Christian Klose

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• Dr.-Ing.
• Group Leader at Leibniz Universität Hannover

Additive manufacturing of magnesium alloys shows great potential for producing patient‐specific resorbable implants or lightweight parts. However, due to the reactive behavior, especially in the laser‐based powder bed fusion (PBF‐LB) fabrication process, the processing window to manufacture almost pore‐free parts is narrow compared to other materia...

Although implants have undergone a remarkable development over the past decades, modern implants still show complications that make the improvement of materials necessary. The presented study investigates the load-bearing capacity of an experimental dental implant made of a niobium alloy (Nb1Zr) compared to identical implants made of Ti6Al4V using...

The corrosion behavior of platinum electrodes in cochlear implant (CI) systems is a critical factor affecting their long-term functionality. This study investigated the influence of the surface roughness of the platinum electrodes on their corrosion behavior. The results of in vitro experiments indicate that higher surface roughness tends to accele...

Magnesium alloys pose challenges in additive manufacturing, due to the difference between the melting temperature of magnesium oxide (2825 °C) on the powder particles and the boiling point of metallic magnesium (1093 °C). A promising approach to overcoming the difficulties is the reduction of the thickness of the high‐melting oxide layer on the sur...

The transportation industry aims to improve energy efficiency and reduce CO2 emissions, with a focus on reducing vehicle mass. A key method involves advanced lightweight construction techniques using materials like aluminum alloys. Research is concentrated on developing processes to combine different materials into reinforced hybrid components, suc...

This study aimed to investigate adhesive shear bond strength (SBS) on an ultrafine-grained niobium alloy (UFG-Nb) that is a potential dental implant material. SBS of three adhesive systems combined with three composites to UFG-Nb was compared to corresponding SBS to Ti-6Al-4V and to zirconia. Specimens of the substrates UFG-Nb, Ti-6Al-4V and zircon...

Many metallic implant materials, such as Ti–6Al–4V, contain elements that are now considered to be critical and have high Young's modulus compared to the human bone, leading to stress shielding. Nb–1Zr alloys, which are free of toxic elements and feature Young's modulus closer to human bone, present a promising alternative. The present study invest...

Platinum and platinum-based alloys are used as the electrode material in cochlear implants because of the biocompatibility and the favorable electrochemical properties. Still, these implants can fail over time. The present study was conducted to shed light on the effects of microstructure on the electrochemical degradation of platinum. After three...

Lightweight design and hybrid components enable innovative and new component concepts, especially when combining structurally reliable metal components with individualized polymer components. In this research, a process for additive manufacturing polymers on the surface of extruded aluminum profiles is examined. The extrusion process is adapted to...

In early innovation phases, the monetary evaluation of process innovations is a challenge for companies due to a lack of data. However, an innovation evaluation is essential in an early innovation phase to ensure that process innovations deliver economic value added (EVA) in early innovation phases and to channel technology transfer expenditures in...

Fragestellung: Der DFG-geförderte Sonderforschungsbereich SFB/TRR 298 „SIIRI“ (Projektnummer 426335750) beschäftigt sich unter anderem mit der Entwicklung neuer Implantate zur Steigerung der Implantatsicherheit. In einem der Teilprojekte wird ein dentales Implantat aus einer experimentellen Nioblegierung (UFG-Nb) entwickelt, aus dessen Inneren beha...

In this study, the thermal conductivity ( κ ) of Al–Cu eutectics were investigated by experimental and computational methods to shed light on the role of these compounds in thermal properties of Al–Cu connections in compound casting. Specifically, the nonequilibrium molecular dynamics (MD) method was utilized to simulate the lattice thermal conduct...

A metallurgical joint between aluminum and copper established by compound casting provides for high thermal conductivity, which is required for lightweight cooling solutions in applications such as high-power light-emitting diodes or computer processors. If casting is employed in a silane-doped inert gas atmosphere whose oxygen partial pressure is...

Compound cast heat sinks have various advantages over conventionally manufactured ones, but oxides present on the metals and formation of a brittle intermetallic layer (IMC) make casting difficult. In the present study, a novel approach was used that employs a silane-doped argon environment to overcome these issues. Oxidation could be fully suppres...

The combination of aluminium (AlSi1MgMn) and titanium (Ti6Al6-4V) allows producing components with high lightweight potential and at the same time high strength and chemical resistance. Upon joining of dissimilar materials, intermetallic phases (IMP) can form. These are comparatively hard and brittle and represent a weak point in the hybrid compone...

The magnesium alloy LAE442 showed promising results as a bone substitute in numerous studies in non-weight bearing bone defects. This study aimed to investigate the in vivo behavior of wedge-shaped open-pored LAE442 scaffolds modified with two different coatings (magnesium fluoride (MgF 2 , group 1)) or magnesium fluoride/calcium phosphate (MgF 2 /...

Novel aluminum-copper compound castings devoid of oxide layers at the interface between the joining partners were developed in order to increase the thermal conductivity of the hybrid component. Due to the natural oxide layers of both aluminum and copper, metallurgical bonds between such bi-metal castings cannot be easily achieved in conventional p...

To combine the advantages of two materials, hybrid bulk metal workpieces are attractive for subsequent processes such as metal forming. However, hybrid materials rely on the initial bond strength for the effective transfer of applied loads. Thus, a non-destructive evaluation of the bonding along the production process chain is of high interest. To...

Grinding tools can be manufactured from metal, vitrified, and resin bond materials. In combination with superabrasives like diamond grains, metal-bonded tools are used in a wide range of applications. The main advantages of metal over vitrified and resin bonds are high grain retention forces and high thermal conductivity. This paper investigates th...

Within the framework of the Collaborative Research Center 1153, we investigated novel process chains for the production of bulk components with different metals as joining partners. In the present study, the co-extrusion of coaxially reinforced hollow profiles was employed to manufacture semi-finished products for a subsequent die-forging process,...

Magnesium has mechanical properties similar to those of bone and is being considered as a potential bone substitute. In the present study, two different pore sized scaffolds of the Mg alloy LAE442, coated with magnesium fluoride, were compared. The scaffolds had interconnecting pores of either 400 (p400) or 500 µm (p500). ß-TCP served as control. T...

Metal foams are attractive for lightweight construction in the automotive sector since they provide high-energy absorption and good damping properties, which is crucial, e.g., for crash structures. Currently, however, foams are produced separately and then pasted into the components. Consequently, the overall mechanical properties depend significan...

Porous magnesium implants are of particular interest for application as resorbable bone substitutes, due to their mechanical strength and a Young's modulus similar to bone. The objective of the present study was to compare the biocompatibility, bone and tissue ingrowth, and the degradation behaviour of scaffolds made from the magnesium alloys LAE44...

Given the complex process condition, extruded aluminum (Al) alloy tubes show locally pronounced differences in microstructure and mechanical properties, which can be influenced by subsequent heat treatment. In the present study, cyclic indentation tests (CITs) were conducted on extruded Al alloy EN AW-6082 to locally determine hardness and cyclic h...

The current study presents a novel Tailored Forming process chain developed for the production of hybrid bearing bushings. In a first step, semi-finished products in the form of locally reinforced hollow profiles were produced using a new co-extrusion process. For this purpose, a modular tool concept was developed in which a steel tube made of a ca...

Additive manufacturing (AM) has become increasingly important over the last decade and the quality of the products generated with AM technology has strongly improved. The most common metals that are processed by AM techniques are steel, titanium (Ti) or aluminum (Al) alloys. However, the proportion of magnesium (Mg) in AM is still negligible, possi...

Metal forming of shape memory alloys (SMA) can be challenging since these are very often brittle due to their intermetallic character. However, formability is often needed not only for realising the desired geometry but also for tailoring the microstructure and the functional properties. To investigate whether the encapsulation in a steel shell can...

The current study introduces a method for manufacturing steel-aluminum bearing bushings by compound forging. To study the process, cylindrical bimetal workpieces consisting of steel AISI 4820 (1.7147, 20MnCr5) in the internal diameter and aluminum 6082 (3.2315, AlSi1MgMn) in the external diameter were used. The forming of compounds consisting of di...

Degradable bone substitutes like Mg-based alloys are promising due to their good osseointegration and biocompatibility. The objective of this study was to investigate the influence of additional coatings on the degradation behavior, osseointegration and gas release of 128 open porous scaffolds (Ø 4 mm, length 5 mm) of the magnesium alloy LAE442 (4...

The reinforcement of light metal components with steel allows to increase the strength of the part while keeping the weight comparatively low. Lateral angular co-extrusion (LACE) offers the possibility to produce hybrid coaxial profiles consisting of steel and aluminum. In the present study, the effect of the process parameters temperature, contact...

This contribution deals with the numerical investigations to develop a novel process chain for hybrid solid components using Tailored Forming. For manufacturing a hybrid bearing bushing, co-extrusion is the first step to produce hybrid semi-finished workpieces followed by a die forging process, machining processes and hardening. Combining aluminium...

In order to reduce the weight of vehicles and their CO2-emissions and to increase driving range, new ways of producing hybrid material compounds must be developed to tailor the properties of the part exactly to the intended use. Lateral angular co-extrusion (LACE) offers the possibility to produce hybrid profiles. In the past, this process was used...

A novel co-extrusion process for the production of coaxially reinforced hollow profiles has been developed. Using this process, hybrid hollow profiles made of the aluminum alloy EN AW-6082 and the case-hardening steel 20MnCr5 (AISI 5120) were produced, which can be forged into hybrid bearing bushings by subsequent die forging. For the purpose of co...

Degradable bone substitutes made of magnesium alloys are an alternative to biological bone grafts. The main advantage is that they can be manufactured location- and patient-specific. To develop and scale appropriate implants using computational models, knowledge about the mechanical properties and especially the change in the properties during the...

The magnesium alloy LAE442 emerged as a possible bioresorbable bone substitute over a decade ago. In the present study, using the investment casting process, scaffolds of the Magnesium (Mg) alloy LAE442 with two different and defined pore sizes, which had on average a diameter of 400 μm (p400) and 500 μm (p500), were investigated to evaluate degrad...

If bone defects occur, the body’s own healing mechanism can close them below a critical size; for larger defects, bone autografts are used. These are typically cut from the same person’s hip in a second surgery. Consequently, the risk of complications, such as inflammations, rises. To avoid the risks resulting from the second surgery, absorbable, o...

The application of monomaterials is limited in lightweight construction concepts, because in addition to the weight requirements, the thermal and mechanical demands are constantly increasing. In order to ensure that the right material is used in the right place, the Collaborative Research Centre (CRC) 1153 is concerned with research into innovative...

Growing demand for individual and especially complex parts with emphasis on biomedical or lightweight applications enhances the importance of laser powder bed fusion. Magnesium alloys offer both biocompatibility and low density, but feature a very high melting point of oxide layers while the evaporation temperature of pure magnesium is much lower....

The development of degradable bone implants, in particular made of metal materials, is an emerging field. The advantage of degradable implants is that they do not have to be removed later. In order to be able to develop and scale appropriate implants for different applications, it is necessary to know the change in mechanical properties of the impl...

Porous magnesium implants have been investigated for some time for their orthopaedic applicability as resorbable bone substitutes. The objective of this study was to evaluate the in vivo degradation behaviour and osseointegration of open-pored scaffolds made of the two magnesium alloys, LAE442 (n = 40) and Mg-La2 (n = 40). Cylindrical magnesium sca...

Undergoing the Tailored Forming process chain, coaxial aluminium-steel profiles joined by co-extrusion are formed into hybrid bearing bushings by die forging. During the joining of aluminium and steel, intermetallic phases may develop. As these phases are very hard and brittle, it is important to be able to predict the width of the resulting interm...

A future trend for machine components like rolling element bearings is the application of multi-materials for manufacturing. In order to manufacture such components with appropriate quality, a new process chain called Tailored Forming was set up. Within this process chain, joined semi-finished work pieces are utilized and formed, followed by a fini...

Large bone defects or fractures must be treated with an implant or transplant. Resorbable implants are attractive as these require only one surgery, whereas bone autografts, which can be cut off from the same person's hip, require more than one procedure. Moreover, porous structures promote the ingrowth of the patient's bone. Thus, the objective of...

Computational modelling is a promising and ethical reasonable method in implant development. A computational model for bone ingrowth on implant level length scale has been implemented and applied for an open‐pored space‐filling bone substitute. First numerical simulations showed reasonable results for the average bone density and the effective Youn...

The use of lightweight materials is one possibility to limit the weight of vehicles and to reduce CO2 emissions. However, the mechanical properties and weight-saving potential of mono-materials are limited. Material compounds can overcome this challenge by combining the advantages of different materials in one component. Lateral angular co-extrusio...

In the information age, the storage and accessibility of data is of vital importance. There are several possibilities to fulfill this task. Magnetic storage of data is a well‐established method and the range of materials used is continuously extended. In this study, the magnetic remanence of thermally sprayed tungsten carbide–cobalt (WCCo)‐coatings...

In order to save weight and costs, different materials can be combined within one component. In the novel process chain being developed within the Collaborative Research Centre (CRC) 1153, joined semi-finished workpieces are used to produce hybrid solid components with locally adapted properties. Different materials are joined in an initial step be...

High-pressure die compound casting relies on high bond quality, and high thermal contact conductance at the interface is a key issue in the context of cast advanced cooling components, such as lightweight heat sinks for desktop and portable computers. The current study aims at enhancing the thermal contact between a copper insert piece and an AlSi9...

The process of cyclic bending was investigated using thin sheets of the magnesium alloy AZ31 and α-titanium. These materials possess an hcp crystal lattice with different c/a ratios. It turned out that the latter have a substantial influence on the sheet deformation behavior. Even for small deformations (up to 2% strain), a large influence on the y...

The combination of light metals and steels allows for new lightweight components with wear-resistant functional surfaces. Within the Collaborative Research Centre 1153 novel process chains are developed for the manufacture of such hybrid components. Here, the production process of a hybrid bearing bushing made of the aluminium alloy EN AW-6082 and...

Within the scope of the Collaborative Research Centre (CRC) 1153 novel process chains for the production of hybrid solid components by Tailored Forming are developed at the Leibniz Universität Hannover. The combination of e. g. aluminium with steel allows to produce hybrid compounds with wear-resistant functional surfaces and reduced weight. In the...

Sheet metal forming is an inherent part of todays production industry. A major goal is to increase the forming limits of classical deep-drawing processes. One possibility to achieve that is to combine the conventional quasi-static (QS) forming process with electromagnetic high-speed (HS) post-forming. This work focuses on the finite element analysi...

In the case of bone defects, there are two different methods to close such defects. One option is to use bone autografts, but therefore the bone graft has to be cut off from the same person’s hip. In this case the patient has to undergo an additional surgery, which bears complications, like causing inflammations. Absorbable, open-pored implants min...

Magnetic magnesium alloys have inherent magnetic properties due to the alloying element cobalt. Thus, the entire structural component made from such an alloy can be utilized for mechanical load measurements using the harmonic analysis of eddy current signals. Because the solubility of cobalt in the magnesium matrix is negligible, the magnetic prope...

Neodymium containing magnesium alloys like MgNd2 and ZNdK100 offer high corrosion resistance and biocompatibility due to low amounts of alloying elements, and are thus attractive for biomedical applications. Compared with common bioresorbable magnesium alloys, which frequently contain mischmetal, the use of neodymium as a single rare earth element...

The magnetic properties of lightweight alloys based on magnesium and cobalt offer a novel way to measure mechanical loads throughout the entire structural component using the magnetoelastic effect. Since the solubility of cobalt in the magnesium matrix is negligible, the magnetic properties mainly originate from Co-rich precipitates. Size and distr...

Im Fokus dieses Fachbeitrags steht die im Rahmen des Sonderforschungsbereichs 1153 angestrebte Entwicklung einer Prozesskette zur Fertigung einer hybriden Lagerbuchse aus Aluminium und Stahl. Es werden die Werkzeugkonzepte zur Halbzeugherstellung durch das Verbundstrangpressen sowie zum anschließenden Gesenkschmieden der hybriden Lagerbuchse vorges...

The formability of deep drawing can be extended by combining it with a subsequent high-speed forming method such as electromagnetic forming. However, up to now, no sufficient systematic understanding of the underlying principles or of a succesful design of such coupled processes has been gained. Hence, in this work, a methodology for the analysis a...

In this analysis, a Selective Laser Melting (SLM) is used to contribute within machine elements manufacturing by using aluminium base alloys. It shows the ability to produce hybrid components which composite of different parts with different materials, and lightweight components with internal structure. An investigation to the mechanical and struct...

The magnesium-neodymium alloy MgNd2 offers an elongation of 30%. Therefore, it is well suited as a material for resorbable stents which can be used for treating chronic sinusitis. While the alloy’s corrosion properties were already investigated in vitro, the present study focuses on the in vivo degradation behavior of fluoride-coated and uncoated s...

The magnesium-neodymium alloy MgNd2 offers an elongation of 30%. Therefore, it is well suited as a material for resorbable stents which can be used for treating chronic sinusitis. While the alloy’s corrosion properties were already investigated in vitro, the present study focuses on the in vivo degradation behavior of fluoride-coated and uncoated s...

The focus of this paper is on the process chain development that is being researched within the Collaborative Research Centre 1153 for the production of a hybrid bearing bushing made of aluminium and steel. Here, the tool concepts for the production of semi-finished products through compound extrusion and the subsequent forging to a hybrid bearing...

The present study focuses on the influence of longitudinal and charge weld seams on the possibility for their non-destructive testing in extruded profiles. For this, aluminum and magnesium alloys were extruded at different extrusion conditions using porthole dies and prepared for non-destructive testing. First, the electrical conductivity of profil...

Biodegradable and biocompatible magnesium alloys appear to be very promising not only for temporary clinical application but also for developing deformable and degradable medical implants. This study analyzes the in vivo degradation behavior and the impact on the paranasal sinuses of the highly ductile Mg-2 wt%Nd alloy (MgNd2) in order to provide a...

The frontal sinus recess consists of anatomically narrow passages that are prone to stenosis in endonasal frontal sinus surgery for chronic sinus disease. Over the past 100 years, diverse frontal sinus stents have been developed and evaluated in clinical and animal studies. However, superinfection, formation of granulations tissue, stent dislocatio...

The inherent magnetic properties of lightweight alloys based on magnesium and cobalt offer a novel way in order to measure mechanical loads throughout the entire structural component using the magnetoelastic effect. Because the solubility of cobalt in the magnesium matrix is negligible, the magnetic properties mainly originate from Co-rich precipit...

The combination of different light alloys enables lightweight solutions with tailor-made properties at the macroscopic global as well as at the microscopic scale. In this context co-extrusion by Equal Channel Angular Pressing (ECAP) offers a great potential for advanced profiled structures. While titanium alloys show particular high mechanical stre...

The inherent magnetic properties of lightweight alloys based on magnesium and cobalt offer a novel way in order to measure mechanical loads throughout the entire structural component using the magnetoelastic effect. Because the solubility of cobalt in the magnesium matrix is negligible, the magnetic properties mainly originate from Co-rich precipit...

Magnetic magnesium alloys have an inherent load-sensitive behavior. These alloys are manufactured by casting of magnesium alloyed with the ferromagnetic element cobalt. In this context, the magnetoelastic effect can be used in order to measure mechanical loads during the component's service by means of a harmonic analysis of eddy current signals. T...

The combination of different light alloys enables lightweight solutions with tailor‐made properties at the macroscopic global as well as at the microscopic scale. In this context co‐extrusion by a lateral angular co‐extrusion (LACE) process offers a great potential for advanced profiled structures. While titanium alloys show particular high mechani...

Effect of low-cycle room-temperature reverse bending on the crystallographic texture, metallo-graphic structure, and mechanical properties of sheets of ZE10 magnesium alloy after hot rolling and annealing has been studied. The initial texture is characterized by a wide scatter of basal poles in the transverse direction. In the process of reverse be...

The application of a pneumatic testing device for the high speed forming of aluminium alloy sheet metal is presented in this paper. Former publications of the authors showed the feasibility of a drop tower test rig for Nakajima testing of sheet metal (EN AW-6082 T6) at punch speeds of approximately 10 m/s or strain rates of approximately 100 s-1. H...

Introduction Experimental Procedures Results and Discussion

To improve the mechanical properties, the castability as well as the corrosion resistance of magnesium alloys, aluminium is frequently employed. As a rule, technically relevant alloys contain between 3 and 9 wt% aluminium. Normally, aluminium contents under 3 wt% is said to have no corrosion reducing effect. In order to investigate the influence of...

This paper describes a novel processing route for the large scale manufacturing of magnesium sheets. This processing route consists of the production of magnesium tubes by hot extrusion with a subsequent forming step. The processing route allows the manufacture of magnesium sheets with enhanced properties compared to those manufactured by conventio...

Zur Verbesserung der Korrosionsbeständigkeit von Magnesiumlegierungen wird vielfach Aluminium als Legierungselement gewählt. Neuere Untersuchungen zeigen, dass alternativ durch Zulegieren geringer Anteile von Zink die Korrosionsrate binärer Magnesium-Zink-Legierungen vermindert werden kann. Basierend auf diesen Ergebnissen wurden niedriglegierte Mg...

In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder r...

In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder r...

Magnetic magnesium alloys can be utilized as a load sensitive material, in which the inverse magnetostrictive effect is used in order to measure the actual loads in structural components manufactured from such lightweight sensor alloys. To achieve a material which exhibits magnetic properties, Mg is alloyed with ferromagnetic materials like cobalt...

Introduction Experimental Results Discussion Conclusions