mechanical properties of nanocomposite alloys presented by jennifer barrow goals: to study the...
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Mechanical Properties of Nanocomposite Alloyspresented by Jennifer Barrow
Goals:
To study the mechanical properties of NANOPERM and FINEMET alloys.
To prepare the materials for experiments at the NHMFL.
Methods Used:
Melt spinning, Calorimetry, Nanoindentation
Rapid Solidification ProcessingAmorphous Tape Wound Core
Magnetic properties are well known forFINEMET and NANOPERM
Mechanical properties are not.
-2500
-2000
-1500
-1000
-500
0
500
440 460 480 500 520 540 560 580 600
NANOPERM Recrystallization Using the DSC
2C/min: Tpeak=503.4C5C/min: Tpeak=516.3C10C/min: Tpeak=527.0C20C/min: Tpeak=536.7C40C/min: Tpeak=548.8C60C/min: Tpeak=556.3C
Hea
t F
low
/ G
ram
Temperature ( oC)
A. HsiaoCMU Ph.d Thesis
Nanocrystallization & Calorimetry
Background
~10 nm
Nanocrystallization on heating
Material has interesting soft magnetic properties
Composition:
NANOPERM Fe88Zr7B4Cu1 FINEMET Fe73.53Si16.07B6.43Cu1.09Nb2.88
Nanocrystallization reaction (primary):
NANOPERM AmorphousαFe+amorphous’ (amorphous’ being rich in B, Zr)
FINEMET AmorphousFeSi +amorphous’ (amorphous’ being rich in Nb, B)
Strengthening mechanisms
Dense Random Packing of Hard Spheres (DRPHS): Amorphous Structure
Smaller atom substituted interstitially (B) Larger atom substituted (Zr)
Crystalline periodicity:(Fe,Fe3Si or FeCo)
Atom substitution puts strain
on the crystal
structure
(Fe,Fe3Si or FeCobased glass)
NANOPERM Hardness Data
2% vol
38% vol
0% vol
19% vol
Unique hardness trend is due to strengthening mechanisms within the amorphous structure.
(interstitial or substitutional)
Nanoindenter setup
Other observations in hardness data
• Surface crystallization skews hardness data at beginning of Hardness vs. X curve (don’t have X = 0 at the surface)
•Strengthening mechanisms (interstitial and substitutional) are cause for general increase in hardness.
•Drop in hardness at large X is due to the fact that with increased crystallization, the material takes on mechanical properties of the softer nanocrystals
Future Work•Annealing samples to obtain X(t), or % composition vs. time and a complete TTT curve.
•Polishing samples in order to eliminate surface crystallization.
•Determining mechanical properties at large X
Acknowledgements
• Amy Hsiao’s Thesis
• Changyong Um
• Michael McHenry
• http://vulcan2.cwru.edu/classes/emse201/overheads/StreMech.pdf