30 Years of Nanoindentation with the Oliver-Pharr Method and Beyond: Novel Methods
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Verena Maier-Kiener, Montanuniversitaet Leoben; Benoit Merle, University Of Kassel; Erik Herbert, Michigan Technological University; Samantha Lawrence, Los Alamos National Laboratory; Nigel Jennett, Coventry University
Wednesday 2:00 PM
March 2, 2022
Room: 259B
Location: Anaheim Convention Center
Session Chair: Daniel Gianola, University of California, Santa Barbara; Benoit Merle, University Of Kassel
2:00 PM Invited
Optimization of Segregation-engineered Nanocrystalline Al Alloys Using Nanomechanical Testing: Daniel Gianola1; 1University of California-Santa Barbara
Modern aluminum alloys have made great strides in ambient temperature performance and are amenable to advanced production routes such as additive manufacturing, but lack elevated temperature robustness where gains in efficiency can be obtained. We demonstrate the intentional design of disorder at interfaces in segregation-engineered ternary nanocrystalline alloys that exhibit exceptional thermal stability and elevated temperature strength. Combinatorial thin film depositions produce libraries from 4 ternary systems, enabling downselection of optimized compositions for bulk processing aided by rapid nanomechanical testing. Experiments point to synergistic co-segregation of alloying additions driving the evolution of amorphous intergranular films separating sub- 10 nm Al-rich grains, which gives rise to emergent thermal stability. We ascribe this intriguing behavior to near-equilibrium interface conditions followed by kinetically sluggish intermetallic precipitation in the confined disordered region. The resulting outstanding mechanical performance at high homologous temperatures lends credence to the efficacy of promoting disorder in alloy design and discovery.
2:25 PM
Using Machine Learning Approaches to Enable Insights in Nanoindentation Tip Wear: Claus Trost1; Stanislav Zak1; Sebastian Schaffer2; Megan Cordill1; 1Erich Schmid Institute of Materials Science; 2Wolfgang Pauli Institute, Faculty of Mathematics and University of Vienna Research Platform MMM Mathematics - Magnetism - Materials
Extraction of material mechanical behaviour exceeding the classical Oliver and Pharr analysis is a complex task. Therefore, different approaches such as machine learning algorithms are being used to interpret indentation data. In this study, different machine learning methods will be used on simulated 2D, 3D simulations to interpret nanoindentation experiments. The simulated data will be used to find features in indentation curves and train machine learning algorithms to predict both tip wear and material parameters. The direct interpretation of the wear is expected to give new insights in nanoindentation experiments. The machine learning methods will be analysed using the game theory-based model agnostic SHAP (Shapley Additive exPlanations) approach and light will be shed on the impact of different features on the output of the respective model. SHAP is expected to enhance the understanding of machine learning problems in the field of nanoindentation and many other areas.
2:45 PM
Correlation between Electrical Contact Resistance, Deviation from Elastic Unloading and Phase Transformation in Silicon: Ben Beake1; Tim Jochum1; 1Micro Materials Ltd.
Silicon undergoes complex behavior during indentation, with phase transformations and brittle fracture at higher load. The Oliver and Pharr method takes advantage of the fact that initial elastic unloading follows power-law behavior, so any deviation from this can be used to detect the onset of non-elastic deformation. Electrical contact resistance measurements using a Boron-doped diamond Berkovich indenter as the electrically conductive probe show that, for Si(100), this is associated with phase transformation during unloading which begins well before the well-known “pop-out” event. Initial deviation from elastic behavior was accompanied by a more rapid decrease in electrical current with subsequent pop-out accompanied by an abrupt increase in electrical current. These changes are consistent with Si-II initially transforming to a-Si and then to more electrically conductive high pressure phases such as Si-III/Si-XII.
3:05 PM
A Novel Nanoindentation Protocol to Characterize Surface Free Energy of Superhydrophobic Nanopatterned Materials: Edoardo Rossi1; Pardhasaradhi Sudharshan Phani2; Warren Oliver3; Marco Sebastiani1; 1Università degli Studi Roma Tre; 2International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI); 3KLA Corporation
The non-destructive measurement of surface free energy (SFE) in nano-patterned super-hydrophobic surfaces is challenging as the conventional contact angle measurements (CAMs) are often time-consuming and not feasible. In this work, a novel nanoindentation-based method will be presented to measure the pull-off adhesive forces by a combination of improved instrumentation capabilities (high precision electronics and controlled environment) and a robust test protocol that allows precise control of the interaction depths for implementing adhesion-accounting contact mechanics models.The new method is validated on carefully prepared reference surfaces such as highly energetic, atomically flat muscovite mica crystals and DSP (CZ) germanium <100> crystals. It was found to be capable of measuring SFE over five orders of magnitude, from hydrophilic to super-hydrophobic surfaces (produced by both patterning, fluorinate silane coating and their combination). CAM, wherever applicable, provided comparative data. Finally, the application of the method to understand surface functionalization processes will be presented.
3:25 PM Break
3:40 PM
A Multi-modal Mapping Approach to Enable Correlative Compositional, Crystallographic and Mechanical Property Analysis: Hazel Gardner1; Christopher Magazzeni1; Phillip Gopon2; Katharine Fox3; Michael Moody1; Paul Bagot1; David Armstrong1; 1University of Oxford; 2University of Leoben; 3Rolls-Royce plc
A correlative approach to microstructural mapping is presented, directly correlating mechanical properties data from nanoindentation with crystallographic data from Electron Backscattered Diffraction (EBSD) and compositional data from Electron Probe Microanalysis (EPMA). This is complemented by nanoscale compositional analysis through atom probe tomography (APT). Variations in mechanical response as a function of crystal orientation, composition and spatial position are measured using thousands of data points, rather than obtaining representative properties from smaller sample volumes. The approach is applied to a model titanium alloy and is also used to quantify the effect of oxygen ingress on the mechanical properties of an ex-service jet engine component. These case studies demonstrate the ability of the approach to rapidly obtain high-resolution data on structure-property relations from multi-component, industrially relevant systems.
4:00 PM
Your Default Load Function May be Working Against You and What To Do About It: Michael Maughan1; Evan Allen1; Marzyeh Moradi2; 1University of Idaho; 2KLA Corporation
Nanoindentation is commonly conducted using simple load functions with a single loading cycle. We investigate in a variety of pure metals a strict implementation of the Oliver-Pharr four-cycle load function and longer-hold load function for collecting indentation data and compare these to simple triangle load functions as commonly applied. The choice of load function is shown to impact the magnitude of hardness and indentation size effect (ISE) through low-temperature creep. In some cases, as much as 30% difference in hardness is observed. Nanoindentation testing strategies for best comparability between indentation depths are discussed in terms of microstructure mechanisms and practical testing techniques. A mechanism to account for the depth change based on Cottrell’s exhaustion creep is presented.