analysis of grain boundary mobility in commercially pure copper and pure nickel
DESCRIPTION
Analysis of Grain Boundary Mobility in Commercially Pure Copper and Pure Nickel. Ana Erb Advisor: Professor A. D. Rollett. Interests & Goals. Mobility pertains to the movement of grain boundaries, dominated by solute. Solute present in commercial alloys affect the migration of the boundaries. - PowerPoint PPT PresentationTRANSCRIPT
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Analysis of Grain Boundary Mobility in Commercially Pure
Copperand Pure Nickel
Ana Erb
Advisor: Professor A. D. Rollett
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Interests & Goals• Mobility pertains to the movement of
grain boundaries, dominated by solute.
• Solute present in commercial alloys affect the migration of the boundaries.
• Boundary mobility controls recrystallization in alloys, which is of importance to industry.
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• Recrystallization: the formation of new, strain-free grain structure from that existing in cold worked metal.
The effects of annealing on metals: (a) cold work, (b) after recovery, (c) after recrystallization, and (d) after grain growth.
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ApproachEquation for grain boundary mobility:
MPV where, V is the velocity of the boundaries, M is the mobility of the boundaries, and P is the driving pressure for migration.
V M P
HardnessTest
Annealing & OIM(during recrystallization)
StoredEnergy
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Commercially Pure Copper
• Initial treatment– Anneal at 800°C for 20
hours– Roll to 30% reduction– Polish overnight on the
Vibromet – Scratch sample
perpendicular to the rolling direction
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Figure on the left is after initial treatment, scratch can be seen.
Figure on the right is after the second anneal (800°C for 2 hours), sample oxidized and scratch gone.
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Commercially Pure Copper• Twin boundaries observed
in copper samples.• Characterized as a 60°
rotation about <111> crystal direction.
• Used information from “Extracting Twins from Orientation Imaging Microscopy Scan Data,” Ryan J.Larson and Stuart I. Wright.
3 60°<111> (depicted in black) 111 Pole Figure for Copper Sample
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Pure Nickel
• Initial treatment– Anneal two samples at
1000°C for 30 minutes– Roll to 30% reduction– Electro-polish – Scratch sample
perpendicular to the rolling direction
• Second anneal– Anneal sample again after
first OIM scan– one sample at 900°C in
argon for 20 minutes– other sample at 700°C in
argon for 20 minutes
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Figure on the left is after initial treatment.
The sample was then annealed at 900°C for 20 minutes in an argon tube
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Figure on the left is after initial treatment.
The sample was then annealed at 700°C for 20 minutes in an argon tube.
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Nickel OIM Datagrain boundary number misorientation angle < > sigma
1 59.1 1 1 1 32 59.9 1 -1 1 33 37.9 1 0 1 94 59.7 1 1 -1 35 59.4 -1 1 1 36 47.4 -2 -1 3 -7 54.6 0 -7 -8 118 38.3 10 -6 3 -9 59.7 -1 -1 1 310 54.8 2 -2 3 -11 57.6 -7 5 -5 -12 38.1 8 2 -13 -
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MPV
G
GP
2
factortaylor
hardness
Shear Modulus
annealedtime
diametergbV
Solving For Mobility
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Calculated Mobility and Grain Boundary Diameters
gb # grain diameter (m) gb mobility (m2 s/kg)1 189.9 1.84E-072 385.3 3.73E-073 552.9 5.36E-074 278.3 2.70E-075 316.1 3.06E-076 522.2 5.06E-077 289.6 2.80E-078 186.1 1.80E-079 123.8 1.20E-0710 152.4 1.48E-0711 507.5 4.92E-0712 182.9 1.77E-07
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Future Work
• Take samples back to FAMU/FSU COE.
• Prepare more nickel samples, now knowing what temperature range to work on.
• Obtain more grain mobility data on both the commercially pure copper samples and pure nickel samples.
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Acknowledgements
• Dr. Anthony D. Rollett• Mitra Taheri• Jason Gruber• Herb Miller• Chaovoon Samuel Lim• Mohammed Haroon Alvi• Jennifer Barrow• Diego Laboy
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Reference
• Humphreys, F.J. and M. Hatherly Recrystallization and Related Annealing Phenomena. Elsevier Science Ltd. 1996.
• Kalu, Peter. Recrystallization and Grain Size Determination. PowerPoint Presentation, Fall 2003.
• Rollett, A.D. Grain Boundary Properties: Energy, Mobility. PowerPoint presentation, Spring 2003.
• Taheri, Mitra L. In-Situ Quantification of the Solute Effect on Mobility, Character and Driving Pressure of Grain Boundaries During Recrystallization in Aluminum Alloys. Carnegie Mellon University.
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More on Mobility
Two main categories of boundary types:
• Low angle grain boundaries– Migration in the LAGBs occur during recovery
• High angle grain boundaries– Migration in the HAGBs occur during
recrystallization
• Angle refers to the angle of rotation required to coincide the two lattices.
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Solutes & Mobility• Solutes tend to segregate to any
interface and lower the free energy of the system.
• For a boundary to move away from the segregated solute requires energy to be supplied.
• Mobility is also strongly sensitive to boundary type.
• High mobilities tend to be associated with CSL structures.
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Coincident Site Lattice(CSL)
• A CSL is when a finite fraction of lattice sites coincide between two lattices.
• The reciprocal of the ratio of CSL sites to lattice sites is denoted by .