Karl Ulrich Kainer

Helmholtz-Zentrum Hereon | HZG · Magnesium Innovations Centre (MagIC)

Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability, which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries. However, their practical applications are still limited because of th...

This paper investigates the influence of addition of Ca in a Y-Zn-containing magnesium alloy on the dynamic and static recrystallization behaviors and reveals the formation mechanism of the quadrupole texture during thermomechanical processing. Direct extrusion of flat bands has been conducted at various process conditions to study the difference b...

Mg–Gd alloys are candidates for degradable implants combining favorable mechanical and corrosion properties. Gd has a high solid solubility in Mg and an acceptable biocompatibility. The influences of different amount of Gd additions and solid solution (T4) treatment on mechanical properties and corrosion in 0.9 wt% NaCl and cell culture medium (CCM...

The application of magnesium flat products is affected by the limited formability at room temperature and the anisotropy of the mechanical properties. The main reason for this is the underlying hexagonal crystal structure of magnesium and the development of strong crystallographic textures during massive forming processes with distinct alignment of...

Mg–1Al, Mg–0.9Y, Mg–2Gd, Mg–1.5Zn, and Mg–0.5Ca binary alloys were chosen to clarify the hot tearing mechanism since they exhibited the highest hot tearing susceptibility (HTS) among each binary alloy systems. Hot tearing tests of these five binary magnesium alloys were carried out by a constrained rod-casting apparatus. 3D X-ray tomography technol...

The existence of iron impurity in magnesium (Mg) is conventionally deemed detrimental to the corrosion resistance against the inorganic solutions, especially over its tolerance limit. We deliberately investigated the biodegradation properties of pure Mg with different contents of Fe by immersing in DMEM+10% FBS. Surprisingly, the impurity of Fe, ev...

In the present study, the influence of Zn or Al addition as a third alloying element on the deformation mechanisms of Mg–Nd-based alloys was investigated by quasi in situ tensile tests. Distinct mechanical behaviors were observed between Mg–1.0 Zn–1.7 Nd (ZN12, in wt.%) and Mg–1.0 Al–1.7 Nd (AN12) alloys. The ZN12 alloy showed a lower yield strengt...

Previous investigations demonstrated that rare‐earth elements (REs) could improve their creep properties effectively. Herein, the influence of Y content on the creep properties of magnesium is investigated systematically with different amount of Y additions. The mechanisms responsible for creep deformation are clarified by the analysis of stress ex...

Texture modification during sheet rolling appears differently in binary Mg-RE (rare-earth) or MgCa alloy, compared to their ternary counterparts containing Zn. The differences in texture development and the active deformation mechanisms under tensile loading were investigated in the binary alloys. These analyses are based on in-situ synchrotron exp...

This collection from the 12th International Conference on Magnesium Alloys and Their Applications (Mg 2021)—the longest running conference dedicated to the development of magnesium alloys—covers the breadth of magnesium research and development, from primary production to applications to end-of-life management. Authors from academia, government, an...

The influence of amount of intermetallics on the degradation of as-extruded Mg-Nd alloys with different contents of Nd was investigated via immersion testing in DMEM+10% FBS under cell culture conditions and subsequent microstructural characterizations. It is found that the presence of intermetallic particles Mg41Nd5 affects the corrosion of Mg-Nd...

Wires of magnesium alloys possess a high potential, e.g., as filler materials, for joining applications but also for biodegradable applications, such as suture materials. While the typical process of producing wires is based on a wire drawing process, direct extrusion by using adjusted dies to deal with high degrees of deformation allows a one-step...

The influence of intermetallic microstructure on the degradation of Mg-5Nd alloy with different heat treatments was investigated via immersion testing in DMEM + 10 pct FBS under cell culture conditions and subsequent microstructural characterizations. It was found that T4 heat-treated sample had the poorest corrosion resistance due to the lack of f...

In previously published research, creep resistance of commercial alloy Elektron21 (El21) and El21 + 1% AlN/Al nanocomposite were predominantly investigated in as-cast condition, little work focused on creep resistance following heat treatment. In this work, El21 and its nanocomposite with and without T6 treatment (520 °C for 8 h and 200 °C for 16 h...

In 0.5 wt.% NaCl aqueous solution, Mg-10Gd alloy shows promising corrosion resistance. The microstructure of this alloy was modified via heat treatments to understand the effect of accompanying microstructural changes on the corrosion resistance. It was found that corrosion performance depends both on the amount and the distribution of the cathodic...

The creep properties of Mg-2.85Nd-0.92Gd-0.41Zr-0.29Zn (El21) alloys with additions of 0.25 wt% Al, 0.75 wt% AlN and 1 wt% AlN/Al nanoparticles (NPs) were studied over a stress range from 80 to 140 MPa at 240 °C, respectively. The individual/synergistic roles of Al and AlN in the El21 alloy were investigated systematically to reveal their creep str...

Three magnesium alloys with texture and microstructure modifying elements, binary M2, and the alloyed counterparts with Ca (MX21) and rare earth element (ME21) were extruded to flat bands under similar conditions. The microstructure and texture in extrusion significantly differ from those developed in rolled magnesium sheets. The influence on the m...

AZ91D and MRI153M alloys were produced by thixomolding. Their corrosion resistance is significantly higher than that of similar materials produced by ingot or die‐casting. A corrosion rate smaller than 0.2 mm/year in 5 wt% NaCl solution is measured for the thixomolded AZ91D alloy. The corrosion behaviour was evaluated using immersion tests, electro...

Open-porous MAX phase skeletons from Ti3SiC2 were manufactured by Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) and subsequently subjected to squeeze casting infiltration with an Al-Si lightweight casting alloy (EN AC-44200). This alloy was chosen due to its high flowability, corrosion resistance and good machinability. The...

The development of microstructure and texture during flat product extrusion of magnesium alloys differs significantly from those of rolled sheets. It has especially been shown that the range of microstructures and textures is broad in the case of extrusion which allows significant variations of the resulting textures. Three wrought magnesium-zinc a...

An advanced mathematical approach to describe the influence of corrosion products on the corrosion rate is presented here. The related model can be used as input equation for numerical predictive corrosion simulations or simply as an empirical model, to extrapolate experimental data of corrosion tests to longer times and to interpret the physical p...

The influence of Nd contents and particles on the microstructure and mechanical properties of extruded Mg alloys are discussed. Pure Mg and binary Mg-xNd (x = 0.2 wt.%, 0.5 wt.%, 1 wt.%, 2 wt.%, 5 wt.%) alloys were cast and extruded. Hardness and tensile/compression tests were measured on those alloys. The results show that the addition of Nd to Mg...

Corrigendum to “Influence of Nd or Ca addition on the dislocation activity and texture changes of Mg–Zn alloy sheets under uniaxial tensile loading” [Mater. Sci. Eng.: A 761 (22 July 2019) 138053]

Effects of 0.25% Al addition and the high shearing dispersion technique (HSDT) on the microstructure and creep resistance of Mg-2.85Nd-0.92Gd-0.41Zr-0.29Zn (Elektron21, El21) alloy were investigated. Compressive creep testes were performed at 240 °C over a stress range between 80 and 140 MPa. The results indicate that the creep resistance of El21 w...

The microstructure and texture evolution during static recrystallization of Mg-Nd alloys were investigated. Depending on the third alloying element added into Mg-Nd alloy, either Al or Zn, diverse textures are formed during recrystallization annealing. The rolled Mg-2Nd-1Zn sheet shows a high activity of prismatic slip and the formation of a weak t...

In situ hard X-ray diffraction experiments were carried out to investigate the dislocation slip activity of Mg-1 wt.% Zn-based alloys containing Nd or Ca during tensile loading. Diffraction patterns collected during tensile loading at 3 temperatures were analyzed using a convolutional multiple whole profile fitting procedure. High activation of non...

A homogeneous microstructure of as-cast magnesium alloys is desired to improve the formability during their subsequent thermomechanical processing. Owing to its similar crystal structure to Mg, the part of Zr formed by peritectic reaction during solidification was considered to be the most effective nucleants for alpha-Mg. However, regarding the Al...

Elektron21 (E21) and its composites with additions of 0.25 wt.%, 0.5 wt.%, and 1 wt.% AlN/Al nanoparticles (NPs) were fabricated by a high shear dispersion technology. Their creep properties were investigated over a stress range between 80 MPa and 140 MPa at 240°C. The grain size exhibits an obvious increase with the addition of AlN/Al NPs compared...

The precipitation behavior of Mg-Al alloys during isothermal ageing has been investigated by dilatometry. Only continuous precipitation was observed in Mg-5.5Al during ageing at 175°C, 200°C, or 225°C, while both discontinuous and continuous precipitation occurred in Mg-8.9Al at the same ageing temperatures. Dilatometry curves showed that Mg-8.9Al...

The effect of second phases on the creep behavior of Mg-Ca-Zr alloys was investigated. Casting and hot-extrusion processes were performed to prepare Mg-xCa-0.5Zr (x = 0 wt.%, 0.3 wt.% and 0.6 wt.%) alloys with different morphologies and distributions of second phases. The as-cast microstructures of Mg-Ca-Zr alloys consisted of an Mg matrix and coar...

A high shearing dispersion technique (HSDT) was utilized for the first time to incorporate AlN/Al nanoparticles in Mg-2.85Nd-0.92Gd-0.41Zr-0.29Zn (Elektron21) alloy. Compressive creep tests of unreinforced and reinforced Elektron21 alloys were performed at 240 °C with an applied stress of between 70-140 MPa. The results show that HSDT is an effecti...

Relative contribution of individual strengthening mechanisms to the yield strength of Mg–0–15 wt% Gd alloys were investigated. Alloys with different grain size were prepared by adding Zr and hot extrusion. Hardness and tensile/compression yield strength were tested on the alloys after solid solution treatment and extrusion. Hall-Petch constants wer...

A homogeneous microstructure of as-cast magnesium alloys is desired to improve the formability during their subsequent thermomechanical processing. Owing to its similar crystal structure to Mg, the part of Zr formed by peritectic reaction during solidification was considered to be the most effective nucleant for alpha-Mg. However, regarding the Al-...

Magnesium alloys with rare earth or Ca additions often form weak textures during rolling of magnesium sheets or extrusion of round bars. However, in the case of the extrusion of flat profiles of such alloys strong textures may develop. This is of fundamental importance because weaker textures are associated with higher ductility or formability. Var...

The influence of SiO2 particles on the microstructure, phase composition, corrosion and wear performance of plasma electrolytic oxidation (PEO) coatings on AM50 Mg was investigated. Different treatment durations were applied to fabricate coatings in an alkaline, phosphate-based electrolyte (1 g/L KOH + 20 g/L Na3PO4 + 5 g/L SiO2), aiming to control...

The influence of particles with different melting points on the microstructure, phase composition and properties of plasma electrolytic oxidation (PEO) coatings was investigated. PEO coatings were produced on AM50 Mg alloy from an alkaline phosphate-based electrolyte (1 g/L KOH + 20 g/L Na3PO4) with and without addition of clay, SiO2, Si3Ni4 and Si...

Elektron21-based alloy reinforced with 0.5 wt% AlN nanoparticles was fabricated using the intensive melt shearing technique. The influence of intensive shear technique and nanoparticles on the microstructure, mechanical properties at room temperature and creep properties at 513K were investigated systematically. The results show that intensive melt...

Mg-RE alloys were designed as biodegradable implant materials which show a good combination of mechanical and degradation properties. Ag was reported to improve the ductility and its ion can prevent bacterial infections. The addition of alloying element Ca contributes to the solid solution and precipitate strengthening. In this work, the microstruc...

The influences of Nd content on microstructures, mechanical properties and tension-compressing yield asymmetry at room temperature were investigated on extruded pure Mg and Mg-Nd binary alloys. Nd in the range of 0.05-0.63 at.% has been added to pure Mg. The grain sizes of the Mg-Nd alloys decreased with increasing Nd content. In particular, the gr...

The texture weakening is an effective way to improve the mechanical properties and the formability of wrought Mg alloys. The addition of rare earth elements (RE) into Mg alloys leads to a texture weakening during thermomechanical processes with a less distinct alignment of basal planes parallel to the main deformation axis. Understanding the role o...

The texture weakening is an effective way to improve the mechanical properties and the formability of wrought Mg alloys. The addition of rare earth elements (RE) into Mg alloys leads to a texture weakening during thermomechanical processes with a less distinct alignment of basal planes parallel to the main deformation axis. Understanding the role o...

The Young's modulus for a series of binary Mg–Gd and Mg–Nd alloys are studied in the present work. Fine and homogeneous grain structures are prepared by using hot extrusion. The results demonstrate that the Young's modulus of Mg–Gd alloys increase linearly by the increase of Gd in solid solution. Aging treatments are applied to the Mg–0.79–2.43 at%...

Plasma electrolytic oxidation (PEO) technology is widely used for coating of light metals and their alloys because of the excellent coating properties it provides and its non-line-of-sight treatment which allows forming coatings on substrates with complex geometry. However, non-uniform coating thickness and surface properties may be an issue at dif...

An advanced computational model based on the mixed potential theory (MPT) is presented, which is able to predict the progress of uniform as well as galvanic corrosion on car components made of zinc and steel (CR300). Previous approaches based on the MPT are computationally less challenging than other simulation models and are typically suitable for...

As-cast ZK40 alloys, modified with the addition of CaO, Gd, Nd and Y were investigated. Solution heat treatments were performed based on differential thermal analysis results. The unmodified ZK40 alloy exhibited microstructure with nearly no intermetallic compound but with precipitates formed during the solution treatment. The modified ZK40 alloys...

Plasma electrolytic oxidation (PEO) is a well-known surface treatment for Mg alloys, while high porosity is an issue to achieve long-term corrosion protection. Nevertheless, the presence of inherent porosity can be turned into advantage while used as nano/micro-structured reservoir of corrosion inhibitors or functional agents next to Mg surface pro...

Mg alloys attract more and more attentions for biomedical applications. Mg-Gd alloys were designed as biodegradable implant materials which combine favorable mechanical and corrosion properties. In this work, the microstructure and mechanical properties of binary Mg-2Gd, ternary Mg-2Gd-(Ag, Ca) and quaternary Mg-2Gd-2Ag-0.4Ca alloys were investigat...

The microstructures of as-cast ZK40, ZK40 with 2% (mass fraction) CaO and ZK40 with 1% (mass fraction) Y were investigated, and the intermetallic phase morphology and the distribution were characterised. By having discrete intermetallic particles at the grain boundaries for the ZK40, the microstructure was modified to a semi-continuous network of i...

As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of such sheets is complex, and therefore expensive, and requi...

The microstructure and mechanical properties of as-cast Mg-Ca-Y-Zr alloys with different Y contents were investigated. The alloy containing 0.5 wt.% Y exhibited finer grains compared to the alloys with higher Y content. All alloys had a dendritic microstructure with eutectics composed of α-Mg and Ca-rich intermetallic phases. Few Mg-Y-rich intermet...

Among all alloying elements the rare earth elements (RE) play a key role in improving the ductility, high temperature strength and corrosion resistance effectively for magnesium and its alloys. The present work investigated the influences of single alloying or multi heavy REs (Gd, Dy and Y) alloying on the strengthening and ductilizing of magnesium...

Magnesium has been studied as a potential hydrogen storage material for several decades because of its relatively high hydrogen storage capacity, fast sorption kinetics (when doped with transition metal based additives), and abundance. This research aims to study the possibility to use waste magnesium alloys to produce good quality MgH2. The produc...

A significant number of studies have been dedicated to the fabrication and properties of metallic foams. The most recent research is focused on metals with low weight and good mechanical properties, such as titanium, aluminum, and magnesium. Whereas the first two are already fairly well studied and already find application in industry, magnesium cu...

Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys. In this contribution, recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design, focusing on Mg-Al, Mg-Zn...

Plasma electrolytic oxidation (PEO) process is employed to coat AM50 magnesium alloy in an alkaline phosphate solution applying constant voltage. Effects of treatment time on the morphology, composition and thickness of the resulting coatings are investigated by XRD and SEM respectively. Based on the analysis of the experimental results, a mathemat...

In this work, a combination of in situ experiments; synchrotron diffraction and synchrotron tomography were used to study the solidification behaviour of Mg-5Nd-5Zn (wt. %). The samples were cooled with a cooling rate of 100 °C/min and 5 °C/min in the in situ synchrotron diffraction experiment and in situ synchrotron tomography experiments respecti...

Rare earth element Dy is one of the promising alloying elements for magnesium alloy as biodegradable implants. To understand the effect of Dy in solid solution on the degradation of Mg-Dy alloys in simulated physiological conditions, the present work studied the microstructure and degradation behavior of Mg-Dy alloys in cell culture medium. It is f...

The undermining of organic coatings on galvanized steel sheets is being characterized using transient finite element simulations. Galvanized steel sheets are the most widespread parts in the automobile industry. Thus, the delamination beginning from coating defects is a crucial issue to deal with. This matter is depicted through a manually brought...

The properties of commercially viable Mg alloys are not sufficient for many of the envisaged applications. The combination of Zn and rare earth metals is one of the most effective ways to enhance the mechanical properties of Mg alloys. In situ synchrotron radiation diffraction is a unique method to investigate the dynamic microstructural processes...

In order to investigate the influence of solute atoms and particles on Young’s modulus of magnesium, series of binary Mg–Gd and Mg–Nd alloys were prepared using hot extrusion. With increasing Gd content from 0 to 2.654 at.% Young’s modulus of Mg–Gd alloys increases linearly from 44.0 to 45.3 GPa. Regarding Mg–Nd alloys, Young’s modulus firstly decr...

Process optimization is one pathway to maximizing strength of a given alloy. Thixomolding® is a semi-solid casting process that combines pores reduction with a typical bimodal grain size distribution that can lead to enhanced strength. AZ91D and AZX911 were processed via Thixomolding® using two different processing conditions to change fraction sol...

In situ synchrotron tomography is a unique technique to study 3D microstructure evolution during solidification due to the high brilliance of the beam and the short acquisition time of the detector systems. In this work, in situ synchrotron tomographic observations were performed during the solidification of Mg–5Nd–5Zn (wt%) alloy with a cooling ra...

The effects of Mn (peritectic system) and Zn (eutectic system) on the grain refinement of commercial pure Mg were investigated. Interdependence model and solute paradigm theory were applied to evaluate the grain nucleation and growth for these two alloy systems. Both Mn and Zn can refine the grain of pure Mg. Compared to Mg–Zn, the nucleant particl...

Der Werkstoff Stahl hat sich bei der Konstruktion von Automobilen insbesondere aufgrund seiner hervorragenden Kombination von Festigkeit und Duktilität in Verbindung mit einer hohen Verfügbarkeit und relativ günstigen Herstellungskosten bewährt. Jedoch sind die Anforderungen an die Auslegung von Automobilen hinsichtlich Leichtbau, Sicherheit und Um...

This chapter focuses on the impact of research with neutrons and synchrotron radiation on a number of materials and processing methods that are characteristic and essential for commercial passenger airplane and light duty car systems, such as lightweight construction and alternative propulsion systems. The synchrotron diffraction technique is a wel...