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

The strain induced decomposition of the supersaturated solid solutions of Al30Zn2Cu and Al10Zn2Cu (wt.%) alloys was investigated thanks to X-ray diffraction and transmission electron microscopy. Solutionized materials were deformed at room temperature by high pressure torsion and the large plastic strain led to a concomitant grain refinement and decomposition of the supersaturated solid...

Severe plastic deformation (SPD) leads not only to strong grain refinement and material strengthening but also can drive phase transformations. The fundamentals of the α→ω and β→ω phase transformations in Ti-Co, Ti-Nb and Ti-Ni based alloys induced by high pressure torsion (HPT) at the same conditions depending on the amount of the β-alloying elements were studied. Scanning electron...

Many leading laboratories worldwide are currently using high pressure torsion (HPT) as a method for creating new materials by mixing metallic components in solid state. At the initial stage of deformation, mechanical mixing is carried out exclusively by changing the shape of the constituent components without any interaction between them at the atomic level. This mechanical mixing is called...

High pressure torsion (HPT) as a means of grain refinement to the nanoscale has been well-explored since Percy Bridgman's early physics experiments in the early 1900s. More recent studies continue to make strides in our understanding of the processing-to-property relationships of nanocrystalline materials, but the role of the applied pressure has received less attention, especially in the case...

The concept of a combination of severe plastic deformation and precipitation hardening has been studied as a desired route for further mechanical performance improvement of ultrafine grained materials. However, deformation induced defects suppress the nucleation of strengthening phases in most cases. On the other hand, thermal instabilities of severely deformed aluminum alloys exclude...

The present study investigates the effect of room temperature high pressure torsion (HPT) processing of pure Nb, Nb-1Zr (wt.%) and Nb-1Zr-0.1C (wt.%) on the microstructure, texture and mechanical property evolution. Being a ductile BCC material, and due to the application of a high hydrostatic pressure, the disk-shaped samples deformed without the formation of microcracks. X-ray line profile...

In recent years the uncommon behaviour of nanocrystalline systems to increase in hardness or plastic yield onset upon annealing treatments has been observed more and more frequently. This is counterintuitive to the common argument that heat treatments lead to changes which would decrease any resistance to plastic flow, e.g. decrease in dislocation density, increase in grain size, growth of...

The processing of heterogeneous grain microstructures is a strategy that is commonly used in metallurgy to face the strength-ductility trade-off dilemma. The harmonic concept was first developed by Pr. Ameyama et al. on several metallic materials, including steel [1], CP titanium, and α/β titanium alloys [2], which all show good mechanical behaviors when harmonic-structured. This study applied...

Pearlite is a lamellar composite microstructure that enhances the strength of steel while preserving its ductility. One of the prominent applications of pearlite in tribology is in the rail-wheel system. However, due to high contact pressures, the cyclic plastic deformation leads to the formation of the brittle nanostructured white etching layer (WEL) [1].

The pearlite microstructure...

It is known that fine-grained and equiaxed microstructure of two-phase titanium alloys enables superplastic behavior, which is the ability of a material to exhibit large plastic deformation at high temperature and a specific strain rate without necking. One of the main challenges of superplastic forming is to improve its technological and financial efficiency by lowering the forming...

Severe plastic deformation (SPD) processes like High pressure torsion (HPT) enable the production of nanocomposite materials. When applied to powder blends of permanent magnetic phases like SmCo$_5$ and binder metallic phase such as Cu, it opens up a new route for the production of novel magnetic materials. HPT of powder blends thus enables a nearly free selection of the magnetic phase and the...

High pressure torsion(HPT), a method of severe plastic deformation(SPD) was initially used by Bridgman to get deeper insights into geological and mineralogical processes. HPT has unique process conditions and enables scientists to study bulk specimens of normally rather difficult to deform materials like oxides, ceramics, glasses, etc. For oxides in particular, HPT is capable of influencing...

Ultrafine grained (UFG) or even nanocrystalline (NC) materials feature interesting functional properties due to their refined microstructure. Focussing on magnetic properties, strong microstructural influences can e.g. be found for the coercive field dependence or the occurrence of exchange coupling phenomena between phases of different magnetic properties. As it is well known, severe plastic...

It is known for almost two decades that grain boundaries in nanostructured metals are not static objects but can migrate during loading. This has been evidenced for almost any loading situation ranging from indentation to fatigue testing and from cryogenic to moderately enhanced temperatures. Certainly such structural instabilities can drastically affect the mechanical performance and an...

The present study investigates the impact of stacking fault energy on the microstructure evolution and mechanical properties of nanostructured metals that differ in stacking fault energy, annealed under high hydrostatic and atmospheric pressure. Ag and Ni were selected as materials of low and high stacking fault energy, respectively. To this end, nanostructured metals were obtained by high...

Although a number of SPD processing techniques is now available, high-pressure torsion (HPT) is an especially attractive, because it leads to exceptional grain refinement. It was widely used to process various metals and their alloys. Recently, a new approach was set to fabricate a metal matrix nanocomposite (MMNC) by HPT processing two or more various commercial metal disks. This...

Accumulative roll bonding (ARB) was first introduced by Saito et al. in 1998 [1]. In recent years, this process was used to produce ultrafine-grained (UFG) multilayered laminates out of a variety of material combinations [2]. Laminated metal composites (LMCs) can be tailored towards the exhibition of a variety of extrinsic toughening mechanisms and thus show promising potential for...

Since the beginning of systematic materials science, researchers have been aiming to combine high strength with ductility, maximizing the overall mechanical performance and damage tolerance of a material. The well-known strength-ductility paradigm makes it impossible to achieve these properties in a homogeneous material. However, heterogeneous materials, such as nanocomposites, are a promising...

The Accumulative Roll Bonding (ARB) process is well known for producing ultrafine-grained structures with remarkable material properties compared to conventionally produced sheet material [Saito1998]. Additionally, manifold tailoring possibilities by combining different metallic materials into so-called laminated metallic composites (LMCs) open a broad potential to produce new advanced sheet...

The study concerns formability and ductility of UFG plates made of commercial aluminum alloys 3003 and 5754 processed by ECAP-based methods, i.e. Incremental ECAP and multi turn ECAP followed by upsetting. It is demonstrated that the processes result in UFG microstructure with high fraction of high angle grain boundaries exceeding 60% and fairly uniaxial grain of equivalent diameter below 600...