XPM: High Speed Nanoindentation and Mechanical Property Mapping. Eric Hintsala, Ph.D

Transcription

1 XPM: High Speed Nanoindentation and Mechanical Property Mapping Eric Hintsala, Ph.D

2 2 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 features and interfaces, incorporating statistics, high temperature mapping 4. Conclusions and Q&A

3 Transducer & Performech II Controller Core Technology Springs Center Electrode Outer Electrode Outer Electrode Capacitive displacement sensing Small inertia of moved parts <1 g Low intrinsic dampening Indenter 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 Transducer Stability Specs 0.1 nm displacement noise floor 20 nn force noise floor <0.05 nm/sec thermal drift *Specs Guaranteed On-Site* Enabling Technology for Ultra-Small Materials Research 10/05/2017 Bruker Confidential 3

4 4 Load, P 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 P max Elastic Modulus (E) Hardness (H) 00 h f A c S E h h r max c 2 Ac H P max A c Depth, h

5 5 XPM Technology in Brief Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

6 6 XPM Technology in Brief Piezo Scanner Transducer Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

7 7 XPM Technology in Brief Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

8 8 XPM Technology in Brief Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

9 9 XPM Technology in Brief Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

10 10 XPM Technology in Brief Available with the Hysitron TI 980 TriboIndenter Utilizes existing hardware with advanced software control How it works: Approach routine makes contact with the sample Electrostatic actuation to perform experiment and withdraw Between indents, piezo is moved to next position

11 11 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 ( pt/s)

12 12 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)

13 13 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)

14 14 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

15 15 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

16 16 Best Practices for Mapping Parameters: Indent Spacing Hardness effect based on tip shape and depth 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

17 17 Best Practices for Mapping Parameters: Indent Spacing No modulus effect from tip shape 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

18 18 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

19 19 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

20 20 Applications: Mapping Microstructural Features Searching for Hard Intermetallic Phases in 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 Ti - BMG Weld Zone Main applications is multiphase materials, weld interfaces, and composite materials

21 Multi-Scale Mapping in Laser Cladding 10/05/2017 Bruker Confidential 21

22 22 Multi-Scale Mapping in Laser Cladding 410L Clad 2.5 mm/laser Step

23 Multi-Scale Mapping in Laser Cladding Hardness (GPa) Stage Automation Map 10/05/2017 Bruker Confidential 23

24 24 Multi-Scale Mapping in Laser Cladding EBSD Boundary Map EBSD Inverse Pole Figure Map XPM Hardness Map Overlay

25 25 Railway Steel Welding Joint GPa Hardness IPF SPM SEM High hardness in martensitic islands at grain boundaries 60 µm Slight hardness variations within grains correlated with orientation and grain roughness

26 26 Railway Steel Welding Joint: Microhardness vs. XPM Grids What does statistics get you? 196 indent grids gives statistical data Welding Joint 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 Nanoindentation Grid 14x14 with 3µm spacing Vickers Indentation

27 27 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?

28 28 Fine Microstructure Mapping xprobe XPM 0.1 μm Resolution (same as EBSD) The xprobe transducer is MEMS-based, with much improved load and displacement noise floor (2 nn, nm) Design is optimized for shallow indents, ultra thin films and other delicate measurements Tip This is the highest resolution demonstration available for XPM capabilities, with 100 nm indent spacing and 100 μn load

29 29 Fine Microstructure Mapping xprobe XPM 0.1 μm Resolution (same as EBSD) EBSD Phase Map EBSD Inverse Pole Figure Map XPM Hardness Map

30 30 SiC Fiber-Matrix Composite 10/05/2017 Schematic view of the Bruker xsolconfidential High Temperature Stage 30

31 31 SiC Fiber-Matrix Composite Fiber Matrix 400 C 10/05/2017 Bruker Confidential 31

32 32 SiC Fiber-Matrix Composite 10/05/2017 Bruker Confidential 32

33 33 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 SiO 2 layer below on properties Intrinsic thin film (I TF ) fitting yields the correct 182 GPa modulus for the Ta. Hardness drop is slow and constant as expected

34 34 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 SiO 2 layer below on properties Intrinsic thin film (I TF ) fitting yields the correct 182 GPa modulus for the Ta. Hardness drop is slow and constant as expected 10/05/2017 Bruker Confidential 34

35 35 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 SiO 2 layer below on properties Intrinsic thin film (I TF ) fitting yields the correct 182 GPa modulus for the Ta. Hardness drop is slow and constant as expected 10/05/2017 Bruker Confidential 35

36 36 Exciting Future Applications Combinatorial materials studies Rough thin films Cross-sectioned materials with damage gradients (radiation, corrosion, etc.) Continuous temperature ramping Humidity or other environmental gas ramping Bruker Confidential 36

37 37 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 Bruker Confidential 37 single standard nanoindents. Similarly, strain rate sensitivity should be considered and explored through loading rate variation experiments.

38 38 Thank You! Q & A Session Further questions? Contact me at: eric.hintsala@bruker.com Bruker Confidential 38

39 39 References Nanoindentation Fundamentals Indentation Elastic-Plastic Zones/Size Effect Indentation Strain Rate Fischer-Cripps, A.C., Introduction to contact mechanics (p. 87). New York: Springer. Oliver, W.C. and Pharr, G.M., An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. Journal of materials research, 7(6), pp Nix, W.D. and Gao, H., Indentation size effects in crystalline materials: a law for strain gradient plasticity. Journal of the Mechanics and Physics of Solids, 46(3), pp Swadener, J.G., George, E.P. and Pharr, G.M., The correlation of the indentation size effect measured with indenters of various shapes. Journal of the Mechanics and Physics of Solids, 50(4), pp Hangen, U.D., Stauffer, D.D. and Asif, S.S., Resolution limits of nanoindentation testing. In Nanomechanical Analysis of High Performance Materials (pp ). Springer Netherlands. Schwaiger, R., Moser, B., Dao, M., Chollacoop, N. and Suresh, S., Some critical experiments on the strain-rate sensitivity of nanocrystalline nickel. Acta materialia, 51(17), pp Wei, Q., Cheng, S., Ramesh, K.T. and Ma, E., 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