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

A detailed study is presented comparing the deformation mechanisms operating at service temperatures in the Ni-based disc alloy RR1000 during monotonic tensile, high stress creep and fatigue conditions. By using bright field conventional and scanning transmission electron microscopy to observe tests interrupted at low strain, it was possible to follow the sequence of events and highlight the...

High temperature and total strain controlled low cycle fatigue tests for smooth and notched specimen were carried out for the nickel base superalloy Rene80. Two different material batches were tested, where smooth specimen with a preferential grain orientation distribution showed distinct higher lifetimes compared to smooth specimen made of material with random grain orientation. However, for...

The main aim if this study is to investigate influence of coarse grained microstructure of a nickel-based superalloy on TMF crack growth behaviour. For this purpose, single-edge U-shaped notched (SEN) and corner crack (CC) specimens were machined and tested under out-of-phase (OP) and in-phase (IP) TMF crack growth test conditions between 400 and 750 oC in laboratory air. The loading waveform...

Aluminium castings often possess complex geometries with only selected surfaces machined. Thus, the overall fatigue assessment needs to cover the heterogeneously textured as-cast surfaces considering local casting process conditions as well.
Recent research activities of Pomberger and Oberreiter introduced an alternative sub-area based fatigue assessment methodology for as-cast and pore...

Low alloyed steel slabs produced by the continuous casting process can present transverse corner cracks, which cannot be repaired afterwards due to the formation of an oxide layer within the crack. Because of that, the understanding of the formation of these cracks, as well as the reproducibility of the phenomenon through laboratory tests is of great value. The present work analyzed samples...

Power electronic modules are integral for energy conversion in applications like renewable energy generation and transport. Sintered nanosilver die-attachments have been proposed as a more reliable and environmentally friendly alternative to solder alloy joints for emerging power electronics module designs. However, their degradation mechanisms are not as well understood. This talk is about...

Monitoring pressurized water reactors casted duplex stainless steel parts is of interest in long-term operation of nuclear power plants. It has been shown that these components are subjected to ageing when held at their operating temperature. In the long run, thermal ageing results in embrittlement due to a microstructural evolution of one of the two phases constituting duplex steels. Kinetics...

Titanium alloys oxidation leads to the simultaneous formation of an oxide layer and an oxygen-enriched layer below the oxide scale due to high solubility of oxygen in titanium. A few tenths of atomic percent of dissolved oxygen is sufficient to weaken the mechanical properties of titanium alloys. It is thus necessary to take into account the impact of this oxygen-enriched layer to predict...

Many applications of glass fibres reinforced laminates (GFRP) require stable properties along many years of use, thus studies on how they will behave under the influence of weather conditions are necessary. Satisfactory would be no changes or a slight decrease in the microstructure and mechanical properties that may indicate degradation resistance of the composite material.
The aim of the...

An integrated framework for deformation modeling has been developed, which combines a physical state parameter-based formulation for microstructure evolution during plastic deformation processes with constitutive creep models of polycrystalline materials. The implementations of power law, Coble, Nabarro–Herring and Harper–Dorn creep and grain boundary sliding are described and their...

The development of aeroengines with higher thermal efficiencies, has been facilitated by the advance in materials, notably the development of thermal barrier coatings and their testing techniques. The Small Punch Test (SPT) is a vastly used material test in industry, that is implemented to characterise mechanical behaviour of materials that are in a limited supply, such as thermal barrier...

This paper deals with ductile damage nonlocal modelling of semi-crystalline polyamides using state regularized formulation towards capturing ductile damage localization (softening) while overcoming spurious mesh sensitivity in the predictive numerical simulation. The mechanical behavior is simulated through a viscoelastic viscoplastic ductile damage model (VEVPD), from which the constitutive...

Accurate simulation of finite-temperature properties of metallic alloys is often a challenge for computer-aided materials design, mostly performed with density-functional theory (DFT) calculations.
Not only it requires time-consuming molecular dynamics (MD) simulations to capture finite-temperature effects, but also questions like phase stability at different temperatures arise and become...

Abradable coatings such as AlSi-PES and AlSi-hBN enable small tip clearances in aeroengine axial compressors by reducing the severity of blade-casing interactions. However, as these abradables are typically plasma sprayed onto the internal surfaces of the casing, the precise makeup and properties of every spray batch are not well defined. This poses significant challenges regarding the...

Tungsten and its alloys have emerged as the promising refractory materials to find applications in nuclear fusion reactors such as International Thermonuclear Experimental Reactor (ITER) and the Demonstration nuclear reactor (DEMO). Despite the attractive properties, limited ductility and high ductile to brittle transition temperature (DBTT) are observed in tungsten. Such behaviour is linked...

It is vitally important to consider time dependent (or “viscous”) deformation behaviors when formulating material models, particularly when elevated temperature conditions are present in the intended application. In many macroscopic modelling attempts, time dependencies are limited to “plastic” regions of deformation. Under such modelling paradigms stresses will, under periods of strain hold...

Aluminum is an excellent choice for structural applications in the aerospace industry due to its high strength-to-weight ratio. Aluminum alloys, especially high strength alloys, are however susceptible to corrosion and surface treatments are hence required to withstand the harsh environment of an aircraft.

Since 2017, the use of hexavalent chromium in surface treatments has been prohibited...

High cutting performance and long tool life time are the ongoing demands in the machining industry in order to increase the productivity. Hard and wear resistant coatings with superior hardness and at the same time increased toughness are required to achieve these goals. Within this work, strategies to simultaneously improve the hardness and fracture toughness of TiN based coatings grown by...

Titanium alloys and Ti-6Al-4V in particular, are widely used in the aerospace for their excellent mechanical strength to density ratio and high corrosion resistance. However, the relatively low work-hardening capabilities of these alloys compared to other metals still restricts their usage. It was recently shown that a subtransus annealing treatment followed by water quenching could generate...

The influence of grain and coherent precipitates sizes on the ductile-brittle transition temperature (BDTT) are studied in the Fe$_{78}$Al$_{10}$V$_{12}$ (A2 + L2$_1$) alloy. The alloy was produced by induction casting and followed by thermomechanical processes to obtain different precipitate and grain sizes. Further, considering the composition of the matrix phase, a single-phase...

Understanding the effects of irradiation damage from fusion reactor environments on the properties of structural materials is crucial for safe and efficient reactor design. The study of FeCr binary alloys provides fundamental insights into irradiation damage and defect behaviour without the microstructural complexities of steels.

Previous studies of irradiated FeCr have largely focused on...

Tungsten is the prime candidate for plasma-facing components in future nuclear fusion reactors because it is capable to withstand harsh operating conditions and neutron irradiation. It is known that high-energy neutrons that occur in nuclear fusion reactions change the structure of the material and its properties. In particular, they create displacement damages and transmutations. During the...

Liquid metal embrittlement (LME) is a phenomenon in which a solid metal suffers a total or partial loss of its ductility when it is under mechanical solicitation in contact with a liquid metal. The occurrence of this phenomenon depends on intrinsic factors, which are related to the nature of the metals or metallic alloys in contact; and on external factors, which are the conditions of the...

Thin film architectures often incorporate easy to fracture brittle layers for functionality. In flexible electronic applications, these brittle layers (e.g. Mo or Cr) are needed as adhesion, diffusion barrier or protective layers, while more ductile layers (e.g. Al or Cu) are deployed as conductive layers. Using dc magnetron sputtering, three thin film architectures of Mo and Al layers were...

Micro-alloyed (MA) steels are used in the automotive and energy industries for their interesting strength properties, partly due to the presence of nanometric (Ti,Nb,V)C precipitates [1].

During the welding process, there is a significant decrease in ductility of these steels in the Heat Affected Zone. Welding indeed changes the precipitation state, thereby altering the mechanical...

Duplex stainless steels (DSSs), containing bcc and fcc phase, are one of the strategically important structural materials in critical components of e.g. chemical industry, gas sector, nuclear power plants, etc. due to their excellent corrosion resistance and mechanical properties. However, the application of DSSs is limited when they are exposed to 250-500 ºC due to the separation of the...

Ti-xNb-7Zr-0.8O alloy was prepared from elemental powders by a field-assisted sintering technique (FAST). Nb is the main beta-stabilizing element, as well as being the element with the slowest diffusion. A compositional gradient of Nb was produced in the alloy, allowing the observation of phase transformations over a wide range of compositions. Scanning and transmission electron microscopy...

Zirconium and titanium are in the same group of periodic table of elements and therefore some of their properties are similar. For example, they occur in the same crystallographic structures – HCP α phase at room temperature and BCC β phase above β transus temperature. Although titanium alloys and their phase transformations have been already well-studied, zirconium alloys with higher amount...

Modifying the architecture of multilayered hard coatings used in the metal cutting industry allows to tailor the mechanical properties such as hardness or fracture toughness of these coatings. Within this work, the effect of the bilayer thickness (Λ) and the individual layer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated....

In recent years, the use of magnesium alloys in air transport has mainly been hampered by a ban on use because of its high flammability. In particular, the ban on the use of magnesium alloys on passenger seat design elements was prohibited by the Standard (AS) 8049C issued by SAE International. However, in 2015 this standard was revised and magnesium alloys meeting the flammability criteria...

Functionally Graded Materials (FGM) are materials whose composition, and hence properties, vary gradually throughout the material. These materials are commonly used as thermal barrier coatings without thermal stresses when they are required to ensure the structural integrity of components. Graded W/Cu materials, are potential candidates for the joining of the tungsten monoblocks plasma-facing...

Mechanical properties of metallic materials, such as strength and ductility, strongly depend on the microstructure. In technically pure materials, grain boundaries are the most important microstructural feature and might cause crack initiation. In molybdenum, a much used refractory metal, beside intrinsically weak interfaces, grain boundary cohesion is further influenced by impurities. Due to...

WC-Co hard metals are used in various fields, e.g. for wear protection or for metal, wood, or stone machining tools. In these applications, hard metals are exposed to different stress and temperature conditions that promote the formation of fatigue cracks and thus material failure. In this work, cyclic uniaxial tests were performed to investigate the shape changes of stress-strain hysteresis...

Additive manufacturing is used to build complex parts that are difficult to produce by conventional methods. Selective laser melting process is used to melt metallic powders layer-by-layer and form near net-shape parts. However, during the process, a large amount of powder remains unmelted. The powder is generally reused but its quality may decrease after tens of building cycles, which may...

The usual characterization of the fatigue behavior of metallic materials based on constant amplitude tests requires high experimental efforts. However, for dimensioning of highly loaded components a sound knowledge of fatigue strength as well as cyclic deformation behavior of the used material is a prerequisite. Moreover, the influence of microstructural defects, i.e., pores and non-metallic...

MYRRHA (short for Multi-purpose hYbrid Research Reactor for High-tech Applications) is a new accelerator driven system, currently under development at SCK CEN in Mol, Belgium. This nuclear system will use liquid Lead Bismuth-Eutectic (LBE) as spallation source for fast neutron production and as coolant. One of the main challenges of building MYRRHA is to find a material which can withstand the...

A good understanding of time-dependant (viscous) phenomena in materials is important for the modelling of transient and long-term behaviours of components, especially at high temperatures. Viscosity has usually been assumed to occur solely after yielding, and most high temperature constitutive models for metals are therefore designed to model elasto-viscoplastic materials. Recent work however...

The applicability of the well-known Irwin’s estimate to metals containing particles becomes dubious when the size of the plastic zone (PZ) is comparable to the particle spacing. In this work, a 3D multiscale model is used to investigate the crack tip plasticity in a cyclically loaded elastic-perfectly plastic matrix containing a realistic distribution of spherical particles. Homogenization and...

Dual-Phase (DP) steels are commonly used in the automotive industry and are known for their favorable strength and ductility. Under deformation, damage initiates in the microstructure, which is composed of relatively soft ferrite and hard martensite, in critical locations, and can propagate and coalesce until fracture occurs. Although the various types of damage and their usual initiation...

Recent developments in high temperature nanoindentation have opened the way to investigate Young’s modulus [1], hardness and creep properties [2] at very high temperature (up to 1100°C). In the meantime, Baral et al.[3] carried out in situ nanoindentation measurements at high temperature to characterize the recrystallization kinetics of a cold-rolled aluminum during annealing at 300°C....

Triboscopy is the numerical imaging of the evolution of a tribosystem and combines local and time-resolved information, most often the evolution of friction. We further developed triboscopic imaging for identifying wear mechanisms in tetrahedral amorphous carbon coatings (ta-C) during dry friction. Based on this approach we demonstrate the additional analytical opportunities enabled by this...

The paper is focused on the experimental research of the heat transfer during in-line heat treatment. Real distribution of the heat transfer coefficient (HTC) is necessary for the numerical simulation and optimization of the cooling process. The methodology proposed by the Heat Transfer and Fluid Flow Laboratory, Brno University of Technology is typically used to determine the HTC on the...

In-situ material testing in SEM is already an established technique. It can deliver unique information about the dynamic response of material under mechanical load and reveal the relationship between its macroscopic mechanical properties and microstructure. Especially when combined with further techniques such as EDS and EBSD, the response of material microstructure under load can be related...

One approach to decrease emissions and improve the efficiency of combustion engines is reducing friction losses, especially in the interface between piston ring and cylinder liner. Therefore, a new application-oriented reciprocating long-stroke tribometer at component level as well as a new multi-body system / elastohydrodynamic simulation model are evaluated by studying crank angle resolved...

In order to determine the activity of individual deformation mechanisms in a strongly textured magnesium alloy undergoing deformation, a combination of advanced in-situ and ex-situ methods was employed. Sets of samples with the orientations of normal direction (ND), rolling direction (RD), 45° between RD and ND and 30° between RD and transversal direction (TD) were machined from the rolled...

Ti6Al4V is a workhorse aerospace alloy also finding applications in the automobile, biomedical and corrosion industry due to its high specific strength, good corrosion resistance, biocompatibility, and fracture toughness. Ti6Al4V has high fracture toughness but damage micro-mechanisms during the fracture are still unexplored. In the present investigation, samples with three different...

The use of advanced aluminum alloys in the aerospace industry provides high fracture toughness, high fatigue resistance, and corrosion resistance while satisfying the need for lower structural weight [1]. Nevertheless, defects such as porosity may cause a degradation of the mechanical properties in alloys such as Al-2050. Many efforts have been made to reduce the porosity formed during casting...

Stress relaxation cracking (SRC) in austenitic stainless steels is an intergranular fracture resulting from relaxation of residual stresses introduced by welding due to further temperature exposure. This phenomenon has been associated to a residual stress threshold, the material pre-strain and grain boundary carbides. While the material damage has been observed on a macro and micro scale,...

Many metalworking tools, e.g. for milling applications, are made of hard-coated WC-Co hard metals. To date, the damage evolution in the substrate of the substrate-coating composite that leads to the loss of the coating is not completely understood. This is mainly due to the lack of material testing methods that reflect the loading conditions present near the cutting edges of milling tools,...