laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy Mechanics of Nano- and Micro- Materials Nanoindentation/Nanocompression Diana Courty, Ralph Spolenak Based on a Tutorial given by T. Buchheit, Sandia National Labs FS 2009 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 0. Introduction Nanoindentation: Mechanical test at the nanoscale Simple principle: A hard tip with a well defined geometry is pressed into the sample, while the evolution of the applied load and the displacement of the tip during loading and unloading is measured. Sample geometry: Thin films Lines, colloids, columns, … Mechanical properties: Hardness and Young’s modulus Yield strength (with adequate choice of tip and sample geometry) Diana Courty, D-MATL, [email protected] 2 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 0. Introduction Outline 1. Contact mechanics 2. Testing (quasistatic) 3. Analysis methods 4. Factors affecting nanoindentation test data 5. Other techniques in Nanoindentation fracture toughness dynamic methods … Diana Courty, D-MATL, [email protected] 3 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 1. Contact mechanics Elastic contact (Hertz) Diana Courty, D-MATL, [email protected] 4 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 1. Contact mechanics Geometrical similarity in pyramidal tips Diana Courty, D-MATL, [email protected] 5 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 1. Contact mechanics Elastic-plastic contact For the determination of hardness, the examined material must be plastically deformed Criterion of Hertz (1857-1894): An absolute value for hardness is the least value of pressure beneath a spherical indenter necessary to produce a permanent set at the center of the area of contact. Indent on Thin Gold Film (0.5 mm, polycrystalline, gradient picture) H ≈ CY with C ≈ 3 (for metals) and Y = yield stress (stress at which plastic yielding first occurs) Diana Courty, D-MATL, [email protected] 6 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Device Hysitron TriboIndenter XY staging system Top-down optics TriboScanner Stage, TriboScanner with Transducer and Optical Device - Tandem piezoelectric ceramic tube - Imaging of the surface Transducer assembly - Three-plate capacitive design - Maximum force: 10 mN - Maximum depth: 5 μm Pros and cons: - + automation easy - - bad optics Diana Courty, D-MATL, [email protected] 7 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Device CSM Ultra Nanoindenter (UNHT) XYZ staging system Top-down optics Transducer assembly - Active reference - Maximum force: 100 mN - Maximum depth: 50 μm Pros and cons: - + very good optics (microscope magnification from 200x to 4000x) - - automation more tedious, just one sample at a time Diana Courty, D-MATL, [email protected] 8 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Tip geometries Three-Sided Pyramidal Tips Berkovich - Standard for nanoindentation - Bulk materials and thin films greater than 100 nm thick Cube Corner - Ultra thin films, hard coatings Three-Sided Pyramidal Tips (Handbook of Nanotechnology, Spinger Verlag) - Light load scratching Cono-Spherical Tips Cone angle 60°, 90°, 120° Radius <3 µm: Soft polymers Radius >3 μm: Very soft polymers and biological samples Flat punch (special applications) Conical Tip (Tip Selection Guide, HYSITRON) Diana Courty, D-MATL, [email protected] 9 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Load functions (quasistatic) 1400 Load Function t me n se g 600 Open loop Feedback control ing Lo t 200 0 0 Modes of Operation en ad 400 eg Load rate or displacement rate (segment time) 800 gs Maximum force or maximum displacement Load (mN) Composed of segments din Hold time 1000 loa 1200 Un Loading Rate: 100 mN/sec 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Time (sec) O loop and load control mode - Load control - Displacement control Partial unload Scanning probe microscopy (SPM) Diana Courty, D-MATL, [email protected] Partial unload with 20 cycles 10 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Load-displacement curves I Idealized load-displacement curves for materials with a wide range of hardness and elastic properties. Load/Displacement Curves (Handbook of Nanotechnology, Spinger Verlag, 2004) Diana Courty, D-MATL, [email protected] 11 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy “Real” load-displacement curve showing pop-in events (discrete yielding events separated by elastic deformation (Corcoran et al.,1997)). Load [μN] 2. Testing Load-displacement curves II “Pop-in” Indentation Depth [nm] Load-displacement curve 8000 Load, P [mN] from partial unload mode showing material flowing during hold time. 1000 nm Au film 10000 6000 4000 2000 0 0 200 400 600 800 1000 Displacement, h [nm] Diana Courty, D-MATL, [email protected] 12 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 2. Testing Load-displacment curves III Diana Courty, D-MATL, [email protected] 13 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 3. Analysis Oliver-Pharr method f Diana Courty, D-MATL, [email protected] 14 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 3. Analysis Determination of hardness Diana Courty, D-MATL, [email protected] 15 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 3. Analysis Determination of Young‘s modulus Diana Courty, D-MATL, [email protected] 16 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich 3. Analysis Area function nanometallurgy A(h) h Diana Courty, D-MATL, [email protected] 17 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Indenter geometry Machine compliance* Thermal drift Creep Pile-up/sink-in* Indentation size effect* Surface roughness … Diana Courty, D-MATL, [email protected] 18 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Machine compliance Diana Courty, D-MATL, [email protected] 19 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data The effect of machine compliance Diana Courty, D-MATL, [email protected] 20 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Indentation pile-up or sink-in Pile-up Diana Courty, D-MATL, [email protected] 21 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data The effect of indentation pile-up Diana Courty, D-MATL, [email protected] 22 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Indentation size effect (ISE) Increased hardness with decreasing indentation depth Geometrically necessary dislocations in the form of circular dislocation loops Presence of dislocations → increase of the effective yield strength → H↑ Gao and Huang, Scripta Materialia 48 (2003) 113–118 Lu et al., Key Engineering Materials Vol. 312 (2006) pp 363-368 Diana Courty, D-MATL, [email protected] 23 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Impact of substrate Ideally indentations so small that there is no impact of the substrate (often not possible) Rule of thumb: 10% of film thickness if hardness is of interest Young’s modulus nearly always influenced by substrate Saha and Nix, Acta Materialia 50 (2002) 23–38 Diana Courty, D-MATL, [email protected] 24 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 4. Factors affecting nanoindentation test data Impact of substrate Saha and Nix, Acta Materialia 50 (2002) 23–38 Diana Courty, D-MATL, [email protected] 25 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Dynamic testing Fracture toughness Compression tests Constant strain rate, creep tests, adhesion experiments, … Diana Courty, D-MATL, [email protected] 26 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Quasistatic vs. Dynamic Testing Quasistatic testing and standard analysis 1400 Loading Rate: 100 mN/sec Quasistatic Testing 1200 t en gm t Lo en ad 400 eg ing gs se 600 din and biomaterials, exhibit time-dependent loa Viscoelastic materials, such as polymers 800 Un material behavior. Hold time 1000 Load (mN) techniques assume elastic-plastic 200 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Time (sec) properties. The analysis of the viscoelastic properties Dynamic Testing requires dynamic testing. Several mechanical properties can be measured as a continuous function of depth in a single indentation. → Dynamic testing can be used on most materials, including metals and ceramics! Diana Courty, D-MATL, [email protected] 27 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Dynamic Testing The Dynamic Mechanical Analysis (DMA) uses sine wave loading curves. HYSITRON offers three test types: Frequency test → strain-rate dependency of materials Variable load test → depth profiling Variable load amplitude test → determining the linear viscoelastic region (constant ratio of amplitude and mean load) The drive frequency ω can be defined in Sine Wave Loading Curves a range of 0.1 to 300 Hz. Diana Courty, D-MATL, [email protected] 28 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Dynamic Testing – Data Analysis Displacement amplitude Χ and phase shift δ of the of the displacement signal are measured (offset in time scale of the red viscoelastic curve compared to the green elastic curve) From the data Χ, δ and ω the stiffness of the contact S and the damping of the material Cs is calculated. Storage modulus Loss modulus Loss factor E E tan d = Sinusoidal Test: Applied force/displacement (elastic response, viscoelastic response) vs. time S 2 Ac Cs 2 Ac w Cs S Diana Courty, D-MATL, [email protected] 29 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Dynamic Testing - Example Thin polymer film with mineral platelets, ~400nm thick, on Si substrate Load-Displacement Data of Nanocomposite (Average curve from five load experiments.) Storage and Loss Modulus of Nanocomposite (Average curve from four load experiments.) Diana Courty, D-MATL, [email protected] 30 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Fracture toughness by indentation Diana Courty, D-MATL, [email protected] 31 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Compression tests Compression tests on small columns Uchic et al., 2004 Ni, Ni3Al-Ta and Ni superalloys Column diameter: 0.5 μm – 40 μm Transition from bulk to size limited behavior at ~42 μm Greer and Nix, 2005 Au columns <001> with a diameter of 0.3 μm – 7.5 μm Flow stress at 10% strain: 4.5 GPa (~0.03 GPa for bulk gold, theoretical strength: ~12 GPa) Dependence on the Yield Strength on d-½ for Ni3Al-Ta (Uchic et al., 2004) Diana Courty, D-MATL, [email protected] SEM Image of Ni Superalloy sample after testing (Uchic et al., 2004) 32 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation High temperature tests Getting material parameters at high T Problems: T difference between material and tip drift M.Wheeler et al. / Surface & Coatings Technology 254 (2014) 382–387 Diana Courty, D-MATL, [email protected] 33 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation High temperature tests M.Wheeler et al. / Surface & Coatings Technology 254 (2014) 382–387 Diana Courty, D-MATL, [email protected] 34 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Adhesion tests Alumina platelets in epoxy matrix Complex FIB (Focused Ion beam) preparation method Phd thesis, 2014, Matthias Schamel Diana Courty, D-MATL, [email protected] 35 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy Phd thesis, 2014, Matthias Schamel Diana Courty, D-MATL, [email protected] 36 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Adhesion tests (Cantilever-shear test) FIB fabrication U-shaped cut Undercut Deposit Polishing Mechanical testing with sharp indenter (Nanoindentation) Phd thesis, 2014, Matthias Schamel Diana Courty, D-MATL, [email protected] 37 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy Stage I: Elastic loading Stage II: Progressive debonding Stage III: Frictional sliding Phd thesis, 2014, Matthias Schamel Diana Courty, D-MATL, [email protected] 38 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Pull-out experiments Glass fibre reinforced plastics (about 10 µm diameter) Flatpunch used Challenges: - sample preparation - hitting the right spot Diana Courty, D-MATL, [email protected] 39 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Pull-out experiments Diana Courty, D-MATL, [email protected] 40 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Fracture resistance of hard coatings SiC crystal double cantilever beam Size effects of micro DCB compression: (a) yielding in smaller GaAs struts with slip bands (arrowed), while (b) larger struts remain elastic. Liu et al., Applied physics letters 102, 171907 (2013) Diana Courty, D-MATL, [email protected] 41 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy Cracking in micro DCBs made from (a) CrN coating and (b) CrAlN/ Si3N4 coating. Liu et al., Applied physics letters 102, 171907 (2013) Diana Courty, D-MATL, [email protected] 42 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Fracture resistance - Pillar cracking A novel pillar indentation splitting test for measuring fracture toughness of thin ceramic coatings (here TiN) Sebastiani et al., Philosophical Magazine, 2014 http://dx.doi.org/10.1080/14786435.2014.913110 Diana Courty, D-MATL, [email protected] 43 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Scratch testing Typical load profile Scratch on ZrO2 scanned with 2 D transducer Diana Courty, D-MATL, [email protected] 44 laboratory for Eidgenössische Technische Hochschule Zürich Swiss Federal Institute of Technology Zurich nanometallurgy 5. Other techniques in nanoindentation Hardness mapping Hysitron application note, 2014 900 indents, 2.5 µm apart lightly deformed (5%) polycrystalline copper specimen local hardness in the vicinity of the twin boundaries substantially higher than that of the surrounding matrix Diana Courty, D-MATL, [email protected] 45
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