Symposium CC
Modelling, Simulation and Testing of Mechanical and Thermomechanical Properties of Bulk Ceramics, Coatings and Composites
ABSTRACTS
CC-1:IL01 High Entropy Transition Metal Carbides – Compositional Space and Mechanical Properties
Y. Wang1, R. Zhang1, T. Casandi2, J. Dusza2, M.J. Reece1, 1Queen Mary University of London, London, UK; 2Institute of Materials Research, Slovak Academy of Sciences, Košice, Slovak Republic
The composition, structures and properties of transition metal mono carbides, binary carbides and multi-component carbides will be reviewed and compared in order to critically assess the compositional space and properties of high entropy carbides (>4 elements, with the metal elements in equiatomic proportions). The different methods in the literature to determine the synthesisability of high entropy carbides will be investigated; this will include ab-initio calculations and simple correlations. Some new and surprising stable multi-component compounds will be synthesised to validate the methods. The temperature phase stability and oxidation resistance of the materials will be investigated. It has already been shown that high entropy carbides can have significantly higher hardness and yield stress compared to mono carbides and binary carbides. In this work we present a systematic study of the mechanical properties of multi-component compounds in order to determine the effect of multi-components on mechanical properties: nanoindentation hardness and elastic properties; cantilever strength and fracture behaviour.
CC-1:IL02 Deformation and Fracture of Advanced Ceramics at Small-Scale during Micro/Nano Mechanical Testing
J. DUSZA, Institute of Materials Research, Slovak Academy of Sciences, Košice, Slovak Republic
The deformation and damage characteristics of differently oriented WC grains/crystals in WC – Co, Si3N4 grains/crystals in reaction bonded Si3N4 system and ZrB2 grains/crystals in ZrB2 polycrystal were investigated. Depth-sensing nano-indentation and scratch tests of grains and micro-compression tests of micropillars prepared by focused ion beam from oriented facets of grains were studied. During micro-cantilever tests in bending deformation and fracture characteristics of these grains and grain boundaries have been investigated, too. The hardness and scratch resistance of the differently orientated grains showed significant angle dependence from the basal towards the prismatic directions. A strong influence of the grains orientation on compressive yield stress and rupture stress values was found during the micropillar test, too. The active slip systems for individual ceramics have been recognized. The different properties of the basal and prismatic planes was found to be connected with the different deformation mechanisms – slip and dislocation activities. The bending strength of micro-cantilevers was strongly dependent on the character of the cantilevers with highest bending strength for the cantilevers fabricated from one grain without a fracture origin.
CC-1:IL03 Meso-scale Mechanical Properties of Si3N4 Ceramics Measured using Microcantilever Beam Specimens
JUNICHI TATAMI, M. Uda, M. Iijima, Yokohama National University, Yokohama, Japan; T. Takahashi, T. Yahagi, Kanagawa Institute of Industrial Science and Technology, Japan
Since wear of ceramic materials is the fracture of a small area of the surface, it is important to obtain knowledge about the mechanical properties near the surface of the material. In particular, it is useful to know the strength and fracture toughness at mesoscale, which is the same size as the crystal grains and grain boundaries of ceramics. In this study, the mechanical properties of Si3N4 ceramic surfaces were measured by bending test using microcantilever beam specimens fabricated by focused ion beam technique. As a result, it was found that the intergranular fracture toughness of Si3N4 ceramics depended on the added rare earths. The strength at mesoscale was extremely high compared to that of the bulk Si3N4 ceramics. The strength was found to be decrease significantly when the surface was in contact with acid for several hours. These findings are useful to understand the wear of ceramics and to develop superior wear resistant materials.
CC-1:IL05 Influence of Structure and Design on Ballistic Performance of Ceramic Armor
E. MEDVEDOVSKI, Endurance Technologies Inc., Calgary, Canada
Advanced ceramics in armor systems allow defeating the projectile and ballistic impact energy dissipation providing adequate ballistic protection. The development of lightweight and inexpensive ceramics and armor designs is under ongoing attention by both ceramic armor manufacturers and users. This presentation summarizes the results of extensive studies of structure, properties and ballistic performance of different armor ceramics, mostly obtained at the development, and the designed ceramic-based armor systems. These materials include homogeneous oxide (e.g., alumina, alumina-mullite and alumina-zirconia) and carbide ceramics and heterogeneous SiC-based ceramics. Ballistic performance of the studied ceramics as a function of their structure and properties, armor system design and type of projectile will be discussed. Depending on the requirements for ballistic protection, armor systems may be designed and manufactured to various configurations and weights combining the most suitable ceramic and backing materials. The examples of successful lightweight armor systems’ designs with adequate ballistic performance, including satisfactory multi-hit performance, for body armor, armor vehicles and structural application, will be demonstrated.
CC-1:IL08 Hot-pressed Ultra-high Creep Resistant Silicon Carbide Ceramics
P. SAJGALIK, Slovak Academy of Sciences, Bratislava, Slovakia
Freeze-granulated and afterwards under infrared lamp annealed silicon carbide powder was densified to the full density without any sintering aids by hot-pressing/ultra-rapid hot-pressing at 1850 °C. This densification temperature is at least 150-200 °C lower compared to the up to now known solid state sintered silicon carbide powders. Presented silicon carbide hot-pressed ceramics have excellent mechanical properties. Samples densified by ultra-rapid hot-pressing have also full density and hardness of 27.4 GPa. Partial phase transformation beta/alpha - SiC was observed in the granulated and hot-pressed/rapid hot-pressed samples. Creep rate of rapid hot-pressed samples at 1450 °C and 100 MPa load in 4-point bending test is 3.8 x 10-9 s-1 and at 1400 °C and the same load conditions is 9.9 x 10-10 s-1. Creep rate of the same at load of 400 MPa and temperature of 1750 °C at a comprersion mode was only 10-7 s-1. This is the lowest creep rate of SiC at such conditions found in the literature. Enhanced beta/alpha SiC phase transformation was observed after the creep test. The oxidation behaviour of this way prepared SiC ceramics at 1350-1450°C/0-204h was investigated. This way prepared SiC ceramics is characterised by an high oxidation resistance (4.91x10-5 mg2/cm4h at 1450°C).
CC-1:L10 Simulation of Densification Behavior of Nano-powder in Final Sintering Stage
BYUNG-NAM KIM, K. Morita, T.S. Suzuki, J.-G. Li, National Institute for Materials Science, Tsukuba, Ibaraki, Japan; H. Matsubara, Tohoku University, Japan
Densification behavior of porous body is modelled and simulated in the final sintering stage. The porous body is represented as an aggregate of the sintering units of different pore sizes. Regardless of the pore size, all the sintering units have an identical porosity. The macroscopic porous body has the size (u) distribution of pores, which is represented as a function of (umax-u)1/mexp(-um), and the effect of the size distribution is examined on the densification behavior. The mechanical interaction between pores is analyzed to simulate the evolution of porosity characteristics as well as the densification kinetics. The mechanical response of densification is discussed with the microstructural changes, and the simulated results are compared with experimental ones. The simulation shows that the densification kinetics severely deviates from the conventional prediction for single-sized pores, and that the size distribution varies gradually to approach the function of m=3.5. The porosity decreases monotonically with time, and the rate is lower for smaller m-values. The densification rate for the size-distributed pores is lower than that for single-sized ones. The experimental relationship between the densification rate and the porosity could well be reproduced by choosing appropriate pore-size distributions. The simulation also shows that the sintering stress with densification amy increase or decrease depending on the size distribution.
CC-1:IL11 Atomic-scale Investigations of Deformation Behavior of Ceramic Materials
EITA TOCHIGI, Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
Deformation of crystalline materials is attributed to atomic displacements induced by mechanical stress. To understand the deformation behavior in detail, atomic scale analysis is essential. In this study, we investigate the mechanical responses of oxide crystals from nano to atomic scale. Firstly, the behavior of rhombohedral twinning in sapphire (α-Al2O3) is discussed. By in situ transmission electron microscopy (TEM) nanoindentation, we show that twinning/detwinning phenomena occurred by the glide motion of twinning dislocations on the matrix/twin interfaces. Furthermore, the atomic motions associated with the twinning dislocation glide is demonstrated by atomic-resolution scanning TEM and first-principles molecular dynamics simulation. It is revealed that the elementary process of the twinning corresponds to cooperative motions of a grope of five atoms. Secondly, we introduce a custom-made loading device for in situ TEM mechanical experiment. The loading device was fabricated by micro electro mechanical system (MEMS) technique, and it has a good load resolution of sub-μN. We show some results of local strain changes in SrTiO3 upon loading measured based on atomic-resolution scanning TEM images.
CC-1:L12 Gas Pressure Sintered Si3N4: Extraction of the Sintering Parameters by In-situ Conventional Dilatometry
T. GRIPPI1, 2, 3, S. Behar-Lafenetre2, H. Friedrich3, D. Haas4, U. Schenderlein4, C. Manière1, S. Marinel1, 1Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, Caen, France; 2Thales Alenia Space, Cannes, France; 3Fraunhofer HTL, Bayreuth, Germany; 4FCTI, Rauenstein, Germany
In a view of modeling the sintering of Si3N4 by Finite Element Model, it is necessary to get sintering parameters (activation energy, moduli, etc.). In this work, we have used a dilatometric system adapted to the Gas Pressure sintering process. This instrumented sintering process has been used to sinter Si3N4 and the collected shrinkage data have been exploited through the constant heating rate methods (Master Sintering Curve (MSC) or Wang and Raj’s regression (WR)). In a first part, the furnace-dilatometric measurement system will be shortly detailed: - FPW 125/180-2200-100-D at FCTI based in Rauenstein, Germany equipped with a conventional dilatometer 1000/2200-100 (KCE System) In a second part, the extraction of the sintering parameters will be depicted. The activation energy, the viscosity, moduli and sintering force/swelling competitions will be studied by using MSC and WR methods from three different cycles with different constant heating rates. Key words: Silicon Nitride, Sintering behavior, gas pressure sintering, conventional dilatometry.
CC-1:IL15 Control of Dislocation Behavior to Improve Low Temperature Plasticity of Ceramic Materials
A. NAKAMURA, Osaka University, Toyonaka, Osaka, Japan
The plasticity of a crystal is determined by the internal dislocation behavior. Therefore, the plasticity of ceramic materials can be altered by controlling the dislocation behavior. In alumina, a typical ceramic material, slip deformation via dislocation glide in a crystal can be realized at lower temperatures by pre-multiplying dislocations at higher temperatures (Acta Mater., 2005). The behavior of dislocations can also be controlled by external fields other than the force field. As an example, the dislocation behavior can be changed by controlling the light condition (Science, 2018, Acta Mater 2020). Here, such a method to control the dislocation behavior and improve the plasticity of ceramics at low temperatures will be discussed, including the latest research results.
CC-1:IL16 Unexpected Law for Grain Growth in Twinned Boron Carbide Ceramics Fabricated under Electric Field
D. Gómez García, Department of Condense Matter Physics, CSIC, University of Seville, Seville, Spain; B.M. Moshtaghioun, Department of Condense Matter Physics, CSIC, University of Seville, Seville, Spain
This study reports the first experimental evidence of the violation of the classical law for grain growth in twinned boron carbide ceramics. Grain-growth kinetics is drastically dependent on the presence of twin steps at the grain boundaries in B4C ceramics sintered by spark plasma sintering. The conjunction of high temperature gradients with large compressive stress when a pulse electric current passes through the ceramic powders gives rise to an intense twinning–detwinning formation. These forming steps at the grain boundaries change the grain mobility drastically. Therefore, a new ‘exotic’ law for grain-growth kinetics is found and validated at different temperatures and dwell times. The time dependence of the grain size is proved to follow one law which has the same functional form as the Bose-Einstein distribution law.
CC-2:IL02 CMAS Induced Microstructure Degradation of Thermal Barrier Coatings for Application in Gas Turbine Environments
D.E. MACK1, G. Bruno2, 3, O. Helle1, O. Jarligo1, J. Malzbender4, B.R. Müller2, R. Vaßen1, 1IEK-1, Forschungszentrum Jülich GmbH, Jülich, Germany; 2BAM, Bundesanstalt für Materialforschung und -Prüfung, Berlin, German; 3University of Potsdam, Institute of Physics and Astronomy, Potsdam, Germany; 4IEK-2, Forschungszentrum Jülich GmbH, Jülich, Germany
The degradation of ceramic thermal barrier coatings (TBCs) due to calcium-magnesium-aluminosilicate (CMAS) glassy deposits from various sources has become a persistent challenge. The corrosive attack induced by these molten deposits imposes major changes on microstructure and chemistry of the outer coating layers, which also affects their thermo-mechanical properties. State of the art electron microscopy was correlated with X‐ray refraction techniques to elucidate the intrusion behavior of CMAS into the porous structure of atmospheric plasma sprayed (APS) yttria-stabilized zirconia (YSZ) TBCs as well as the formation and propagation of cracks under cyclic loads in a burner rig. The resulting mechanical degradation of the coatings was studied by means of instrumented micro indentation. The results indicate that the sparse nature of the infiltration as well as kinetics of degradation in the burner rig are mainly influenced by the wetting behavior of molten CMAS compounds. While the Young’s modulus of the TBC shows close correlations to the level of CMAS intrusion, chemical interaction of YSZwith CMAS appears to have no immediate impact on structure and density of internal surfaces. At later stages, the formation of delamination cracks is observed in a wider zone of the TBC layer.
CC-3:IL01 Interfacial Fracture Toughness on SiC/SiC CMCs
O. GAVALDA-DIAZ, L. Vandeperre, E. Saiz, F. Giuliani, Centre of Advanced Structural Ceramics, Department of Materials, Imperial College London, London, UK
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 propagation and measuring interfacial properties such as the fracture toughness, friction or residual stresses is crucial to understand, predict and model the failure of these materials and their degradation in different environments. In SiC/SiC materials the fibres are normally coated with graphite-like C or hexagonal BN interphases to achieve the desired interfacial properties. In this presentation we show different micromechanical tests that can be used to propagate a stable crack at the interfacial region and measure the interfacial fracture toughness. This includes micro Double Cantilever Beam (DCB) and push out tests using an SEM in-situ setup. With these tests we measure the Mode I and Mode II interfacial fracture toughness and we can distinguish the different debonding and fracture events as they occur. With this work we highlight possible routes for material optimisation.
CC-3:IL04 Residual Stresses and Texture Characteristics in Si3N4 Ceramic Composites
C.C. Ye, School of Mechanical-Electronic and Vehicle Engineering, Weifang University, Weifang, Shandong, China; H.Q. Ru, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Institute of Ceramics and Powder Metallurgy, School of Materials Science and Engineering, Northeastern University, Shenyang, Liaoning, China; DAOLUN Chen, Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario, Canada
Silicon nitride (Si3N4) is one of the most promising structural ceramics due to its excellent strength, chemical stability, low coefficient of thermal expansion, high toughness and good thermal shock resistance. The introduction of sintering additives (metal oxides and rare-earth oxides) into the Si3N4 can significantly influence fracture toughness. The thermal mismatch between the silicon oxynitride-based glasses and β-Si3N4 grains can generate a certain extent of residual stresses. In the present study X-ray diffraction was used to determine crystallographic textures and residual stresses in Y2O3-Al2O3-Si3N4 and Y2O3-MgO-Si3N4 ceramic composites. The obtained results revealed that the glass phase in the Si3N4 matrix played an important role in affecting crack deflection and rod-like grain pull-out mechanisms. Meanwhile, the controlled development of textured microstructure also affected fracture toughness, where the {0001} planes of most rod-shaped β-Si3N4 grains were oriented in the hot-pressing direction of the sintered cylinder-shaped samples. The obtained indentation fracture toughness varied when the indentation angles deviated from the plane parallel to the hot-pressed direction. Details of the study will be presented at the conference.
CC-3:IL05 Damage and Stress Evolution in Multi-phase Metal Matrix Composites
G. BRUNO, S. Evsevleev, T. Mishurova, S. Cabeza, BAM, Berlin, Germany; G. Garces, CENIM, CSIC, Madrid, Spain; G.Requena, DLR, Cologne, Germany; I. Sevostianov, NMSU, Las Cruces, NM, USA
While there is an extensive literature on the micro-mechanical behavior of metal matrix composites (MMCs) under uniaxial applied stress, very little is available on multi-phase MMCs. In order to cast light on the reinforcement and damage processes in such multi-phase composites, an Al alloy with one and two ceramic reinforcements (planar-random oriented alumina fibers and SiC particles) were studied. In-situ compression tests during neutron diffraction experiments were used to track the load transfer among phases, while X-ray computed tomography was used to investigate pre-strained samples, in order to monitor and quantify damage. We found that damage progresses differently in composites with different orientations of the fiber mat. Because of the presence of the intermetallic network, it was observed that the second ceramic reinforcement changes the load transfer scenario only at very high applied load, when also intermetallic particles break. We rationalized the experimental results by means of a micromechanical model based on Maxwell’s homogenization scheme, and we could explain why no damage is observed in the ductile matrix under compression: the matrix finds itself in hydrostatic compression, and the Poisson’s tensile strain is totally carried by the reinforcement phases.
CC-3:IL06 Microstructure Design and Mechanical Properties of Ceramic/Graphene Thick Coatings for New Emerging Applications
C. BALAZSI, Centre for Energy Research, Budapest, Hungary
The influence of the various content of the multilayered graphene (MLG) on the structural and mechanical properties of the final bulk porous silicon nitride-zirconia (Si3N4-ZrO2) based ceramics was investigated. The ceramic composites were prepared in the form of the laminated structure with different (5-30-5 wt% and 30-5-30 wt%) MLG content by hot isostatic pressing. ZrO2 particles were incorporated into the Si3N4 matrix by attrition milling to improve the mechanical properties of the final composite. Homogeneous distribution of the MLGs, a completed phase transition from α to β-Si3N4 in case of 5 wt% MLG have been observed. The structural examinations revealed that the multilayered graphene and zirconia particles owing to their different sizes and shapes influenced the porous microstructure evolution and the related mechanical properties of the composites. The sandwich structures enhanced the mechanical properties compared to reference ceramic with 30 wt% MLG. The position of the layer with higher graphene content, high ratio of alfa / beta phase of Si3N4 and higher porosity had crucial effect on the final mechanical properties.