Materials Science and Engineering Commons^™

Variable Temperature Ultra-Nanoindentation System: Elevated And Cryogenic Temperature Measurements, M. Conte, B. Bellaton, D. Ciani, N.X. Randall, P. Kempe, G. Moharty, J. Schwiedrzik, J. Michler

Nanomechanical Testing in Materials Research and Development V

One of the primary motivations for development of instrumented indentation was to measure the mechanical properties of thin films. Characterization of thin film mechanical properties as a function of temperature is of immense industrial and scientific interest. The major bottlenecks in variable temperature measurements have been thermal drift, signal stability (noise) and oxidation of/condensation on the surface. Thermal drift is a measurement artifact that arises due to thermal expansion/contraction of indenter tip and loading column. This gets superimposed on the mechanical behavior data precluding accurate extraction of mechanical properties of the sample at elevated/cryogenic temperatures [1]. Reliable load-displacement measurements up …

Revealing Dislocation Structure Around And Underneath Indentations In (001) Strontium Titanate Single Crystals At Room Temperature And 350o C, Farhan Javaid, Kurl Johanns, Karen Durst

Nanomechanical Testing in Materials Research and Development V

Many crystalline materials exhibit an indentation size effect, i.e., an intrinsic change in hardness with changes in sampled material volume. During indentation testing, the material underneath the indenter is heavily deformed, introducing high local dislocation densities and density gradients. In the present work, dislocation structures around and underneath the Vickers and Berkovich indentations performed at room temperature and 350^oC have been resolved in (001) oriented strontium titanate (STO) single crystal via a sequential polishing, etching, and imaging technique. Laser and atomic force microscopy were used to image dislocation etch-pit patterns which were then digitized for calculating dislocation densities, …

About The Plastic Response Of Silicate Glasses At The Micronscale, Guillaume Kermouche, D. Tumbajoy, P. Gangster, B. Mantisi, G. Molnar, A. Tanguy, R. Lacroix, V. Pukhkava, J. Teisseire, G. Guillonneau, J. Michler, E. Barthel

Nanomechanical Testing in Materials Research and Development V

Despite their brittleness, silicate glasses undergo plastic deformation at the micron scale. Mechanical contact and indentation are the most common situations of interest. The plasticity of glasses is characterized not only by shear flow but also by a permanent densification process.

We present novel observations of the deformation and fracture of amorphous silica micropillars of various sizes using In Situ SEM Micro-Compression (Fig 1), that can help better understand the mechanisms occurring prior to its fracture [1]. Exhibiting one of the highest ratios of shear stress on shear modulus, fused silica thus further distinguishes itself from other amorphous materials. Moreover, …

An Improved Micromechanical Method For Investigating The Mechanical Properties Of Poly-Silicon Membranes, Holger Pfaff, John Brickner, Ellen Auerswald, Dietmar Vogel, Sven Rzepka, Alfons Dehe

Nanomechanical Testing in Materials Research and Development V

Freestanding poly-silicon membranes are of increasing importance for designing MEMS devices such as pressure sensors, microphones and gyroscopes. It is crucial to accurately determine the mechanical properties of such membranes not only to access parameters for designing new devices but also for assuring proper performance and quality in service. Classically, microscopic tensile tests [1-3] or bulge tests [4] were conducted to obtain Young’s modulus and strength of the membrane material. These methods however are prone to artifacts due to crack initiation at edge defects (e.g. predefined notches in tensile specimens [3] or slits in bulge test samples [4]). In search …

Multiscale Characterization Of The Micromechanics Of Pure Mg, Jon Molina-Aldareguia, Raul Sanchez-Martin, Carmen Cepeda-Jimenez, Teresa Perez-Prado

Nanomechanical Testing in Materials Research and Development V

An important limitation of wrought (rolled and extruded) Mg alloys is their inherent strong mechanical anisotropy, a consequence of their hexagonal closed- packed (hcp) lattice. Several reasons contribute to this effect. First, at room temperature, the critical resolved shear stresses (CRSSs) of basal and non-basal slip systems have very different values, spanning several orders of magnitude; second, twinning, a very common deformation mechanism in these materials, exhibits a pronounced polarity, i.e. its activation is dependent on the relative orientation between the c-axis and the applied stress; finally, both hot and cold deformation processing textures are often quite sharp and the …

Size Effects And Deformation Mechanisms In Diamond And Silicon, Jeffrey Wheeler, R. Raghavan, J. Rabier, J. Wehrs, J. Michler

Nanomechanical Testing in Materials Research and Development V

At ambient temperature and pressure, most of the semiconductor materials are brittle. Traditionally, use of confining pressure via indentation or a hydrostatic confining medium [1, 2] has been required to study the plasticity of such brittle materials. In the case of group IV semiconductors (Diamond, Silicon, and Germanium) the situation is further complicated by pressure-induced phase transformations occurring underneath the indentations. However, previous work has demonstrated that sample miniaturization can also prevent the onset of cracking and allow plastic deformation [3]. Recent advances in in situ instrumentation have enabled micro-compression techniques to extract temperature- and …

Toward The Understanding Of The Brittle To Ductile Transition At Low Size In Silicon: Experiments And Simulations, Firas El Nabi, Laurent Pizzagalli, Sandrine Brochard, Cristophe Tromas, Ludovic Thilly, Julien Godet, Michael Texier, Olivier Thomas

Nanomechanical Testing in Materials Research and Development V

While bulk silicon is brittle at temperatures below 600-700K, the compression of nanopillars has shown that a decrease of the diameter below few hundreds of nanometers could change the silicon behavior from brittle to ductile [1,2]. This size effect cannot be explained by the initial defect density like in metals, because pristine silicon nano-objects do not contain residual defects. In these conditions the cracks and/or the dislocations nucleation should take origin at the surface. The identification of the parameters governing the brittle to ductile transition in size and the understanding of the mechanisms are the key points to further develop …

Thermally Activated Processes In Materials Probed By Nanoindentation - Challenges, Solutions, And Insights, Verena Maier, Alexander Leitner, Sandra Korte-Kerzel, Karsten Durst, Reinhard Pippan, Daniel Kiener

Nanomechanical Testing in Materials Research and Development V

Nanoindentation experiments are widely used for assessing the local mechanical properties of materials. In recent years some new exciting developments were established for also analyzing thermally activated processes during deformation using indentation based techniques, namely nanoindentation strain rate jump and nanoindentation long term creep tests. For these different methods, control of the indenter tip movement as well as determination of the correct contact conditions are hugely important to assure reliable data. In fact, long term nanoindentation tests are prone to be strongly influenced by thermal drift, starting at room temperature but even more intensified for elevated temperatures.

This talk will …

Boundary Motion Coupled With Tensile And Compressive Deformation: Tem Observation Of Twinning-Like Lattice Reorientation In Mg Micropillars, Evan Ma, Bo-Yu Liu, Zhi Shan

Nanomechanical Testing in Materials Research and Development V

For magnesium and some other hexagonal-close-packed metals, twinning on the plane is a common mode of plastic deformation. Recently, we have used in situ transmission electron microscopy (TEM) to monitor the deformation of submicron-sized single-crystal magnesium, in quantitative compression and tension tests (B-Y. Liu et al., Nature Commun. 2014). We have observed the reorientation of the parent lattice to a “twin” lattice, producing an orientational relationship akin to that of the conventional twinning. However, aberration-corrected TEM observations reveal that the boundary between the parent lattice and the “twin” lattice is composed of many segments of semi-coherent basal-prismatic (B-P) interfaces, …

High Temperature Indentation Creep And Nanoindentation Testing Of Superalloys And Tial Alloys, Mathias Goken, Markus Kolb, Doris Amberger, Steffen Neumeier, Jeff Wheeler, Johann Michler

Nanomechanical Testing in Materials Research and Development V

Measuring of the high temperature mechanical behaviour of materials by local testing has become a key task in the field of nanomechanics. However, gaining access to the application temperature of many metallic high temperature materials, which is in the range of 600°C - 1100°C, is quite difficult. In addition, creep parameters can only be determined by long time measurements, where drift influences become a severe challenge. Here we present a new approach of indentation creep testing with a flat punch indenter. For this, a thermo mechanical analyzer with very precise temperature control is used, which allows testing at temperatures up …

From Micro-Cantilever Testing To Deformation Patterning In Hcp Polycrystals, Angus Wilkinson, Jicheng Gong, T Ben Britton, Ed Tarleton, Daniel Balint, Micth Cudihy, Fionn Dunne

Nanomechanical Testing in Materials Research and Development V

For several years now we have been using micro-scale cantilever bend tests to probe the considerable anisotropy of elastic and plastic deformation behaviour in the hexagonal packed metals Ti and Zr [1-3]. The wider aim of the work has been understanding and modeling the heterogeneous patterns of stress, strain and dislocation density that develop during deformation of HCP polycrystals. Crystal plasticity finite element analysis (CP-FEA) of representative volumes are used to simulate these deformation fields and enable modelling of representative volume elements to aid understanding of in-service component performance. Critical resolved shear stress (CRSS) values for the important slip systems …

Understanding Rate Sensitivity In Dual Phase Titanium Alloys – A Combined Experimental And Computational Micro-Pillar Study, Tea Sung Jun, Zhen Zhang, Fion Dunne, Ben Britton

Nanomechanical Testing in Materials Research and Development V

Titanium alloys are used as structural load bearing components in aeroengines. In service, these alloys are subjected to significant cyclic loading, with high thrust (i.e. stress) excursions during take-off, a load-hold during flight and unloading on landing. The load-hold has been shown to have a significant effect on the fatigue life performance of many dual phase titanium alloys, where a significant hold at maximum load can reduce the number of cycles to failure by an order of magnitude or more when compared with simple ‘saw-tooth’ load-unload fatigue cycle. This is known as the dwell debit.

Recently, it has been demonstrated …

Nanoindentation Cartography In Al/Al-Cu-Fe Composites: Correlation Between Chemical Heterogeneities And Mechanical Properties, Christophe Tromas, Aurelie Joseph, Veronique Gauthier, Anne Joulain, Sylvain Dubois, Joel Bonneville, Dominique Evidi, Jean-Phillippe Monchoux

Nanomechanical Testing in Materials Research and Development V

During the last two decades, nanoindentation testing has become a commonly used technique for measuring surface mechanical properties such as hardness or elastic modulus. With devices equipped with a motorized X-Y table, it is now possible to perform large regular nanoindentation arrays in order to make an accurate statistics of the mechanical properties. This method is particularly interesting to study heterogeneous materials. The statistical analysis, associated to mathematical deconvolution methods allows identifying the properties of each individual phase. Furthermore, hardness or elastic modulus maps can be then established and compared to other local properties such as microstructure, crystallographic orientation or …

Mechanisms Of Plastic Deformation Of Magnesium Matrix Nanocomposites Elaborated By Friction Stir Processing, Camilla Mallman, Aude Simar, Emilie Derrie, Marc Fivel, Erica Lilleodden

Nanomechanical Testing in Materials Research and Development V

Magnesium based composites have attracted much attention over the past few years as a promising solution to lightweighting, energy saving and emission reduction, especially for automotive and aerospace applications. With a specific weight as low as 1.74 g.cm-3, magnesium is the lightest of all structural metals. However, the strength of Mg needs to be improved in order to compete with other light metals such as Al or Ti. The present study focuses on Mg reinforced by Y₂O₃ nanoparticles. The aim of the work is to investigate the single crystalline plastic behavior of Mg strengthened by oxide dispersed …

High-Temperature Small-Scale Fracture Mechanics And Plasticity Of A Hardcoating System, James Best, Johannes Zechner, Juri Wehrs, Johann Michler, Jeffrey Wheeler, Marcus Morstein

Nanomechanical Testing in Materials Research and Development V

Forging and cutting tools for high-temperature applications are often protected using hard nanostructured ceramic coatings. While a moderate amount of knowledge exists for material properties at room temperatures, significantly less is known about the system constituents at the elevated temperatures generated during service. For rational engineering design of such systems, it is therefore important to have methodologies for testing these materials to understand their properties under such conditions. Additionally, small-scale mechanical testing is of inherent importance for thin-films systems and materials subject to surface modification or treatment as for plasma nitrided steels.

In this work, we present results on both …

Probing Grain Boundary Mechanisms By In-Situ Tem, Frederic Mompiou

Nanomechanical Testing in Materials Research and Development V

In small grained metals, specific elementary deformation mechanisms such as GB sliding, dislocation emission from GB, shear coupled GB migration, grain rotation are expected to be active. However, their relative preponderance and activation during the overall plastic deformation is still difficult to assess, mainly because identifying these mechanisms in small crystallite at the appropriate time scale is a challenge.

To that respect, in-situ TEM experiments have proven to be an adequate tool to probe the dynamics of these mechanisms.

In this talk, I would like to report observations obtained during several in-situ straining TEM experiments in small grained Al (grain …

Can It Be Measured - Fracture Toughness From Repetitive Nano-Impacts Test?, Emilio Frutos, J.L Gonzalez Carrasco, T Polcar

Nanomechanical Testing in Materials Research and Development V

The design of coatings in the field of engineering applications aims at a progressive shift to the development of “hard but tough” coatings. The difficulty in assessing their mechanical behaviour by conventional methods is behind the growing relevance of “in situ” experiments using instrumented microindentation technique. This technique is one of the few able to investigate the mechanical properties along of whatever length range, i.e. from small volume to bulk material. Information from the load-depth curve of indentation has proven to be abundant and varied and it can be used to determine several mechanical properties such as: hardness, Young’s modulus, …

Size Effect On Fracture Toughness Of Gold Thin Films Studied By Bulge Testing, Eva Preisb, Benoit Merle, Mathias Goken

Nanomechanical Testing in Materials Research and Development V

A versatile bulge test setup was used to perform mechanical tests on rectangular gold membranes with thicknesses ranging from 100 nm to 350nm. It can be used in a conventional way to calculate stress-strain curves and determine parameters such as residual stress and plane-strain modulus. Alternatively, the setup in Erlangen can be inserted into an atomic force microscope (AFM) which allows in-situ imaging of the topography of the deforming membrane.

In order to determine the fracture toughness K_IC of thin films, narrow crack-like slits of 10 µm length were milled into the center of the membranes by focused ion …

Mechanical And Optical Properties Of Silicon Nitride Thin Films On Glass, Lukas Simurka, Selen Erkam, Tuncay Turutoglu

Nanomechanical Testing in Materials Research and Development V

Optical thin films have been widely used in glass coating industry for various energy saving applications such as solar control and low emissivity glasses. However, handling and processing of these systems can lead into various mechanical defects decreasing its lifetime and optical performance. Therefore, understanding and control of the mechanical properties plays an important role in thin films production. Silicon nitride is one of the most commonly used materials in the optical systems. Its high refractive index and good mechanical properties provide different functionalities. It can be used as a buffer layer for tuning of the optical performance or as …

In Situ High Temperature Tem Tensile Testing Of Pseudo Single Crystalline Si For Photovoltaic Applications, Arthur Lantreibecq, Etienne Pihan, Jean Francois Monchoux, Marc Legros

Nanomechanical Testing in Materials Research and Development V

Single crystalline Silicon has the highest efficiency to convert sunlight into electricity. Its production is however costly. On the other hand, cheap polycrystalline Si cells can be produced, with a 10% lower PV conversion efficiency. A promising technique, dubbed "mono-like" Si consists in growing pseudo-single crystalline Si ingots from a tile of single crystalline seeds aligned at the bottom of the crucible. At the present time, this technique is confronted to the high density of defects that multiply during solidification, fueled by the thermal gradients generated in the furnace. Some of these defects have small impact on the electrical properties …