5.1 Materials

Doped materials and alloys, SARPES

There is a current trend towards the need for new environmentally-friendly and functional materials with tuneable properties. One unique approach combines theoretical and experimental research of novel materials with an emphasis on theoretic ab initio modelling (calculated from first principles) and electron photoemission spectroscopy (SARPES), with a particular focus on doped materials and alloys. The results will find use in applications anywhere from aerospace research to everyday consumer goods (electronics, batteries, solar cells, sensors and actuators). Because of the importance of electronics, research into the properties of materials is fundamental for both classical and molecular electronics, mechatronic systems, optoelectronics, photonics and spintronics.

Competencies and provided expertise:

• Measurements of the electron structure of solids using the experimental method of angle-resolved photoemission spectroscopy (ARPES) of the valence band and internal electrons (XPS).
• Experimental and theoretical research into the spin and electron properties of materials depending on changes to the chemical composition and doping of alloys.
• The affectability and tuning of the properties of material nanostructures due to seemingly small changes to their size, shape and chemical composition (electronic, magnetic and optical properties on a broad scale).
• Experimental and theoretical calculations focused on microscopic processes at a quantum-mechanical level, mechanical properties such as strength and elasticity described at the level of classical molecular dynamics or continuum mechanics.
• A focus on spintronic, photovoltaic and superconducting materials and alloys.
• Characterisation of the links between the properties of materials used in sensors and their electron structure, the prediction and control of these properties.
• SPRKKR software tools intended for material research (the interpretation of experiments, predictive model calculations of the properties of newly prepared materials) in the field of alloys, magnetism, spectroscopy and spintronics.

Advanced polymer composite materials

Polymer composite materials based on synthetic polymer matrices reinforced with glass and carbon fibres are still commonly used primarily in automotive and aeronautical applications (when building light frames with significant reductions in material use and weight), but also have a place in the medicine, sports and consumer goods industries. This is mainly due to their physical, mechanical and chemical properties. The disadvantage is in how difficult they are to recycle and upcycle, as well as their negative environmental impacts. For this reason, there is a growing prominence of biodegradable polymer composite materials, using both fibrous fillers, but also differential structures and particles from nanoscopic to large-scale 3D shapes, often subject to further structural or surface modification. One topical subject is the application of nanofillers (particles, fibres, yarns) and nanostructures, or more precisely the process of their adaptation into polymer matrices. These are used in the design, construction and production of technical parts due to their specific modifiable properties (type of matrix, type, shape and size of filler; modification of filler and interphase interface), taking into account the required final properties of the given part. Such materials have relevant uses in practically all branches of industry, from engineering to medicine, including material composition for additive technologies.

Competencies and provided expertise:

• Expertise in the field of synthetic and biodegradable polymer composites, from material composition to the evaluation of specific properties, degradability and environmental impact (preparation of concentrated masterbatches, the collection and processing of rheological data and process values).
• Preparation of next-generation fillers for composite systems.
• The process of nanofiller application (particles, fibres, yarns) and nanostructures, the process of nanofiller and nanostructure alterations and modifications into biopolymer matrices.
• Specific design of the material composition of composite systems, research into the influence of matrix type on composite properties; influence of the size, shape, type and orientation of filler on composite properties; influence of filler modifications on the interphase interface and resulting properties.
• Conditions for the application of nanostructural, nanofibrous and 3D structures and fillers, porous structures and substitutional materials.
• Determination of the properties of composite materials in relation to material composition and type of components; evaluation of morphology and properties according to application; evaluation of surface quality for subsequent additional technological operations.
• Evaluation of aging and degradation of polymer composites; recycling and upcycling of composites, evaluation of environmental impacts (UV stability, aerobic and anaerobic biodegradation – industrial composting, wastewater treatment plants, landfills and biogas plants).
• Evaluation of application potential; monitoring of processing parameters according to the choice of processing technology; possibilities for industrial use from additive technologies to the manufacturing industry.

Powder metallurgy

Powder metallurgy is a modern and rapidly developing additive technology for the processing of metal structural and functional materials. The increasing interest in these techniques is mainly due to their potential for alloy preparation, which are usually characterised by an ultrafine-grained nanocrystal or amorphous microstructure, while simultaneously increasing the solubility of alloying elements. In contrast to conventional methods of preparing materials for technological processes of casting and subsequent appropriate thermal or thermomechanical processing, powder metallurgy offers a number of possible advantages. Some examples include the preparation of precisely shaped products, the production of composite materials, the production of materials with controlled porosity (“metal foams”) or the preparation of materials with high melting points that are otherwise practically impossible to produce using classical metallurgical processes. Novel functional materials, such as alloys characterised by a combination of high strength and malleability and excellent heat resistance, are finding applications in a number of places in the automotive, energy and aerospace industries. There is also a promise in the development of materials for medical applications (biocompatible substitutes).

Competencies and provided expertise:

• The preparation of unique materials with an exceptionally fine-grained microstructure and presence of unbalanced phases, the preparation of materials with controlled porosity, the preparation of materials with high melting temperatures or special optical properties, which cannot be prepared with other technologies.
• The preparation of high-entropy cobalt or aluminium-based alloys, the compaction of titanium alloys, the preparation of intermetallic phases and metastable structures, the compaction of ceramic materials from fine-grained nanopowders and the preparation of magnesium or zinc-based biodegradable materials.
• Mechanical alloying processes, where alloysin powder form prepared with high effectivity and minimal contamination with the material of the grinding vessels.
• Material compaction using plasma sintering technologies (SPS). The prepared compact samples have an average size from 20 to 50 mm, placing the device on the boundary between laboratory and pilot plant machines.
• The preparation of Fe-Al-Si, Ti-Al-Si and Ni-Ti alloys made up of mostly intermetallic phases by a combination of mechanical alloying and SPS.
• Research into new materials for medical applications, oriented towards the preparation and study of composite materials with a magnesium matrix and reinforced with hydroxyapatite and other phosphates, magnesium fluoride and porous materials.
• Biodegradable alloys on a zinc basis with optimised corrosive, mechanical and biological properties.
• Processing of innovative iron-based intermetallics using mechanical alloying and plasma sintering.
• Preparation of NiTi shape-memory alloys using reactive sintering.
• Novel metallurgical processes for new “natural alloys”.
• Micro- and nanocrystal materials with a high interface proportion for modern structural applications, biodegradable implants.

Structural and functional materials

The structural elements of various engineering and energy applications necessitate a given combination of strength and plastic parameters of the utilised materials. This makes it essential to develop deformation simulations and mathematical and computational methods in the area of bulk deformation (constitutive modelling, calculations of activation energy during hot forming, etc.). Powder technologies allow for the development of materials with unique properties, such as friction composites and sliding materials, porous materials, magnetic materials, diamond-based abrasive and cutting materials. Part of this includes solving areas of thermophysical, thermodynamic and kinetic behaviour of the materials being developed in their solid or liquid phase (melts) based on temperature, time and other parameters, while taking into account knowledge of the mechanisms of the surrounding processes (phase transformations, sintering, etc.). The results of the development of the aforementioned expertise are used to optimise existing process technologies or introduce new materials and technologies based on an understanding of the deformation behaviour of materials. A key application in areas of powder technologies is the control and regulation of the emission of nano- and micrometre-sized abrasive particles from friction composites for braking systems of cars or new materials for diamond abrasion/cutting tools for the machining of hard workpieces, or of materials such as cemented carbides, glass, ceramics, sapphires, semiconductors and others.

Competencies and provided expertise:

• Experimental simulation of deformations during bulk forming (constitutive modelling of deformation resistances, temperature, ductility, etc.).
• Material properties of continuous casting. Determination of temperature and speed trends in formability.
• Mathematical description of reinforcing and curing processes based on properties of the initial microstructure.
• Determination of activation energy during hot forming in various phase areas (SW ENERGY 4.0).
• Optimisation of bulk deformation parameters as a result of controlled structure-forming processes.
• Prediction of the energy-power parameters of deformation, based on models of natural deformation resistance developed for a broad range of thermomechanical deformation conditions.
• Optimisation of the cooling parameters of hot formed products based on experimentally completed (D)CCT decay diagrams.
• The design and study of new materials exhibiting optimal friction-abrasion properties to monitor the level of abrasion in friction materials (automotive brake pads).
• Research into the composition and conditions for the sintering of diamond abrasion and cutting materials.
• Determination of the effectiveness of grinding and cuts made by diamond abrasion and cutting wheels on actual CNC machine tools.
• Study of the diffusion processes and phase transformations during the sintering process, structural characteristics and phase composition.
• Use of hydride or hydrogenated compound alloying technologies in the area of waste magnet recycling.
• Thermal analysis of developed materials.

Innovative steel materials and technologies for specific applications

Modern innovative materials also include various types of steel. In the automotive industry, these are mainly multi-phase steels using various reinforcement mechanisms such as TRIP, TWIP, dual phase, QP, low-to-medium manganese steels as well as precipitation-hardened maraging steel. Apart from the development of these materials, including appropriate alloying to ensure the required mechanical properties, it is also necessary to develop unique processing technologies, especially concerning the economic demands of the entire process. A typical example of this development are PH steels prepared using press hardening technology. Another special group of steels are so-called ODS steels, which utilise Al and Y-based nano-oxide dispersion strengthening and are primarily used in high-temperature applications, thanks to their excellent creep properties. Achieving unique mechanical and functional characteristics of the resulting parts and components while concurrently increasing production efficiency and introducing new processes and technologies (material-technological modelling, hot-rolling of wire rods, stabilisation annealing in austenitic stainless steel used in nuclear power production, etc.) is a requirement for the possible uses of specific applications in the aerospace or automotive industry and in process technologies.

Competencies and provided expertise:

• Design of new steels for specific uses.
• Research into the influence of heat treatment parameters on microstructure and properties.
• Research into phase transformations during thermal or thermomechanical processing.
• Research into mechanisms of steel reinforcement.
• Research into material behaviour during thermal or mechanical load using in-situ techniques; local characterisation of mechanical properties.
• Production of rotary intermediate products  from modern materials (using low and medium manganese high-strength multi-phase steels, diffusion bonding of two different materials during the rolling process, production of strengthened intermediate products from maraging steels).
• Optimisation of actual processing technologies using material-technological modelling (for example to increase heat treatment process efficiency during forging, rolling, etc.).
• Hot stamping technology – use of a heated tool for an omega profile in order to verify and optimise the processing conditions of various materials.
• Improving the mechanical and functional characteristics of tool steels.

Characterisation of metal materials using miniature samples.

Evaluation of the mechanical properties of not only metal materials is a necessary standard procedure for the proper design and use of structural materials. When assessing the optimal properties of the whole (part or components), a broader range of mechanical tests is always necessary to achieve a detailed characterisation of material properties. The traditional approach to characterisation makes use of “large samples”; however, this method is often limited by the lack of available experimental samples, for example the assessment of local properties with high change-gradients, on components being operated, and with functionally graduated materials, or materials produced using special techniques (intensive plastic deformation, additive methods). In the cases where non-destructive methods cannot be carried out, or are not economically viable, the use of miniature testing specimens appears promising. This developed method allows for the complex characterisation of the mechanical properties of metal materials, and is used in the production of material models of local areas, the development of thermal and thermomechanical processing methods, of materials prepared using methods of intense plastic deformation or by additive methods.

Procedures for the miniaturised test specimens:

• Tensile testing under room-temperature and quasi-static load conditions.
• Dynamic tensile testing up to deformation speeds in orders of 1000s–1.
• Tensile testing under reduced or increased temperatures (from -150°C to 1400°C), including increased deformation speeds.
• Notch toughness tests, including a determination of transition temperature.
• Fracture mechanics testing – J-R curves, master curves.
• Fatigue crack growth testing including determination of values of threshold stress intensity factors.
• Low-cycle and high-cycle fatigue testing, including at increased and decreased temperatures.
• Creep tests.
• Evaluation of plasticity area and damage.