEFORMED Cu-Ag

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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°.


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DEFORMED AND ANNEALED OFHC COPPER


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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


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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.


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Color Key


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ANNEALED OFHC COPPER: OIM-IPF

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


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(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


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DEFORMED AND ANNEALED Cu-Nb/Ti


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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.


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Annealed CuNb, p = 3.1, 250°C

(Nb phase extracted)


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Other Examples


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ORIENTATION IMAGING MICROSCOPY (OIM) - SOME CASE STUDIES

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