Search results for: R. Kawalla

Items from 1 to 20 out of 39 results

article

Investigation of Plastically Deformed TRIP-Composites by Neutron Diffraction and Small-Angle Neutron Scattering Methods

G. D. Bokuchava, Yu. E. Gorshkova, I. V. Papushkin, S. V. Guk, more

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques > 2018 > 12 > 2 > 227-232

The main parameters of the microstructure of TRIP (TRansformation Induced Plasticity) composites with an austenitic matrix and a ZrO₂ zirconium-dioxide reinforcing phase subjected to plastic deformation of different degrees (compressive uniaxial load) are studied by neutron diffraction and small-angle neutron scattering. A series of composite material samples with different contents of the ZrO₂ ceramic...

article

Hot Roll Bonding of Aluminum to Twin-Roll Cast (TRC) Magnesium and Its Subsequent Deformation Behavior

H. Saleh, M. Schmidtchen, R. Kawalla

Journal of Materials Engineering and Performance > 2018 > 27 > 10 > 5069-5078

In an experiment in which twin-roll cast AZ31 magnesium alloy and commercial purity aluminum (AA 1050) sheets were bonded by hot rolling as Al/Mg/Al laminate composites, it was found that increasing the preheating temperatures up to 400 °C enhances the bonding strength of composites. Further increases in the preheating temperatures accelerate the magnesium oxide growth and thus reduce the bonding...

article

Effect of Biaxial Isothermal Quasi-Continuous Deformation on Structure and Shape Memory Properties of Ti-Ni Alloys

I. Khmelevskaya, V. Komarov, R. Kawalla, S. Prokoshkin, more

Journal of Materials Engineering and Performance > 2017 > 26 > 8 > 4011-4019

Severe plastic deformation (SPD) of Ti-50.0 at.% Ni alloy was carried out using the multi-axial deformation MaxStrain module of Gleeble system at 400, 370, 350 and 330 °C with accumulated true strains from e = 3.5 to 9.5. Kinetics of martensitic transformations was studied by DSC method, the structure features by x-ray diffraction and TEM. The recoverable strain was studied using a bending mode for...

article

Numerical Investigation of the Oxide Scale Deformation Behaviour with Consideration of Carbon Content during Hot Forging

B.-A. Behrens, R. Kawalla, B. Awiszus, A. Bouguecha, more

Procedia Engineering > 2017 > 207 > C > 526-531

Due to increasing product requirements the numerical simulation has become a powerful tool for the effective and efficient design of individual process steps as well as entire process chains. In order to model hot forging processes with finite element based numerical methods realistic models are required which consider the detailed mathematical description of the material behaviour during the forging...

article

Evolution and Interaction of the Microstructure and Texture at the Different Processing Steps for Ferritic Nonoriented Electrical Steels

J. Schneider, A. Franke, A. Stocker, H.-T. Liu, more

IEEE Transactions on Magnetics > 2016 > 52 > 5-1 > 1 - 6

The fabrication process of nonoriented electrical steels comprises casting, hot rolling, cold rolling, and final annealing. The development of new technologies for the fabrication of hot band offers new possibilities. In this paper, we will shortly describe the similarities and differences with respect to the evolution of microstructure (grain structure) and texture along the conventional processing...

article

Effect of the Interdependence of Cold Rolling Strategies and Subsequent Punching on Magnetic Properties of NO Steel Sheets

S. Steentjes, N. Leuning, J. Dierdorf, X. Wei, more

IEEE Transactions on Magnetics > 2016 > 52 > 5-1 > 1 - 4

Nowadays, optimization of non-oriented (NO) electrical steels toward lower iron-loss, improved, and isotropic magnetizability is critical to the improvement of rotating electrical machines. The whole production process chain adjusts the microstructure evolution, e.g., grain size and crystallographic texture, determining the magnetic properties. In particular, the interdependence of raw material properties...

article

Drawability Studies of Magnesium Alloy Sheets at Elevated Temperature

M. Hyrcza-Michalska, R. Kawalla, J. Dembińska

Archives of Metallurgy and Materials > 2015 > Vol. 60, iss. 4 > 2751--2756

The paper presents the results of a study of drawability of thin AZ31 magnesium alloy metal sheets. These studies are a continuation of experiences in presenting the characteristics of technological plasticity of strips made of magnesium alloy which have been cast between rolls in vertical and horizontal systems called ‘twin-roll casting’. In the context of previous experiments conducted at the Institute...

article

Property-oriented Production of Forged Magnesium Components

M. Graf, M. Ullmann, R. Kawalla

Materials Today: Proceedings > 2015 > 2 > Supplement 1 > S76-S84

The significance of light-weight construction in the automotive industry continues to increase. The reasons for this lie, for example, in the reduction of CO ₂ emissions achieved by fuel savings due to reductions in automobile weight. Low vehicle weights can be achieved through material substitution or improved topologies. Steel, however, remains the most commonly used material for the manufacture...

article

Effect of Grain refining Additives on Microstructure and Mechanical Properties of the Commercial Available Magnesium alloys AZ31 and AM50

K. Neh, M. Ullmann, R. Kawalla

Materials Today: Proceedings > 2015 > 2 > Supplement 1 > S219-S224

In order to fulfill the requirements of lightweight design, the establishment of magnesium wrought alloys is an important issue. To achieve this aim the development of new alloy compositions is essential. Therefore, the influence of different additives to commercial available magnesium alloys (AZ31, AM50) on microstructure and mechanical properties is investigated in this work. After casting of the...

article

Anisotropy of the Mechanical Properties of Twin-roll Cast, Rolled and Heat-treated AZ31 as a Function of Temperature and Strain rate

F. Berge, L. Krüger, M. Ullmann, C. Krbetschek, more

Materials Today: Proceedings > 2015 > 2 > Supplement 1 > S233-S241

The influence of temperature on the mechanical properties of twin-roll cast, rolled and heat-treated AZ31 was investigated under tensile loading from different directions (0°, 90). Therefore, quasi-static tensile tests with a strain rate of 0.76×10 ⁻³ s ⁻¹ , 0.73×10 ⁻² s ⁻¹ , and 0.72×10 ⁻¹ s ⁻¹ were performed with an electromechanical universal testing...

article

Twin Roll Casting and Strip Rolling of Several Magnesium Alloys

K. Neh, M. Ullmann, M. Oswald, F. Berge, more

Materials Today: Proceedings > 2015 > 2 > Supplement 1 > S45-S52

The twin roll casting (TRC) process enables the production of magnesium strips in an economic way. In combination with strip rolling, magnesium flat products with a great potential for industrial applications are produced. Current achievable mechanical properties of strips made of several magnesium alloys, produced by twin roll casting and subsequent strip rolling, are shown in this work. Therefore,...

article

Static Recrystallization Kinetics of a Twin-roll Cast AZ31 alloy

M. Ullmann, M. Graf, R. Kawalla

Materials Today: Proceedings > 2015 > 2 > Supplement 1 > S212-S218

The static recrystallization (SRX) behaviour of twin-roll cast and annealed magnesium AZ31 strip during hot deformation was determined under deformation conditions corresponding to the hot strip rolling process used in the production of twin-roll cast magnesium coils. Plane strain compression tests were performed using double-hit schedules at temperatures of 250°°C°–°400°°C, strain rates of 1°s ...

article

Concept of thermal modelling for hot strip rolling of magnesium

A. Nami, U. Prüfert, M. Eeiermann, R. Kawalla

Computer Methods in Materials Science > 2015 > Vol. 15, No.1 > 23--29

The paper introduces a concept for the reversing hot rolling of magnesium strip consisting of reheating of twin roll casted rough strip, carrying of coil from a furnace to coiler, setting down on mandrel, uncoiling, hot rolling and coiling of the magnesium strip. In the first stage the thermal models should be established. These models shall serve in the subsequent stages in order to support by developing...

article

Optimization and application of GPU calculations in material science

G. Korpała, R. Kawalla

Computer Methods in Materials Science > 2015 > Vol. 15, No.1 > 185--191

Modern Graphic Processing Units (GPU) provide in combination with a very fast Video Random Access Memory (VRAM) very high computational procedure, outrunning the conventional combination of a Central Processing Unit (CPU) and Random Access Memory (RAM) in terms of parallel computing and calculation. Within this work a concept for parallel application of the CPU/GPU is presented which combines the...

article

Microstructure evolution in warm forged sintered ultrahigh carbon steel

S. Szczepanik, P. Nikiel, S. C. Mitchell, R. Kawalla

Archives of Civil and Mechanical Engineering > 2015 > Vol. 15, no. 2 > 301--307

Fe–1.4C–0.65Si–0.85Mo ultrahigh carbon steel was liquid phase sintered in 10%H2–90%N2 at 1300 °C from Höganas Astaloy 85 Mo HP base iron, fine graphite and silicon carbide powders mixed with polypropylene glycol. The microstructure then comprised fine pearlite and grain boundary cementite networks and the density increased from ∼6.8 g cm−3 to ∼7.7 g cm−3. A group of specimens then underwent austenitisation,...

article

Quantifying texture evolution during hot rolling of magnesium Twin Roll Cast strip

S. Gorelova, H. Schaeben, R. Kawalla

Materials Science & Engineering A > 2014 > 602 > Complete > 134-142

Multi-pass rolling experiments with an AZ31 Twin Roll Cast (TRC) alloy were performed on an industrial scaled four-high rolling mill. During rolling with an intermediate annealing the evolution of texture and microstructure was investigated. To quantify the extent of preferred crystallographic orientation experimental X-ray pole figures were measured after different process steps and analyzed using...

article

Dynamic recrystallisation and precipitation behaviour of high strength and highly conducting Cu–Ag–Zr-alloys

F. Bittner, S. Yin, A. Kauffmann, J. Freudenberger, more

Materials Science & Engineering A > 2014 > 597 > Complete > 139-147

Dynamic recrystallisation of CuAgZr alloys within a composition range of (3–7)wt% Ag and (0.05–0.3)wt% Zr is studied as a function of alloy composition, temperature and strain. Dynamic recrystallisation was investigated using hot-compression and hot-rolling experiments at temperatures between 500°C and 850°C. For CuAgZr with 7wt% Ag and 0.05wt% Zr, an optimised hot-rolling temperature of 750°C was...

article

Production of auto-body dual-phase steel with single-step cooling on the output conveyer of the 2000 continuous broad-strip mill at OAO NLMK

A. S. Tataru, V. K. Potemkin, R. Kawalla, A. S. Lukin, more

Steel in Translation > 2014 > 44 > 7 > 491-497

The goal is to produce hot-rolled dual-phase steel of strength class DP 450–600 at OAO Novolipetskii Metallurgicheskii Kombinat (NLMK). The steel’s final structure and properties is greatly affected by single-stage strip cooling on the output roller conveyer of the 2000 continuous broad-strip mill. The influence of the hot-rolling parameters on the structure and mechanical properties of the hot-rolled...

article

An XPS Study of Native Oxide and Isothermal Oxidation Kinetics at 300 °C of AZ31 Twin Roll Cast Magnesium Alloy

H. Saleh, T. Weling, J. Seidel, M. Schmidtchen, more

Oxidation of Metals > 2014 > 81 > 5-6 > 529-548

Magnesium alloys are very important for lightweight applications. Industrially, these alloys cannot be used without some necessary processing to improve their corrosion properties. The most widely used methods include coating, surface treatments and cladding. In these processes, the magnesium oxide scale plays an important role in the bonding mechanism between the substrate and the coating or the...

article

Thermal Modelling for Production of Hot Strip of Magnesium Alloy

A. Nam, U. Prufert, R. Kawalla

Journal of Machine Engineering > 2014 > Vol. 14, No. 1 > 29--38

The paper deals with a thermal modelling of a magnesium coil in the magnesium strip production. The magnesium coil heating is the preparation step for the magnesium hot strip rolling and occurs in the special air circulating furnace. The cooling of the coil takes place on the several steps such as a transport of coil after heating from the furnace to a mill coiler. The aim of the work is to develop...

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INFONA - science communication portal

Search results for: R. Kawalla

Investigation of Plastically Deformed TRIP-Composites by Neutron Diffraction and Small-Angle Neutron Scattering Methods

Hot Roll Bonding of Aluminum to Twin-Roll Cast (TRC) Magnesium and Its Subsequent Deformation Behavior

Effect of Biaxial Isothermal Quasi-Continuous Deformation on Structure and Shape Memory Properties of Ti-Ni Alloys

Numerical Investigation of the Oxide Scale Deformation Behaviour with Consideration of Carbon Content during Hot Forging

Evolution and Interaction of the Microstructure and Texture at the Different Processing Steps for Ferritic Nonoriented Electrical Steels

Effect of the Interdependence of Cold Rolling Strategies and Subsequent Punching on Magnetic Properties of NO Steel Sheets

Drawability Studies of Magnesium Alloy Sheets at Elevated Temperature

Property-oriented Production of Forged Magnesium Components

Effect of Grain refining Additives on Microstructure and Mechanical Properties of the Commercial Available Magnesium alloys AZ31 and AM50

Anisotropy of the Mechanical Properties of Twin-roll Cast, Rolled and Heat-treated AZ31 as a Function of Temperature and Strain rate

Twin Roll Casting and Strip Rolling of Several Magnesium Alloys

Static Recrystallization Kinetics of a Twin-roll Cast AZ31 alloy

Concept of thermal modelling for hot strip rolling of magnesium

Optimization and application of GPU calculations in material science

Microstructure evolution in warm forged sintered ultrahigh carbon steel

Quantifying texture evolution during hot rolling of magnesium Twin Roll Cast strip

Dynamic recrystallisation and precipitation behaviour of high strength and highly conducting Cu–Ag–Zr-alloys

Production of auto-body dual-phase steel with single-step cooling on the output conveyer of the 2000 continuous broad-strip mill at OAO NLMK

An XPS Study of Native Oxide and Isothermal Oxidation Kinetics at 300 °C of AZ31 Twin Roll Cast Magnesium Alloy

Thermal Modelling for Production of Hot Strip of Magnesium Alloy

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