Martin F.-X. Wagner

• Univ.-Prof. Dr.-Ing. habil.
• Professor (Full) at Chemnitz University of Technology

Advanced pressing processes combine the short cycle times of conventional press hardening with the advantages of experimental quenching and partitioning steels. Their design typically involves complex thermal and mechanical load paths. In this study, a custom‐designed experimental heating/cooling setup is used to characterize a low‐alloy 37SiB6 ste...

During extrusion, the material is subjected to a heterogeneous deformation that results in the formation of gradients of microstructure and thus mechanical properties. In this study, using continuously cast commercially pure aluminum as a reference material, we show how a cast structure with coarse columnar grains affects the formation of these gra...

Equal-channel angular pressing (ECAP) allows for a rapid accumulation of massive amounts of plastic strain and thus promotes grain refinement. The deformation mode during ECAP is often simplified as simple shear, whereas experimental data and numerical simulations indicate the presence of a more complex deformation zone. As a consequence, the resul...

Quenching and partitioning (Q&P) heat treatments of low-alloy steels with exceptional property combinations are particularly promising. In this study, we characterize for the first time a new low-alloy steel to be processed using Q&P heat treatments. In combined experimental and numerical studies, we design a novel approach that effectively combine...

Limited availability of expensive alloying elements elevates low-alloyed steels to a unique position in the field of lightweight construction and mass production. Quenching and partitioning (Q&P) heat treatments of low-alloyed steels with exceptional property combinations are particularly promising. In this study, we characterize for the first time...

Severe plastic deformation (SPD) processes offer the possibility of improving the mechanical properties of metallic materials by grain refinement. However, this great potential has so far mostly been applied on a laboratory scale or on small series. Equal-Channel Angular Pressing (ECAP) also enables to integrate the advantages in industrial process...

At present, there are no experimental methods that allow for the complete direction-dependent mechanical characterization of tubes. This considerably limits the parameterization of complex, anisotropic material models. The present study introduces a new approach to overcome these limitations: tube sections are first flattened into a planar geometry...

In this study, we investigate the effect of severe plastic deformation by equal-channel angular pressing (ECAP) on the ordering kinetics and the microstructural evolution in an 18-carat AuCuAg alloy. Differential scanning calorimetry (DSC) measurements clearly show that the ordering process is significantly influenced by a fine-grained microstructu...

Bauschinger effects typically describe a reduction of yield strength after a load path change under uniaxial loading conditions. Here, we use in-plane loading to investigate, for the first time, Bauschinger effects in the sheet metal DC06 under well-defined equi-biaxial loading conditions: We first performed equi-biaxial tensile tests with crucifor...

Due to the inhomogeneous straining during processing, extrusion offers the potential to provide materials with graded properties for targeted applications. Cold extrusion of aluminum alloys typically results in a macrostructure with two characteristic regions: I. A fibrous core or center area with elongated grains that makes up the majority of the...

In this study, investigations into the deformation behavior of aluminum AA5083 at elevated temperatures were carried out on a newly developed test rig. The test rig was developed jointly with ZwickRoell GmbH & Co. KG (Germany) and is based on a Nakajima test carried out with heated dies. In this way, statements can be made about the lightweight pot...

Cold extrusion is an unconventional approach that can potentially combine the benefits of plastic shaping of metals and simultaneous strengthening by grain refinement and strain hardening. In this study, cast billets of the commercially pure AA1080 aluminum alloy were extruded at room temperature in a conventional extrusion press with various extru...

In this study, equal-channel angular pressing (ECAP)Equal Channel Angular Pressing (ECAP) was used to improve the mechanical propertiesMechanical propertiesof Aluminum AA7075Aluminum AA7075 sheet metal. Various approaches were tested for ECAPEqual Channel Angular Pressing (ECAP) route C, involving either channel geometry, forming temperature, or po...

In this study, we investigate the effect of different microstructures generated by severe plastic deformation on the thermal stability of an age-hardenable Al-Mg-Si alloy (AA6082). To analyze recovery and recrystallization we investigate the internal friction at various excitation frequencies and the microstructural evolution of the material in a w...

Equal-channel angular pressing (ECAP) is an established method for the improvement of mechanical properties by grain refinement through shear strains. While there is a profound knowledge about ECAP of bulk materials, there is only a little information on the effect of ECAP on sheet metals. Therefore, a tool was developed that is able to perform ECA...

We investigate the evolution of shear bands in a Ti-10V-3Fe-2Al alloy with three different initial microstructures: solution-annealed β-titanium, β-titanium with primary α-phase precipitates as well as a condition with primary and secondary α-phase precipitates. Quasi-static and dynamic testing of compression-shear specimens with strain rates of 10...

A new approach for equal‐channel angular pressing (ECAP) of thin AA5083 sheets using two different orientations is investigated to address the issues of sheet metal ECAP. The method includes the deformation of a stack of 6 individual sheets supported by bulk material pieces placed on both sides of the stack. An excess length of the support material...

In der Automobilindustrie ist die Anwendung von monolithischen Profilstrukturen etabliert. Jedoch bietet der Einsatz von Hybridprofilen, die aus einem faserverstärkten Polymer (FVK) und einer duktilen Metalllegierung bestehen, eine im Vergleich vorteilhafte Kombination aus mechanischen Eigenschaften und resultierendem Bauteilgewicht. Um eine effizi...

Tube hydroforming is a well-established process in industry for producing complex shaped parts with closed cross section geometry and high geometrical accuracy. Hot-metal gas forming (HMGF) extends the conventional tube hydroforming process by a complex thermo-mechanical approach and thus potentially enables the complex processing of tubes from the...

Collision welding is a high-speed joining technology based on the plastic deformation of at least one of the joining partners. During the process, several phenomena like the formation of a so-called jet and a cloud of particles occur and enable bond formation. However, the interaction of these phenomena and how they are influenced by the amount of...

Collision welding processes are accompanied by the ejection of a metal jet, a cloud of particles (CoP), or both phenomena, respectively. The purpose of this study is to investigate the formation, the characteristics as well as the influence of the CoP on weld formation. Impact welding experiments on three different setups in normal ambient atmosphe...

Adiabatic blanking of advanced high-strength steels with initial flow stresses above 1300 MPa is investigated. The blanked edge exhibits a unique S-shape. Localisation and properties of shear bands are analysed in shear-compression tests. A shear-compression stress state before separation leads to blanked edges without fracture zone, burr, or roll-...

Compared to monolithic constructions, hybrid structures have properties that are more beneficial. For example, parts, which are made of a combination of a fiber rein-forced polymer (FRP) and a ductile metal, can bear high operation loads on the one hand. On the other hand, the resulting parts show high energy dissipation rates within crashes. Never...

Equal-channel angular pressing (ECAP) allows to rapidly accumulate massive amounts of plastic strain and thus to promote grain refinement in metals, which is one of the main goals of severe plastic deformation methods. While early models have simplified the deformation during ECAP as simple shear, experimental observations and numerical simulations...

This work proposes a manufacturing chain that combines the two key technologies Incremental Swivel Bending (ISB) and Quenching and Partitioning (Q-P). While incremental forming methods offer chances for production flexibility, strain hardening often exhausts material’s ductility. Heat treatment processes can potentially renew the material’s capabil...

The quenching and partitioning (Q&P) heat treatment enables a higher formability of high strength martensitic steels. Therefore it is necessary to have some metastable austenite in the microstructure, which transforms in martensite during plastic deformation (transformation induced plasticity - TRIP effect). This microstructure can be achieved by t...

Achieving superplasticity requires a homogeneous, fine-grained microstructure with (primarily) globular grains. Equal-Channel Angular Pressing (ECAP) is an established method that produces considerable grain refinement. While there is substantial knowledge about work hardening and grain refinement during ECAP of bulk materials, there is only little...

This paper addresses localized plastic flow during equal-channel angular pressing (ECAP) of an AA6060 aluminum alloy. We observe an alternating formation of shear bands and matrix bands during ECAP that leads to pronounced strain partitioning without cracking. Local deformation is analyzed by considering the distortion of indents along flow lines i...

We investigate an extraordinarily high ductility in a low alloy carbon steel at an elevated temperature after a quenching and partitioning (Q&P) treatment. The conventional (quenched and tempered) reference material does not show similar behavior. Interestingly, the Q&P treated material’s ductility is considerably reduced at increasing strain rates...

The mechanical behavior of pseudoelastic NiTi is strongly affected by the properties of its twinned martensitic microstructures, which has been recently demonstrated by observations of an anisotropic material response during nanoindentation. In this paper, we apply the phenomenological theory of martensitic transformations to the multi-axial load c...

The microstructure of aluminum‐steel compounds fabricated by magnetic pulse welding are investigated. Electron backscatter diffraction, energy dispersive x‐ray spectroscopy and scanning electron microscopy revealed the existence of several different phases along the weld seam. While one layer could be identified as aluminum solid solution, a very t...

We report on recurrent shear localization by formation of strictly alternating shear and matrix bands during equal-channel angular pressing (ECAP) of a 6000 series aluminum alloy. The strain partitioning process is documented by analyzing the deformation of a grid of indents as well as reconstructing the corresponding flow lines. Interestingly, she...

After reporting on the ability of micro-EDM to significantly alter the transformation behaviour of Nitinol whereby increasing discharge energy reduces thermal hysteresis and results in a three-peak reverse phase transformation on heating, this study helps to further characterize the Nitinol micro-EDM process. This is by closely varying discharge en...

In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P...

This paper examines how the initial austenite grain size in quench and partitioning (Q-P) processes influences the final mechanical properties of Q-P steels. Differences in austenite grain size distribution may result, for example, from uneven heating rates of semi-finished products prior to a forging process. In order to quantify this influence, a...

Hammer-peening can replace extensive hand-polishing during the processing of freeform surfaces, but it is rarely applied in practice due to the interplay of numerous parameters, including the process and tool parameters as well as the geometry and the material of the workpiece. In the present study we systematically investigate the effect of tool r...

Deformation at high strain rates in combination with local thermal softening can lead to the formation of so-called adiabatic shear bands. These shear bands occur when the macroscopic deformation is concentrated in microscopic areas. The fundamental thermomechanical processes and micromechanical mechanisms acting during adiabatic shear band formati...

The fatigue crack propagation (FCP) behavior of a quenched and partitioned (Q&P), low-alloyed CSiCrMn steel containing 12% of retained austenite is investigated in ΔK-controlled tests at different R-ratios and compared with its quenched and tempered (QT) counterpart, containing 4% of retained austenite. Characteristic features of the crack wake and...

Equal-channel angular pressing (ECAP) is often used as effective tool for grain refinement for many different metallic materials. It is well known that grain size is an important microstructural feature influencing superplastic properties of fcc materials like aluminum alloys. The magnitude of introduced shear strain depends on geometrical paramete...

Quenching and partitioning (Q&P) steels show a good balance between strength and ductility due to a special heat treatment that allows to adjust a microstructure of martensite with a fraction of stabilized retained austenite. The final heat treatment step is performed at low temperatures. Therefore, joining of Q&P steels is a big challenge. On the...

An experimental steel 42SiCr was heat treated with a quenching and partitioning treatment in order to achieve high strength and at the same time acceptable ductility. This crucial combination requires the formation of a martensitic microstructure with a small volume fraction of retained austenite embedded on a microscopic scale. The objective of th...

Funktionale Hybridtextilien mit passiven und aktiven Metall-Monofilamenten

Quenching and partitioning (Q&P) treatments result in promising mechanical properties of advanced high-strength steels. However, recent studies indicate that Q&P steels are very susceptible to hydrogen embrittlement (HE). Using slow strain-rate tests, the effects of hydrogen charging in different media without and with recombination poison were inv...

In many metallic materials, load path changes result in Bauschinger effects, i.e., a reduction of yield strength. In this study, we present results of a microstructural investigation on Bauschinger effects in the sheet metal DC06 subjected to in-plane uniaxial loading. We performed tension-compression tests with different values of maximum tensile...

Pseudoelastic NiTi shape memory alloys exhibit different stress–strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to systematically analyze how characteristic features...

Pseudoelastic NiTi shape memory alloys exhibit different stress-strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to systematically analyze how characteristic features...

The interfaces between layered materials play an important role for the overall mechanical behavior of hybrid composites, particularly during dynamic loading. Moreover, in complex-shaped composites, interfacial failure is strongly affected by the geometry and size of these contact interfaces. As preliminary work for the design of a novel sample geo...

Among the advanced high-strength steels, quenching and partitioning (Q&P) steels provide excellent ultimate tensile strength in combination with good ductility. The mass fraction of martensite and austenite can be tailored by the Q&P treatment. In this study, the impact of the microstructure on the corrosion behaviour is investigated. For this, the...

Academia and industry alike are faced with an ever-growing demand for energy-efficiency and reduced mass [...]

The aim is to realize a Q&P (Quenching and Partitioning) process for a hot forged component made of low-alloyed advanced high-strength steel (AHSS) 42MnSiCr. One advantage of this steel is the low alloy concept which is cost-effective. After forging, the component is cooled down to room temperature with a subsequent heat treatment to achieve the ch...

We studied the microstructural evolution of the low stacking fault energy $\alpha$-brass alloy CuZn15 during accumulative roll bonding (ARB). Most notably, the typical brass-type texture was clearly observed after four ARB passes (approx. 93.8 % total thickness reduction), before significant shear localization set in. This observation contradicts t...

We studied the microstructural evolution of the low stacking fault energy $\alpha$-brass alloy CuZn15 during accumulative roll bonding (ARB). Most notably, the typical brass-type texture was clearly observed after four ARB passes (approx. 93.8 % total thickness reduction), before significant shear localization set in. This observation contradicts t...

The aim is to realize a Q&P (Quenching and Partitioning) process for a hot forged component made of low-alloyed advanced high-strength steel (AHSS) 42MnSiCr. One advantage of this steel is the low alloy concept which is cost-effective. After forging, the component is cooled down to room temperature with a subsequent heat treatment to achieve the ch...

According to the concept of an intrinsic hybrid composite, adhesive bonding is designed for generating the connection between the applied fiber reinforced polymer and a metallic insert. To induce adhesive bonding, a metallic insert, made of aluminum, is coated. This contribution focusses on the development of a suitable coating system. To this end,...

This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the joining of the cam onto the shaft. When manufactured, the connection is test...

This paper presents an innovative methodology for integrated technical-economic evaluations of extrusion technologies and aims to show potentials of severe plastic deformation (SPD) technologies. Extrusion technologies and processes such as SPD have a strong influence on properties of aluminium-based lightweight materials. Hence, research and devel...

In this contribution, we study the microstructural evolution of an age-hardenable AA6082 aluminum alloy during severe plastic deformation by gradation extrusion. A novel die design allowing an interruption of processing and nondestructive billet removal was developed. A systematic study on the microstructure gradient at different points of a single...

The Portevin–Le Châtelier (PLC) effect often results in serrated plastic flow during tensile testing of aluminum alloys. Its magnitude and characteristics are often sensitive to a material’s heat treatment condition and to the applied strain rate and deformation temperature. In this study, we analyze the plastic deformation behavior of an age-harde...

Severe plastic deformation (SPD) can be used to generate ultra-fine grained microstructures and thus to increase the strength of many materials. Unfortunately, high strength aluminum alloys are generally hard to deform, which puts severe limits on the feasibility of conventional SPD methods. In this study, we use low temperature equal-channel angul...

Equal-Channel Angular Pressing (ECAP) is a method used to introduce severe plastic deformation into a metallic billet without changing its geometry. In special cases, strain localization occurs and a pattern consisting of regions with high and low deformation (so-called shear and matrix bands) can emerge. This paper studies this phenomenon numerica...

Processing of AA6060 aluminum alloys for semi-products usually includes hot extrusion with subsequent artificial aging for several hours. Processing below the recrystallization temperature allows for an increased strength at a significantly reduced annealing time by combining strain hardening and precipitation hardening. In this study, we investiga...

Due to a combination of different classes of materials, intrinsic hybrid composites are characterised by high strength and low weight. The mechanical properties of hybrid parts are mainly determined by the interface between the different materials. Consequently, this interface has to be considered in detail within the development of an intrinsic hy...

Biaxial tensile testing of sheet metals is becoming increasingly popular for sheet metal forming. Determining equivalent stresses in biaxial tensile specimens is more complicated than in conventional uniaxial tensile specimens. In the present study, we compare four different approaches to calculate effective stresses during biaxial tensile loading...

Equal-Channel Angular Pressing (ECAP) is a method used to introduce severe plastic deformation into a metallic billet without changing its geometry. In special cases strain localization occurs and a pattern consisting of regions with high and low deformation (so-called shear and matrix bands) can emerge. This paper studies this phenomenon numerical...

Severe plastic deformation techniques can produce ultrafine-grained aluminum alloys with high strength and ductility, but further processing often requires costly and/ or time-consuming cutting or forming processes. In this study, we investigate the potential of an alternative processing route that operates below recrystallization temperature and t...

Many crystalline materials exhibit twinned microstructures, where well-defined orientation relationships define the special symmetry between different, elastically anisotropic twin variants. When such twins are subjected to external loading, additional internal stresses necessarily occur at the twin boundaries in order to maintain compatibility. Th...

Understanding the deformation behavior of multi-phase alloys under external loading requires careful mechanical characterization of the individual constituent phases at various length scales. The present study first evaluates the elastic moduli and hardness of the microstructural constituents viz. primary α (αp) and transformed β (secondary α (αs)...

Recent work shows that severe plastic deformation processes such as ECAP or HPT considerably accelerate the precipitation kinetics of Al-Cu alloys. In this study, the authors analyze how a combination of mechanical load, aging time (and increased plastic strain), and aging temperature affects the precipitation kinetics of an AA2017 alloy after ECAP...

In automotive industry advanced high strength steels (AHSS) are widely used. However, the modeling of such material behavior is challenging. The demand to shear-cut AHSS parts without additional post-processing steps like deburring or heat-treatment manufacturing of high quality cutting surface is impossible. High strain rate and local temperature...

Pseudoelastic NiTi shape memory alloys (SMAs) exhibit a distinct mode of localized deformation/ stress induced martensitic transformation (SIMT) via formation and propagation of martensite bands under uniaxial tension. In contrast, the deformation appears to proceed homogeneously under simple compression. Moreover, confirmed by recent experiments,...

The shape memory community’s conventional wisdom holds that localized deformation (transformation via the formation and growth of martensite bands) only occurs under tension, whereas compressive loading is supposed to result in homogeneous deformation. In this contribution, we present experimental results on shear-compression testing using a specia...

Compared to conventional extrusion processes, extrusion below recrystallization temperature leads to considerably accelerated precipitation kinetics (including a technologically attractive reduction of aging time)and higher hardness, which offers a high potential for the integration in industrial process chains. Due to the inhomogeneous straining d...

In most engineering applications, materials are subjected to complex load cases rather than the simple uniaxial ones typically used for material characterization. To experimentally study the material behavior under a combination of compression and shear, an inclined compression specimen can be used. This specimen has been applied in various earlier...

Severe plastic deformation methods are commonly used to increase the strength of materials by generating ultrafine-grained microstructures. The application of these methods to Al-Cu alloys is, however, difficult because of their poor formability at room temperature. An additional reduction of formability of such alloys occurs when ceramic particles...

Both in research and in the light of industrial applications, there is a growing interest in methods to characterize the mechanical behavior of materials at high strain rates. This is particularly true for steels (the most important structural materials), where often the strain rate-dependent material behavior also needs to be characterized in a wi...

Classically, the Bauschinger effect refers to a reduction of yield strength after a load path change. In this contribution, we present results of an experimental and microstructural investigation on Bauschinger effects in an AA1050 sheet metal (with 1 mm thickness) subjected to in-plane uniaxial loading. We performed tension-compression tests with...

In the automotive industry, advanced high strength steels (AHSS) are widely used as sheet part components to reduce weight, even though this leads to several challenges. The demand for high-quality shear cutting surfaces that do not require reworking can be fulfilled by adiabatic shear cutting: High strain rates and local temperatures lead to the f...

The deformation behavior of pseudoelastic NiTi shape memory alloys (SMAs) has been extensively characterized under uniaxial tensile loading. Previous studies have shown that NiTi SMAs exhibit a distinct mode of localized deformation (nucleation and propagation of well-defined martensite bands) under uniaxial tension that leads to a constant stress...

Reducing friction plays a key role in the technological application of severe plastic deformation (SPD) techniques like equal-channel angular pressing (ECAP). In this paper, we report on an experimental study that investigates the suitability of various commercially available lubricants for SPD processing. We consider a custom-built friction test t...

Epitaxial films have the potential to be used as model systems for fundamental investigations on the martensitic transformation in binary NiTi. In this paper, we discuss growth of binary NiTi thin films on single crystalline MgO substrates. Sputter deposition is used to grow NiTi films. Films prepared by complementary preparation routes (with diffe...

Epitaxial films have the potential to be used as model systems for fundamental investigations on the martensitic transformation in binary NiTi. In this paper, we discuss growth of binary NiTi thin films on single crystalline MgO substrates. Sputter deposition is used to grow NiTi films. Films prepared by complementary preparation routes (with diffe...

We present experimental results on the deposition of Nickel Titanium (NiTi) films on graphene substrates using a PVD magnetron sputter process. Characterization of the 2–4 micron thick NiTi films by electron microscopy, electron backscatter diffraction, and transmission electron microscopy shows that grain size and orientation of the thin NiTi film...

This paper describes selected capabilities of unconventional processing of steels in semi-solid state under various process conditions and with the use of various steel chemistries for obtaining unusual structures formed by rapid solidification in combination with other procedures. This investigation involves the use of severe plastic deformation t...

Magnetocaloric materials are promising as solid state refrigerants for more efficient and environmentally friendly cooling devices. The highest effects have been observed in materials that exhibit a first-order phase transition. These transformations proceed by nucleation and growth which lead to a hysteresis. Such irreversible processes are undesi...

Most investigations on NiTi-based shape memory alloys involve large-scale bulk material; knowledge about the martensitic transformation in small-scale NiTi structures is still limited. In this paper, we study the microstructures of thin NiTi layers and their mechanical properties, and we discuss typical challenges that arise when experiments are pe...

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mech...