Nanomechanical Testing

Nanomechanical Testing Journal Club

Keep apprised of recent research with nanomechanical test instruments

We regularly come across interesting and informative materials research articles. Members of our Nanomechanical Testing Journal Club receive brief reviews of select papers and direct links to the full article. Our Journal Club is meant to be a helpful tool that keeps you up-to-date on the newest in Nanomechanical Testing research and to assist you in discovering articles you may have missed.

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Highly Ductile Amorphous Oxide at Room Temperature and High Strain Rate

Oxide glasses are an integral part of the modern world, but their usefulness can be limited by their characteristic brittleness at room temperature. We show that amorphous aluminum oxide can permanently deform without fracture at room temperature and high strain rate by a viscous creep mechanism. These thin-films can reach flow stress at room temperature and can flow plastically up to a total elongation of 100%, provided that the material is dense and free of geometrical flaws. Our study demonstrates a much higher ductility for an amorphous oxide at low temperature than previous observations. This discovery may facilitate the realization of damage-tolerant glass materials that contribute in new ways, with the potential to improve the mechanical resistance and reliability of applications such as electronic devices and batteries.

 

Erkka J. Frankberg, Janne Kalikka, Francisco García Ferré, Lucile Joly-Pottuz, Turkka Salminen, Jouko Hintikka, Mikko Hokka, Siddardha Koneti, Thierry Douillard, Bérangère Le Saint, Patrice Kreiml, Megan J. Cordill, Thierry Epicier, Douglas Stauffer, Matteo Vanazzi, Lucian Roiban, Jaakko Akola, Fabio Di Fonzo, Erkki Levänen, Karine Masenelli-Varlot

Science, 2019, 366 (6467), 864-69
DOI: 10.10.1126/science.aav1254

High-Throughput Nanoindentation for Statistical and Spatial Property Determination

Standard nanoindentation tests are “high throughput” compared to nearly all other mechanical tests, such as tension or compression. However, the typical rates of tens of tests per hour can be significantly improved. These higher testing rates enable otherwise impractical studies requiring several thousands of indents, such as high-resolution property mapping and detailed statistical studies. However, care must be taken to avoid systematic errors in the measurement, including choosing of the indentation depth/spacing to avoid overlap of plastic zones, pileup, and influence of neighboring microstructural features in the material being tested. Furthermore, since fast loading rates are required, the strain rate sensitivity must also be considered. A review of these effects is given, with the emphasis placed on making complimentary standard nanoindentation measurements to address these issues. Experimental applications of the technique, including mapping of welds, microstructures, and composites with varying length scales, along with studying the effect of surface roughness on nominally homogeneous specimens, will be presented.

 

Eric Hintsala, Ude Hangen, Douglas D. Stauffer

Journal of Materials, 2018, 70 (4), 494-503
DOI: 10.1007/s11837-018-2752-0

Bioinspired Nacre-like Alumina with a Bulk-metallic Glass-forming Alloy as a Compliant Phase

Bioinspired ceramics with micron-scale ceramic “bricks” bonded by a metallic “mortar” are projected to result in higher strength and toughness ceramics, but their processing is challenging as metals do not typically wet ceramics. To resolve this issue, we made alumina structures using rapid pressureless infiltration of a zirconium-based bulk-metallic glass mortar that reactively wets the surface of freeze-cast alumina preforms. The mechanical properties of the resulting Al2O3 with a glass-forming compliant-phase change with infiltration temperature and ceramic content, leading to a trade-off between flexural strength (varying from 89 to 800 MPa) and fracture toughness (varying from 4 to more than 9 MPa·m½). The high toughness levels are attributed to brick pull-out and crack deflection along the ceramic/metal interfaces. Since these mechanisms are enabled by interfacial failure rather than failure within the metallic mortar, the potential for optimizing these bioinspired materials for damage tolerance has still not been fully realized.

 

Amy Wat, Je In Lee, Chae Woo Ryu, Bernd Gludovatz, Jinyeon Kim, Antoni P. Tomsia, Takehiko Ishikawa, Julianna Schmitz, Andreas Meyer, Markus Alfreider, Daniel Kiener, Eun Soo Park, Robert O'Ritchie

Nature Communications, 2019, 10 (961)
DOI: 10.1038/s41467-008753-6

In Situ TEM Observation of Rebonding on Fractured Silicon Carbide

BioSilicon carbide (SiC) is widely used in harsh environments and under extreme conditions, including at high-power, high-temperature, high-current, high-voltage and high-frequency. The rebonding and self-matching of stack faults (SFs) is highly desirable to avoid catastrophic failure for SiC devices, especially for specific applications in the aerospace and nuclear power industries. In this study, a novel approach was developed using an eyebrow hair to pick up and transfer nanowires (NWs), in order to obtain in situ transmission electron microscope (TEM) images of the rebonding and self-matching of SFs at atomic resolution. During rebonding and healing, the electron beam was shut off. Rebonding on the fractured surfaces of monocrystalline and amorphous SiC NWs was observed by in situ TEM at room temperature. The fracture strength was 1.7 GPa after crack-healing, restoring 12.9% of that of a single crystal NW. Partial recrystallization along the <111> orientation and the self-matching of SFs are responsible for the rebonding of the monocrystalline NW. In comparison, the fracture strengths were 6.7 and 5.5 GPa for the first and second rebonding, respectively recovering 67% and 55% of that of an amorphous NW. Atomic diffusion contributed enormously to the rebonding on fractured surfaces of an amorphous NW, resulting in a healed surface consisting of an amorphous phase and crystallites. This rebonding function provides new insight into the fabrication of high-performance SiC devices for the aerospace, optoelectronic and semiconductor industries.

 

Zhenyu Zhang, Junfeng Cui, Bo Wang, Haiyue Jiang, Guoxin Chen, Jinhong Yu, Chengte Lin, Chun Tang, Alexander Hartmaier, Junjie Zhang, Jun Luo, Andreas Rosenkranz, Nan Jiang, Dongming, Guo

Nanoscale, 2018, 10, 6261-69
DOI: 10.10.1039/C8NR00341F

Revealing the Relation Between Microstructural Heterogeneities and Local Mechanical Properties of Complex-Phase Steel by Correlative Electron Microscopy and Nanoindentation Characterization

In this Materials and Design article, the authors characterize the compositional and microstructural heterogeneity of a commercial complex-phase steel (CP800) by combining various electron microscopy techniques and nanoindentation. They use Bruker's XPM (accelerated property mapping) mode to obtain high-resolution hardness maps. A cube-corner indenter and micro-newton load were applied to limit the indent depth and spacing between adjacent indents to the nanometer scale. The resulting high-resolution hardness map is obtained and successfully overlapped with EPMA and EBSD results, based on which the correlation between compositional heterogeneity and hardness variation in complex-phase microstructure can successfully established.

In materials science the measured mechanical properties and the materials microstructure are closely linked. EPMA and EBSD are allowing insights into the local chemical composition and materials texture with evermore increased spatial resolution and have given an indication that the local properties of CP800 will be varying.

For the first time, a hardness map quantifies these local changes at highest resolution and demonstrates the close link between local chemistry, dislocation density, grain orientation of matrix, and precipitates the development of mechanical properties in adjacent grains or phases at the sub-µm level.

Yuling Chang, Mingxuan Lin, Ude Hangen, Silvia Richter, Christian Haase & Wolfgang Bleck

Materials and Design 203 (2021) 109620
DOI: 10.1016/j.matdes.2021.109620