EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Mg-Al-Ca alloys are well-known for their excellent creep resistance at elevated temperatures. This is due to the intermetallic network of Mg-Al-Ca Laves phases that strengthens the alloy. In this work, we have looked at deformation of the individual phases (intermetallics and α-Mg), their co-deformation at interfaces and the overall deformation of the composite using nano- and micromechanical...

Non-metallic inclusions such as oxides are commonly present in all steels as a result of steelmaking processes. These inclusions are important because they influence the mechanical properties of the material. Current knowledge concerning compositions, formation and growth mechanisms of inclusions in steel is rather well-established; however, their intrinsic mechanical properties are less well...

Barium Titanate (BTO) is a widely accepted lead-free piezoelectric ceramic used at micron length scales and in thin film forms in MEMS applications. Deviation in material properties from its bulk counterpart due to size effects makes it essential to estimate the properties in the real length scale of applications. Here we study the mechanical behaviour BTO single crystals and thin film systems...

Recent work using micropillar compression has shown that the stress for ideal dislocation slip transmission through a coherent twin boundary (CTB) in copper is similar to the stress required for dislocation cross-slip [1]. The difference in shear stress during deformation of single and bi-crystalline micropillars (Δ2%) can be as low as 7 MPa for 3 µm sized pillars. A double-hump dislocation...

The limited ductility of metallic thin films (< 1%) poses a challenge to flexible electronics applications. There are only few exceptions to this rule. For this study, we selected remarkable gold films with a ductility > 10% and engaged into advanced nanomechanical characterization to identify the underlying physical mechanisms. From in-situ microtensile tests in a transmission electron...

Nanocrystalline (nc) materials are used in a large variety of micro- and nanoscale devices. The reliability of these devices requires maintaining adequate mechanical integrity of structural elements over time. This represents a real challenge due to their far from equilibrium microstructure. The stability of nanocrystalline materials is most often addressed in the literature in terms of...

High performance applications require materials that combine damage and fracture tolerance with high strength. For such applications tungsten based alloys and composites are frequently considered as candidates. Alloying and composing are both concepts commonly used to improve the ductility of tungsten. However, to exclude brittle inter-metallic phase formation, the former requires use of...

Repeated heat pulses can cause metallizations on substrates to suffer from gradual microstructural degradation. In this work a study on the thermo-mechanical fatigue behavior of electrochemically deposited (ECD) copper line structures on actively heated microchips is presented. In particular, a comparison between two different types of copper, corresponding to different electrolytes used for...

Body-centered cubic metals like Molybdenum and Tungsten are interesting structural materials for high temperature applications. These metals, are however, brittle at low homologous temperature, caused by the limited mobility of screw dislocations. In this study, the thermally activated deformation mechanisms in bcc Mo have been investigated using strain rate jump nanoindentation and...

Microcomponents, such as microchips, actuators and sensors, are often based on metallic thin films that must endure cyclic thermomechanical loading during their lifetime. The mechanical properties of these thin films are usually different from bulk materials and their thermomechanical fatigue mechanisms are poorly unknown. For this reason, an advanced bulge test setup was developed to...

Metallic glasses (MGs) have been intensively studied since the 60’s, for their amorphous structure, their global chemical homogeneity and their lack of crystallographic defects, leading to unique characteristics. From a mechanical viewpoint, MGs are characterized by outstandingly high elastic domain and maximal strength, compared to their crystalline counterparts. Although they are...

Infrared detectors based on II-VI semiconductors are cooled from room temperature (RT) to cryogenic temperatures between 80 K and 150 K in order to operate with strong requirements regarding sensor performances for infrared detection. At these cryogenic temperatures, the mechanical properties of II-VI alloys have to be known in details to improve both handling, use and lifetime of infrared...

Although extensive experimental and simulation researches have been devoted in the past to study the mechanical behaviour of metallic glasses, the elementary deformation mechanisms in these complex systems are not well documented and still a subject of open debates. Recent studies have shown that the brittle-like behaviour of bulk metallic glasses (~ 2%) is mitigated when the sample size is...

Digital image correlation (DIC) is a powerful technique allowing detailed mapping of local strain distributions from the images of deformed surface. Spatial resolution of DIC is restricted only by the pixel size of the image and quality of random speckle pattern on the surface. Here we demonstrate the capabilities of DIC to capture propagation of shear bands in thin film metallic glasses with...

The improvement of the thermomechanical performances of coatings is more than ever a major challenge in, among others, energy production, transportation, environment and biomedical engineering fields which many components undergo severe tribological solicitations. The durability of coatings often controls the durability of the devices and structures, hence their safety, efficiency and...

Brittle layers are often dominating the fracture behavior of flexible thin film multilayer structures through stress concentration, whereby the modulation period (tbrittle + tductile, film thickness t) and the modulation ratio (tbrittle/tductile) influence the extent of embrittlement. A promising strategy to avoid brittle fracture in multilayers is the combination of atomic layer (ALD) and...

Introduction/ Purpose
In contrast to macroscopic fatigue testing, local fatigue experiments on microsamples offer an opportunity to study the crack growth behavior in-situ with correlative microscopy. The basis for this is the combination of microscale sample fabrication by Focused Ion Beam milling and nanoindentation cyclic actuation [1, 2]. The extension of this method by notched...

In the field of electronics, there is a strong push towards miniaturization of current devices. Modern electronics consist of various combinations of layered materials with different material properties, enabling the desired device properties. Their interfaces are assumed to be a weak-points and, therefore, must be investigated.
Measurements of the adhesion energy of the thin film on the...

SiC/SiC CMCs are currently under investigation for application in the aerospace and nuclear industries: for example, SiC/SiC started replacing some of the Nickel-based superalloy components used in the hot section of aeroengines. Internal interphases in SiC/SiC are designed to achieve the graceful failure required in structural applications. Consequently, understanding interfacial crack...

Modern technological devices rely on a multitude of constituents with local variations on the micrometre to nanometre scale. Specifically, in the microelectronics industry, where very confined regions are precisely processed for individual functionalities, e.g. semiconducting properties, diffusion barriers, heat sinks, etc., this is observed quite frequently. Therefore, a need for materials...

Indentation is a versatile method to assess the hardness of different materials along with their elastic properties. Recently, powerful approaches have been developed to determine further material properties, like yield-strength, ultimate tensile strength, work-hardening rate and even cyclic plastic properties by a combination of indentation testing and computer simulations. The basic idea of...

Machine learning algorithms have already been used to interpret indentation data. In this study, different machine learning models will be used on data with different fidelities, closing the gap from 2D and 3D simulations to actual experiments using Residual Multi Fidelity Neural Networks combined with transfer learning and other machine learning techniques. Finite element produced data will...

Large-scale atomistic simulations with pre-existing defects are rare, but have recently shown promising potential to study defect-defect interactions in a more realistic fashion. Hitertho, atomistic simulations of nanoindentation to determine the hardness of a material, were usually carried out on defect free crystals. While first investigations with a pre-existing dislocation density showed...

Nanoindentation is a commonly accepted technique that measures local mechanical properties. The timescale for a traditional nanoindentation test is on the order of minutes, allowing for spatially varied measurements on a material in the order of 100’s of indents. With the introduction of high throughput (XPM) indentation methods increases, datasets in the tens of thousands and, as recently...

The study of nano-particles (NPs) deformation has proved to be of high importance to understand elementary processes at small-scale, with several applications as in the fields of catalysis,nanomaterial engineering and medical imaging. Indeed, NPs are characterized by high yield strength and ductility, when compared to their bulk counterpart, that are mostly attributed to surface mechanisms....

Hertzian theory is a classical approach to analytically describe an elastic interaction between solids in contact assuming that their mechanical properties are homogenous, the evolved strains are small, and the surfaces in contact are frictionless, continuous and non-conforming. The theory is central to numerous scientific domains and engineering applications, and it is at the foundation of...

Mechanical failures in microelectronic devices, such as delamination and cracking, play a key role for reliability concerns in today’s Back-End-of-Line structures. During use temperature differences can cause high stresses because of the CTE mismatch of the contained mechanically highly diverse materials. These stresses can cause delamination of the interfaces, which then affects the lifetime...

It is well known that creep effects can be observed during nanoindentation experiments when the load is hold constant at maximum force. Many attempts have been made to correlate nanoindentation creep curves under constant load obtained with sharp or spherical indenters with the results of macroscopic creep tests. However, they failed because the depth change under load is accompanied by a...

We present recent experimental and numerical data on the compression behavior of single crystalline and core-shell metal nanoparticles. Single crystalline samples deform elastically up to very high level of stresses approaching the theoretical shear strength. The following catastrophic plastic collapse is characterized by multiple dislocation nucleation events in the pristine nanoparticles. In...

In order to comprehend the fracture resistance of nanocrystalline protective thin films, it is vital to elucidate the multiaxial stress fields throughout irreversible deformation. In this work, a notched double-clamped cantilever with dimensions of 200×23.7×40μm³ was cut by focused ion beam milling from a 21.7µm thick thin film composed of four alternating CrN and Cr layers on high-speed...

The correlation of digital images obtained during deformation allows quantifying the different components of the local displacement and thus, the 2D local strain tensor. Typically, conventional optic systems for image acquisition lead to maximum strain resolutions ranging few micrometers. During the last five years, the micromechanics research community has been performing huge efforts in...

In recent years, different techniques have been established for in situ testing of nanostructures, revealing a size-dependency of the properties commonly referred to as size effect. While for plastic deformation a general trend of “smaller is stronger” is well-established, such a general observation has not been made for elasticity. For metal nanowires different results regarding the Young’s...

Bridging the gap between fundamental nanomechanical research and device engineering requires the application of innovative testing techniques under realistic loading conditions. One of the most prominent examples for nanomaterials based devices are highly flexible transparent electrodes consisting of a percolated nanowire network on a polymer substrate. To optimize the overall performance and...

Shifts of the carrier mobility in strained transistor channels are reported due to changes of the silicon band structure [1]. This effect depends on the used technology and the applied stress-strain fields. The piezoresistive coefficients of the channel material describe the sensitivity of the transistors to stress. The mentioned strain effect can be used to enhance the performance of...

Cerium oxide is widely used in many applications, such as in solid oxide fuel cell electrodes, catalysis, or gas detection. There are, nevertheless, few experimental evidences to show the evolution of defects in this structure which may have a significant impact on many properties, especially on mechanical behavior.

In situ nanocompression experiment in a transmission electron microscope...

Mechanical properties of materials in small dimensions have become an important area of fundamental research, including the development and introduction of new techniques for micro- and nanomechanical testing. A miniaturised micro double-cantilever beam test (micro-DCB) setup was designed and integrated into a laboratory transmission X-ray microscopy (TXM) tool to study the fracture behaviour...

We present quantitative in-situ Transmission Electron Microscopy (TEM) fracture experiments on single crystal Silicon at room temperature. Findings consist of a brittle bulk fracture behavior of large samples at a stress intensity K_IC~1 MPa.m^(1/2). However, below characteristic dimensions of about 250 nm, the fracture toughness strikingly increases inversely with size to at least...

High angular resolution electron backscatter diffraction technique (HR-EBSD), coupled with a SEM in-situ nanoindenter, allows characterizing microstructural changes, strains, stresses and lattice defects evolution during deformation with a sub-100nm resolution, and while the mate-rial is under load, making it ideal to study small-scale mechanics. However, HR-EBSD is a near surface technique,...

Digital Image Correlation (DIC) performed on in-situ Scanning Electron Microscopy (SEM) data provides detailed identification and analysis of micromechanical deformation mechanisms, such as crystallographic slip, grain boundary sliding, etc. By analyzing full-field displacement and/or strain maps, quantitative data, on e.g. slip activity, can be obtained for polycrystalline materials, which...