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