ICMCTF 2026 Session CM2-1-ThM: Advanced Mechanical-Physical Testing of Surfaces, Thin Films, Coatings and Small Volumes I

In light of the increasing interest in dislocation-tuned physical properties and the technological potential that dislocations may hold in ceramics, research on dislocations in ceramics is drawing renewed attention. To facilitate the dislocation research in ceramics, the pressing challenge is to engineer dislocations into brittle ceramic materials without inducing cracks. To this end, we have separately examined the dislocation behavior, including dislocation nucleation, multiplication, and motion, enabling us to tailor dislocations into some ceramic materials at room temperature. We can now achieve a dislocation density ranging from ~10¹⁰/m² to ~10¹⁵/m² in the near-surface region, with a plastic zone size of up to millimeters, using the deformation toolbox developed in our group since 2019. This toolbox allows us to further build on dislocation engineering beyond the near-surface region, going into the thin films and studying the dislocation-tuned mechanical and physical properties. In this talk, I will first introduce the room-temperature dislocation engineering toolbox. Then I will focus on the mechanical and functional properties tuned by the near-surface dislocations as well as in the dislocation-engineered thin films. The proofs-of-concept on the model perovskite SrTiO₃ will be demonstrated to showcase the applicability.

Nitride ceramic coating materials exhibit several advantages over metals, including superior hardness, wear resistance, thermal stability, and oxidation resistance [1-3]. With the growing need for industrial applications and environmental considerations, developing new composite nitride coatings that are both economically and environmentally friendly has become a challenging task. Using the architectural structure design of the interface and planar defects could be one approach. Along this line, we made some progress.

The extensive high-resolution transmission electron microscopy (HRTEM) observations of the TaN/TiN multilayer reveal that dissociation of full dislocations results in a network of stacking faults (SFs) and the formation of Lomer-Cottrell lock arrays within the TaN layer. Consequently, the high density of stacking faults dramatically strengthens the TaN/TiN multilayer [1]. Using valence electrons and inner shell electron spectroscopy, a combined experimental analysis of a multilayered structure of CrN/AlN allowed for the mapping of the multilayer's mechanical properties (bulk modulus) at the nanometer scale [2].

We observed atomic-scale intermixing in the nanoscale TiN/AlN multilayer by combining cross-sectional FIB cutting with atomic-resolution electron microscopy. A new solid-solution phase formed, as evidenced by mapping electronic structure differences. Using atomic EDS, we further corroborated that a homogeneous solid-solution zone formed upon loading [3].

From atomic-resolution observations, we first revealed that deformation in vacancy–engineered WNx/TiN multilayers can also be achieved through unit-unit disturbance. Instead of dislocation motion, multiple local unit-cell-scale disturbances can dissipate local strains, thereby releasing stress concentrations and enabling large-scale deformation. This mechanism leads to a significant enhancement of mechanical properties [4]. Moreover, one remarkable advancement is the discovery of an approach that successfully introduces a large density of nanotwins into nitride ceramics [5]. The synergy between the strength and toughness of nitride ceramics is enhanced. [5]

[1] Yong Huang et al., Acta Materialia 255 (2023) 119027

[2] Zaoli Zhang et al., Acta Materialia, 194(2020) 343

[3] Zhuo Chen et al., Acta Materialia, 214(2021)117004.

[4] Zhuo Chen et al., Nature Communications, (2023)14:8387

[5] Yong Huang, et al., Acta Materialia 299 (2025) 121475

Acknowledgment: This work is financially supported by the Austrian Science Fund (FWF PAT1946623). The authors would like to thank Prof. Christian Mitterer and Paul Heinz Mayrhofer for delivering the samples, and David Holec for performing DFT calculations.

Understanding the deformation behavior of metallic thin films at small scales is essential for advancing nanoscale devices and coating performance. Mechanical properties are strongly governed by microstructural features such as grain size, defects, and interfaces, leading to pronounced spatial variations in elastic and plastic response and thus controlling failure. Conventional macroscopic testing is unable to resolve these local effects. In this talk, we present the recent progress in probing the nanoscale deformation mechanisms of metallic thin films at the nanoscale using four-dimensional scanning transmission electron microscopy (4D-STEM). This technique enables in-situ strain and crystal orientation mapping with nanometer spatial resolution during simultaneous mechanical loading inside the transmission electron microscope. Utilizing this advanced characterization technique, we aim to provide quantitative insight into the local strain evolution, stress redistribution, and defect activity that lead to material failure. The results demonstrate how 4D-STEM serves as a powerful tool for linking microstructure and mechanical performance. These insights provide a foundation for designing new material systems with tailored mechanical performance and improved reliability through nanoscale structural design.

Combinatorial thin-film libraries are rapidly transforming the exploration of complex metallic alloys, yet the ability to interpret their mechanical behavior across broad compositional gradients remains a significant challenge. High-speed nanoindentation mapping, combined with advanced data analytics, now provides the statistical depth and spatial resolution required to transform such coatings into quantitative mechanical datasets.

In this study, a compositionally graded Cr–Cu–Ti–W system was synthesized as a model platform to investigate how partial miscibility and non-equilibrium co-sputtering produce diverse architectures: from nanocrystalline solid solutions to amorphous metallic composites. More than 3,000 indents were acquired across 29 regions of interest, establishing position-resolved maps of hardness, modulus, and derived figures of merit (H/E, H³/E²). When correlated with local EDX composition and confirmed by STEM-EDS, the results reveal distinct mechanical regimes: Ti- and Cr-rich domains combine strength and compliance, whereas W-enriched regions exhibit high stiffness but limited deformability.

In this framework, unsupervised learning algorithms are applied to analyze the high-speed indentation dataset, identifying clusters of mechanical behavior. These mechanically defined clusters guide targeted investigations into microstructural and micromechanical properties. The analysis utilizes micropillar compression data from over 200 pillars across different regions of interest to directly assess yield strength and strain-hardening behavior.

Unsupervised learning and dimensionality-reduction algorithms classify the pillars based on their deformation responses and connect these classifications to local indentation signatures and transmission electron microscopy (TEM) resolved microstructures. This approach allows for the identification of recurring deformation patterns, such as shear localization, homogeneous flow, or cracking, that are associated with specific compositional and microstructural configurations.

This combined experimental–computational framework provides a pathway for the rational design of multicomponent coatings, in which mechanical functionality emerges from quantitative correlations across scales.

In the process of determining the elementary mechanisms of plastic deformation, micromechanical testing has opened up a new avenue. Nanoindentation testing induces plasticity into a micrometer size volume, providing a localized plastic deformation structure that is easy to observe and identify. A spherical tip, instead of a classical pyramidal tip, avoid stress concentrations and produces a long-range stress gradient, with regions in tension and others in compression or shear, providing a broad sample of the possible mechanism in a given area. Complementarily, compression tests performed using a nanoindenter, equipped with a flat punch, on micrometer-sized pillars prepared by focused ion beam (FIB), generate a uniaxial and uniform compressive stress, easier to analyze. Furthermore, thanks to in situ experiments, observation of the free surfaces of the pillars under compression provides dynamic information on the deformation process.

In this study, the plastic deformation mechanisms of the MAX phase Cr₂AlC (a nanolamellar material with a hexagonal crystallographic structure) is investigated using micropillars compressions experiments and spherical nanoindentation. In both cases, the deformation microstructure is analyzed by Transmission Electron Microscopy (TEM) on lamella extracted along different orientations, in combination with surface observation by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), and with local crystallographic misorientation maps (ACOM ASTAR). This approach allows us to study the role played by deformation twinning, kink bands and stacking faults in the plastic deformation processes in this material.

The present paper presents research conducted in the field of thermal spray coatings aimed at improving the properties of agricultural components. The studies focus on thermal plasma jet deposits using the APS (Atmospheric Plasma Spray) technique applied to agricultural plough components designed for soil processing. These components are subjected to extreme operating conditions during use, and their main required properties are wear and impact resistance - key performance factors that determine the plough's service life.

In the research, thermal coatings were produced using WC–12%Co–based metallic powders (commercial name WOKA 3101). On laboratory samples, mechanical properties were evaluated through tensile tests, micro-scratch testing, and determination of the coefficient of friction under both rotational and translational motion. Since these components experience significant operational stress, thermal spraying represents an effective method not only for improving the mechanical properties of newly manufactured parts but also for refurbishing worn elements to restore them to proper working condition.

Acknowledgment: This work was supported by a grant from the Ministry of Education and Research, CCCDI–UEFISCDI, project number PN-IV-PCB-RO-MD-2024-0336, within PNCDI IV