
Ulrich PrahlTU Bergakademie Freiberg · Institute of Metal Forming
Ulrich Prahl
Dr.-Ing. Dipl.-Math.
About
382
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Introduction
My interest is on the forming and material technology development for metals by applying experimental as well as numerical simulation. I study microstructure evolution and properties of steels and metallic materials during forming, processing and manufacturing. I apply microstructure-based modeling and characterisation of process chains for the prediction of material flow as well as of the evolution of precipitations and microstructure. I use combined lab experiments plus thermodynamic-kinetic and thermomechanical approaches for the quantitative correlations of microstructure and mechanical properties towards a systematically design of alloys and processes.
Additional affiliations
October 2017 - present
February 2002 - September 2017
Publications
Publications (382)
This study investigates the influence of heat treatment and hot rolling on the microstructure and texture development of the magnesium alloy Resoloy ® , which was specifically designed for biomedical applications. The alloy was subjected to various heat treatment conditions (375 °C to 500 °C for 15 min to 6 h) and subsequently hot-rolled at equival...
A novel approach was proposed, based on the application of the fuzzy logic (FL) method for the fast analysis of the hot deformation process of 80MnSi8-6 steel. In the first stage, the curves developed from plastometric tests and the results of studies of the microstructure of the deformed samples were used as input data for the analysis. Input and...
In this work, ceramic particle and metal matrix interfacial delamination in transformation-induced plasticity steel composite reinforced with magnesium partially stabilized zirconia particles is investigated using a parametric modeling approach. The global behavior of the composite is modeled using elastic and Johnson-Cook plasticity models for the...
This article provides a comparative characterization of the mechanical and technological properties of a modified 20MnB4 quenched and tempered steel that are important for further processing. The aim of the modification was to represent the steel as a secondary steel with a significantly increased holding of accompanying elements to be assumed in t...
The hydrogen embrittlement behavior of a prerolled Fe–15Mn–0.65C–2Al–2Si high‐Mn steel with various cut‐edge properties is studied via hydrogen precharging and slow strain rate test. In the presence of hydrogen, samples prepared by laser cutting under atmosphere of N 2 exhibit the best total elongation at about 39%. Press blanking produces severe s...
The twin-roll casting (TRC) of light metal alloys, in particular aluminium and magnesium alloys, represents a promising technology for the production of lightweight components thanks to its short process chain and promising combinations of properties. In the production of strip products, TRC is susceptible to a number of defects due to the coupled...
This collection of papers entitled "Process-structure–property relationship of lightweight metallic materials" brings together a selection of advanced research papers that focus on the multifaceted relationships between processing methods, microstructural evolution, and the resulting thermomechanical properties of lightweight metallic materials. Un...
Twin-roll casting (TRC) of magnesium sheets has already been analysed in numerous ways. The installation of a pilot plant for the twin-roll casting of magnesium wire at the Institute of Metal Forming, TU Bergakademie Freiberg, has opened up a further area for research. The principle of twin-roll casting of wire is comparable, although the microstru...
This study introduces the ZAX210 magnesium alloy wire, produced using groove rolling. The starting material, initially extruded, was successfully rolled from 12.0 mm to 6.7 mm diameter in eight passes using square-oval grooves, finishing with an oval and round shape. High strain rates and an optimized rolling temperature of 265 °C were found benefi...
Accumulative roll bonding (ARB) is a repeated cladding process in which two or more sheets of material are joined together by rolling at temperatures below recrystallization. The present review is focused on ARB of high‐alloy steels, which, among other laminated metal composites (LMCs), deliver the highest mechanical properties. After a brief descr...
This study investigates tensile deformation, damage analysis, and the effect of microtexture on a 10 % vol. zirconia particle-reinforced TRIP steel composite. In situ tensile tests and simulations were conducted, with sequential SEM images captured during tensile loading tests and electron backscatter diffraction (EBSD) providing initial crystal or...
This study investigates deformation, interfacial, and particle damage in a magnesium-partially stabilized zirconia (Mg-PSZ) particle-reinforced transformation-induced plasticity (TRIP) steel composite using SEM in situ tensile tests and finite element simulations. The simulation models employ an elastic model for ceramic particles and a Johnson-Coo...
The addition of alloying elements is a crucial factor in improving the mechanical properties of pure copper, particularly in terms of enhancing its yield strength and hardness. This study examines the influence of scandium additions (up to 0.27 wt.%) on low-alloyed copper. Following the casting and solution-annealing processes, the alloys were quen...
This study investigates the microstructural behavior of laboratory-produced Al–Mg–Si(X)–Mn aluminum alloys, focusing on the influence of varying Si content during biaxial hot tensile testing. Alloys with Si contents of 0.7%, 0.9%, and 1.3% were subjected to biaxial deformation at temperatures of 200 °C, 300 °C, and 400 °C. Using digital image corre...
In this study, we quantitatively investigate the impact of 1.4 wt.% chromium and 1.4 wt.% molybdenum additions on pearlitic microstructure characteristics in 1 wt.% carbon steels. The study was carried out using a combination of experimental methods and phase field simulations. We utilized MatCalc v5.51 and JMatPro v12 to predict transformation beh...
Conventionally used brass alloy CuZn30 shows problems with corrosion resistance in the form of dezincification when used in brass instruments. Therefore, within the scope of this investigation, a new brass alloy CuZn30 is developed in the microalloy range with corrosion-free or corrosion-inhibiting properties. First, the influence of microalloying...
In this work, the microstructural deformation and damage mechanisms of TRIP steel metal matrix composites (MMCs) reinforced with Magnesia Partially Stabilized Zirconia (Mg-PSZ) particles are investigated by employing in situ tensile testing within a scanning electron microscope chamber, complemented by digital image correlation and advanced image p...
Due to the growing interest in lightweight constructions, the continuous casting of nonferrous metals is continuously developing as a result of the cost-effectiveness of this process, which combines several stages of sheet production. Unfortunately, because of the characteristics of the process, the parameters in the roll gap, such as, for example,...
The microstructure evolution during hot deformation of 80MnSi8-6 nanobainitic steel was investigated through hot compression tests at deformation temperatures of 900–1250°C and strain rates of 0.1–20 s ⁻¹ . The flow curves revealed strain-hardening behavior at the beginning of deformation followed by softening effects caused by microstructure evolu...
This study explores the intricate interplay between strain-induced precipitation (SIP) and the underlying mechanisms that govern hot deformation in AA6082 aluminum alloy. Uniaxial tensile tests were conducted at elevated temperatures, ranging from 200 °C to 400 °C, and varied strain rates from 0.01 s-1 to 10 s-1. Employing advanced methodologies su...
The use of aluminum alloys in conjunction with thermal-assisted forming techniques permits the production of
high-strength and geometrically complicated components without failure. By using innovative, temperaturedependent
production techniques, it is possible to manufacture components with tailored properties. So far,
however, it is not possible t...
This research provides a comprehensive analysis of the texture and temperature dependent deformation behavior of the aluminum alloy AA6082. The study is performed using a combination of experimental deformation tests and computational simulations based on a crystal plasticity (CP) framework. The primary objective is to identify the critical influen...
Copper alloys containing chromium and hafnium combine elevated mechanical strength and high electrical and thermal conductivity. For the simultaneous enhancement of both material properties, precipitation hardening is the utilized mechanism. Therefore, the aim is to analyze the influence of chromium and hafnium in binary and ternary low-alloyed cop...
The hot deformation behavior of a Ti–5Al–5Mo–5V–3Cr alloy obtained by the Blended Elemental Powder Metallurgy approach was studied. Hot compression tests were performed to determine the stress–strain relationships at temperatures ranging from 800 °C to 1000 °C and strain rates between 0.1 and 20 s−1. Based on the collected data, a constitutive mode...
Groove rolling is one of the main process routes for the production of metal long products, such as bars, beams, wires, and rods. In this process, a workpiece is deformed by two or more rotating rolls to reduce the cross-section to achieve a desired cross-section shape. The shape is determined by the contour of the rolls’ surfaces, called the groov...
This study investigates the cold formability of twin-roll cast and rolled magnesium strips, specifically focusing on AZ31 and ZAX210 alloys. The aim is to assess the suitability of these alloys for various forming processes. The mechanical properties and formability characteristics of the strips were thoroughly examined to provide insights into the...
This study examines and models the three-dimensional anisotropic and asymmetric plastic behavior of hexagonal closed packed (HCP) metals, with focus on basal textured magnesium (Mg) alloys. Both experimental and numerical methods were employed. Uniaxial, pure shear, and equibiaxial tests were conducted, accompanied by in-situ strain field measureme...
High-strength low-alloy (HSLA) steels are low-carbon steels, making them an excellent construction material
for automotive applications, transportation of media such as oil and gas, or responsible marine structures often
operating in the harsh weather conditions of northern seas. These steels gain unique properties from microadditives of Nb, V or T...
New groove pass series for long products must be developed by backward engineering starting with the necessary mechanical properties and geometry of the final shape, with a highly iterative manual effort and with numerous manual decisions. Usually, established groove sequences are adopted in this process without consideration of material requiremen...
In sintering simulation, there are basically two approaches: microscale simulation, in which distinct particles or pores are regarded, and macroscale, where the porous body is regarded as continuum with variable density.Material parameters of the latter can be determined by experiment or by microscale models.Current microscale sintering models main...
The titanium matrix composite was produced through a hot compaction process at 1250 °C using the mixture of elemental powders with chemical composition of Ti-5Al-5Mo-5V-3Cr and 2 wt.% addition of boron carbide. The phase analysis via X-ray diffraction method was performed to confirm the occurrence of an in situ reaction between boron carbide and ti...
The effect of the novel controlled thermomechanical treatment, including torsion components in the elastic strain range during the isothermal holding on the microstructure and mechanical properties of the high-carbon nanobainitic steel, was investigated. TEM observations of the thermo-mechanically treated steel revealed bainitic ferrite laths with...
The processing maps developed by dynamic material modelling (DMM) method are now widely used in the design of hot forming processes. However, this applies to those processes that are relatively fast or are carried out under isothermal conditions, when it is possible to maintain the deformation parameters within the processing window. In the case of...
Due to increasing ecological and political pressure, manufacturers of long products tend to optimize their processes regarding energy consumption. A decisive factor for this optimization is the choice of groove shapes. Since the shape of the grooves alters the engine power demand, it’s also a significant factor to control the wear and service life...
Due to a combination of casting and rolling in one process step, twin-roll casting is an effective grain refinement method. This study compares the direct-chill cast (DC) state and the twin-roll cast (TRC) state of an AZ31 magnesium alloy in different steps regarding the microstructure, deformation behavior, and mechanical properties. In the initia...
This study compares AZ91 with AZ31 to investigate the influence of a higher Al content on the resulting microstructure, mechanical properties, and hot deformation behavior. While AZ31 exhibits a globular structure after casting, AZ91 shows a fully developed dendritic structure due to the promotion of dendrites. A heat treatment helped to homogenize...
The high strength Mg-4Zn-0.5Ca-0.5RE magnesium alloy was subjected to different hot deformation processes of extrusion, forging, and their combination for grain refinement and improvement of mechanical performance. A fine dynamically recrystallized (DRX) microstructure was obtained by the extrusion process accompanied with the fragmentation and dis...
Young's modulus for ferritic and austenitic steel at high temperatures is typically acquired through acoustic emission tests. In this study, we applied an inverse solution method to consider the effect of a temperature gradient on samples under experimental conditions. Wachman model, Varshni models, and power model were used to describe the influen...
In this study, the behavior of MnS particles in a steel matrix is investigated through in situ tensile testing and digital image correlation (DIC) analysis. The goal of this research is to understand the mechanical behavior of MnS inclusions based on their position in the steel matrix. To accomplish this, micro-dog bone-shaped samples are prepared,...
A process map is an intelligent way of visualizing material deformation behavior under hot working conditions by encompassing the activation and deactivation of different local mechanisms. Process maps are used by engineers to optimize temperature and strain rate conditions appropriate for the highly efficient hot workability of materials. Although...
This study aims to investigate the effect of chromium and molybdenum on the formation of pearlitic microstructure in 1% carbon steels. To obtain experimental data, 12mm wires of one benchmark (Fe-1C) and two trial alloys (Fe-1C-1.5Cr and Fe-1C 1.5Mo) are manufactured in-house by casting and hot caliber rolling. These wires are homogenized at a temp...
In the present work, the possibility of applying severe torsion deformation (STD) to a bulk near-equiatomic NiTi shape memory alloy in order to accumulate super-high strain and improve mechanical and functional properties was studied. STD was performed using the multidirectional test system “BÄHR MDS-830” at a temperature of 500 °C (the upper borde...
Multi-phase field modelling using MICRESS® has been used to perform simulations of the nucleation and evolution microstructure in a 2D domain as function of fundamental thermo-physical parameters, time, cooling rate and chemical composition during solidification. In order to have a better understanding of primary precipitates evolution during solid...
The present study aimed to investigate the effect of cold deformation on the precipitation kinetics of a binary CuSc alloy containing 0.4 wt.% scandium using the experimental analysis method of differential scanning calorimetry (DSC). Non-deformed and 75% cross-section-reduced cold-rolled supersaturated specimens were tested in non-isothermal DSC r...
The present study aimed to investigate the effect of cold deformation on the precipitation kinetics of a binary CuSc alloy containing 0.4 wt.% scandium using the experimental analysis method of differential scanning calorimetry (DSC). Non-deformed and 75% cross-section reduced cold-rolled, supersaturated specimens were tested at non-isothermal DSC...
For modelling of elastic work roll deformation in groove rolling, the finite element method offers a deep and detailed
modeling approach. Nevertheless, FEM calculations require a great amount of computational power and time. For
groove rolling, Schmidtchen et al. [1], [2] developed a pillar model derived from classic elementary theory to calculate...
The present study investigated the microstructural evolution of AA6082 aluminum alloy using ex-situ and in situ methods. Microstructural characterization was performed for the individual steps of the heat treatment parameters. To identify the morphology and kinetics of changes in precipitation and grain, the microstructure of the alloy was examined...
Copper alloys with chromium, hafnium, and scandium combining enhanced strength as well as high electrical and thermal conductivity are analyzed in depth. The aim is to compare the precipitation process during temperature exposure to meet increasing material requirements. This research focuses on alloying elements having a limited, maximum 1 wt.%, a...
The effect of a promising method of performing a thermomechanical treatment which provides the nanocrystalline structure formation in bulk NiTi shape memory alloy samples and a corresponding improvement to their properties was studied in the present work. The bi-axial severe plastic deformation of Ti-50.7at.%Ni alloy was carried out on the MaxStrai...
The hot deformation behavior of a Ti–5Al–5Mo–5V–3Cr alloy obtained by the Blended Elemental Powder Metallurgy approach was studied. Hot compression tests were performed to determine the stress–strain relationships at temperatures ranging from 800 °C to 1000 °C and strain rates between 0.1 and 20 s−1. Based on the collected data, a constitutive mode...
In this study, the effect of the energy release rate on the transformation-induced plasticity (TRIP) steel composite reinforced with 5 vol% ceramic particles is determined using the crystal plasticity simulation of the coupled brittle-ductile damage model and validated by experimental results. A miniature dog bone tensile sample is subjected to an...
In this work, two simulation models were used to investigate the local deformation and damage behavior of partially stabilized zirconia-reinforced metastable austenitic steel composites and validated by experimental results. An in situ quasi-static tensile test on a miniature dog bone sample is performed under an electron microscope up to 6.4% true...
In this study, we developed hot working process maps for incompressible TRIP steel composites with 0%, 5%, 10%, and 20% zirconia particles using crystal plasticity-based numerical simulations. Experimentally recorded material flow curves were used to calibrate material model parameters for TRIP steel and zirconia. The fitted material models were us...
Research activities considering lightweight design are dedicated to substituting classic mild steels by light metal alloys. Magnesium is especially promising due to its beneficial strength–density ratio, but its industrial use is still limited due to, e.g., unfavorable corrosion properties. Thus, a methodology for applying thin aluminum layers to m...
To understand the material flow and behavior during the production of shaped wires, different simulation approaches like the finite element method or the pillar theory [1] are available. In particular with regard to the calculation times, the latter one is suitable for optimization routines due to high accuracy and geometric flexibility at low comp...
For modelling of elastic work roll deformation in groove rolling, the finite element method offers a
deep and detailed modeling approach. Nevertheless, FEM calculations require a great amount of
computational power and time. For groove rolling, Schmidtchen et al. [1], [2] developed a pillar model
derived from classic elementary theory to calculate...
Finite element method simulations offer deep and detailed modeling of complex processes, but with high effort of computation power and time. The authors have developed a model based on the classic elementary theory of plasticity (slab method) which is able to describe inhomogeneous material behavior in flat rolling. The model divides the strip elem...
Finite element method simulations offer deep and detailed modeling of complex processes, but with high effort of computation power and time. The authors have developed a model based on the classic elementary theory of plasticity (slab method) which is able to describe inhomogeneous material behavior in flat rolling. The model divides the strip elem...