Bruker Home | Bruker - XPM: High Speed Nanoindentation and ... · 5/10/2017 · 10/05/2017 Bruker Confidential 37 Bruker Confidential 37 1. XPM enables new techniques and studies

XPM: High Speed Nanoindentation and Mechanical Property Mapping

Eric Hintsala, Ph.D.2017-10-05

Table of Contents

1. Introduction: Brief overview of nanoindentation and nanomechanical property mapping

2. XPM™ Discussion: Pros/Cons of high speed mechanical property mapping and best practices for mapping parameters(speeds and spacing)

3. Applications Part: Mapping microstructural featuresand interfaces, incorporating statistics, high temperature mapping

4. Conclusions and Q&A

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Transducer & Performech II ControllerCore Technology

• Capacitive displacement sensing• Small inertia of moved parts <1 g• Low intrinsic dampening

Indenter

Center Electrode

Outer Electrode

Springs

Outer Electrode

Transducer Stability Specs

• 0.1 nm displacement noise floor

• 20 nN force noise floor

• <0.05 nm/sec thermal drift

*Specs Guaranteed On-Site*

• Load or Displacement Control • 78 kHz Feedback Loop Rate• 38 kHz Data Acquisition Rate• Experimental Noise Floor <100 nN (Digital Controller)• Enhanced Testing Routines• Digital Signal Processor (DSP) + Field Programmable

Gate Array (FPGA) + USB Architecture• Modular Design

Enabling Technology for Ultra-Small Materials Research

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Basic Nanoindentation Principles –Quasi-Static Nanoindentation

• Depth sensing technique– constant acquisition of load and depth

• Contact area fit using calibration against a standard sample – Variety of probe shapes can be used

• Main extracted properties – hardness and modulus


Depth, h

Lo

ad

, P

hf00

Pmax

hmaxhc

Ac

c

rA

SE

2

Elastic Modulus (E)

cA

PH max

Hardness (H)

XPM Technology in Brief

• Available with the Hysitron® TI 980 TriboIndenter®

• Utilizes existing hardware with advancedsoftware control

• How it works:

• Approach routine makes contact with the sample

• Electrostatic actuation to perform experimentand withdraw

• Between indents, piezo is moved to next position





• How it works:





Piezo Scanner

Transducer




• How it works:








• How it works:








• How it works:








• How it works:





XPM Load Functions


• Rectangular grids, can set spacing and number of indents

• Trapezoid load function only (default 0.1s load-hold-unload, can modify)

• Setpoint variation

• Can vary load linearly or by %

• Lateral move speed can be adjusted and translation protocol selected

• Limited by piezo scanner range (75 μm) and total number of data points (209715 pt/s)

XPM Analysis


• Input preload, number of segments (2 or 3)

• Analysis using parameters from the quasi subtab

• Quasi subtab allows selection of area function, fitting range, etc.

• Several plotting options,plus histograms and basic statistical analysis

• Automatically generate text file complete with positions(can plot in origin)

XPM Analysis


• Input preload, number of segments (2 or 3)

• Analysis using parameters from the quasi subtab

• Quasi subtab allows selection of area function, fitting range, etc.

• Several plotting options,plus histograms and basic statistical analysis

• Automatically generate text file complete with positions(can plot in origin)

Pros/Cons of High Speed Mechanical Property Mapping

• Pros: Speed (up to 6 indents/s) enables otherwise impractical activities

• Ability to map at high-resolutions

• Reduced effect of drift

• Gather statistical distributions quickly

• Can be coupled with stage automation (method)

• Compatible with xSol® heating stage

• Cons: Loss of some flexibility

• One approach for a whole grid (flat samples are best)

• Strain rate sensitive materials dictate caution

• Indent spacing will dictate indentation depth/load

• Limited to trapezoid load functions


Best Practices for Mapping Parameters:Indent Spacing


• The volume of material whose stress exceeds the yield strength is in the plastic zone – always smaller than the elastic zone

• Elastic properties (Modulus) are not affected by plastic deformation

• Size of plastic zone is dependent on load/depth, indenter geometry and the material being indented

• Indentation size effects result in changes in hardness over shallow depths

• Best solution is to compare with single quasi-static indents








Hardness effect based on tip shape and depth








No modulus effect from tip shape

Best Practices for Mapping Parameters:Indent Speed (Single Crystal Fe-3%Si example)

• Strain rate sensitivity is material specific

• A variety of loading rates should be tested on each sample

• Since this varies based on order of magnitude, nanoindentation probes a relatively narrow range of strain rates

• For this example, slight hardness effect at highest loading rate, no obvious modulus effect


Best Practices for Mapping Parameters:Indent Speed (Single Crystal Fe-3%Si example)


• Strain rate sensitivity is material specific

• A variety of loading rates should be tested on each sample

• Since this varies based on order of magnitude, nanoindentation probes a relatively narrow range of strain rates

• For this example, slight hardness effect at highest loading rate, no obvious modulus effect

Applications: Mapping Microstructural FeaturesSearching for Hard Intermetallic Phases in Weld Zone


Ti - BMG Weld Zone

• XPM mapping allows one to explore the properties of different microstructural features of specimens

• It is especially powerful when combined with supplementary structural characterization such as diffraction techniques to make structure property maps

• Main applications is multiphase materials, weld interfaces, and composite materials

Multi-Scale Mapping in Laser Cladding




410L Clad 2.5 mm/Laser Step



Hardness (GPa)

10

Stage Automation Map

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

2 3 4 5 6 7 8 9 10 11 12



EBSD Boundary Map EBSD Inverse Pole Figure Map XPM Hardness Map Overlay

Railway Steel Welding Joint


60 µ

m

Hardness IPF SPM SEM

• High hardness in martensitic islandsat grain boundaries

• Slight hardness variations within grains correlatedwith orientation and grain roughness

GPa

Railway Steel Welding Joint:Microhardness vs. XPM Grids


• 196 indent grids –gives statistical data

• XPM in red with error bars, microhardness in blue

• Better reproducibility in XPM, especially near the welding joint

• Data spread from martensite islands, grain boundaries

Individual XPM Grid

Welding Joint

Vickers

Indentation

Nanoindentation

Grid 14x14 with

3µm spacing

What does statistics get you?

Railway Steel Welding Joint:Microhardness vs. XPM Grids


• 196 indent grids –gives statistical data

• XPM in red with error bars, microhardness in blue

• Better reproducibility in XPM, especially near the welding joint

• Data spread from martensite islands, grain boundaries

What does statistics get you?

Fine Microstructure MappingxProbe™ XPM – 0.1 μm Resolution (same as EBSD)


• The xProbe transducer is MEMS-based, with much improved load and displacement noise floor (2 nN, 0.002 nm)

• Design is optimized for shallow indents, ultra thin films and other delicate measurements

• This is the highest resolution demonstration available for XPM capabilities, with 100 nm indent spacing and 100 μN load

Tip

Fine Microstructure MappingxProbe™ XPM – 0.1 μm Resolution (same as EBSD)


EBSD Phase Map EBSD Inverse Pole Figure Map XPM Hardness Map

SiC Fiber-Matrix Composite

10/05/2017 30Bruker Confidential10/05/2017 30Bruker Confidential

10/05/2017 30Bruker ConfidentialSchematic view of the xSol High Temperature Stage




Fiber Matrix 400°C




Ta Thin Film Temperature Ramp


• 36 indents per temperature• Speed limited by temperature

ramp ~ 5min per point to stabilize

• Modulus drop is minimal, theoretical change is ~3 GPa

• Influence of the SiO2 layer below on properties – Intrinsic thin film (ITF) fitting yields the correct 182 GPa modulus for the Ta.

• Hardness drop is slow and constant as expected

















Exciting Future Applications


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• Combinatorial materials studies

• Rough thin films

• Cross-sectioned materials with damage gradients(radiation, corrosion, etc.)

• Continuous temperature ramping

• Humidity or other environmental gas ramping

Summary



1. XPM enables new techniques and studies that are impractical with standard indentation.

2. The most ideal applications include high-resolution mapping of microstructure, statistical techniques, temperature ramping, and more.

3. Due to limited load function flexibility XPM is not a replacement for nanoindentation, but a fast way to evaluate inhomogeneities and quickly obtain statistically significant data sets.

4. One should choose indent spacings based upon load/depth. This is application specific and ideally should be tested by comparison with single standard nanoindents. Similarly, strain rate sensitivity should be considered and explored through loading rate variation experiments.

Thank You!



Q & A Session

Further questions?Contact me at: [email protected]

References


Nanoindentation Fundamentals

• Fischer-Cripps, A.C., 2000. Introduction to contact mechanics (p. 87). New York: Springer.

• Oliver, W.C. and Pharr, G.M., 1992. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. Journal of materials research, 7(6), pp.1564-1583.

Indentation Elastic-Plastic Zones/Size Effect

• Nix, W.D. and Gao, H., 1998. Indentation size effects in crystalline materials: a law for strain gradient plasticity. Journal of the Mechanics and Physics of Solids, 46(3), pp.411-425.

• Swadener, J.G., George, E.P. and Pharr, G.M., 2002. The correlation of the indentation size effect measured with indenters of various shapes. Journal of the Mechanics and Physics of Solids, 50(4), pp.681-694.

• Hangen, U.D., Stauffer, D.D. and Asif, S.S., 2014. Resolution limits of nanoindentation testing. In Nanomechanical Analysis of High Performance Materials (pp. 85-102). Springer Netherlands.

Indentation Strain Rate

• Schwaiger, R., Moser, B., Dao, M., Chollacoop, N. and Suresh, S., 2003. Some critical experiments on the strain-rate sensitivity of nanocrystalline nickel. Acta materialia, 51(17), pp.5159-5172.

• Wei, Q., Cheng, S., Ramesh, K.T. and

Ma, E., 2004. Effect of nanocrystalline

and ultrafine grain sizes on the strain

rate sensitivity and activation volume:

fcc versus bcc metals. Materials

Science and Engineering: A, 381(1),

pp.71-79.

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Bruker Home | Bruker - XPM: High Speed Nanoindentation and ... · 5/10/2017 · 10/05/2017 Bruker Confidential 37 Bruker Confidential 37 1. XPM enables new techniques and studies