Ecological and economic aspects nowadays increasingly require the development of weight‐reduced designs and energy‐efficient production processes. Particularly in the field of modern vehicle or aircraft construction, developers endeavour to take into account the ever more extensive customer requirements for safety and comfort by using lightweight construction. In many lightweight construction applications, alongside the classic material steel, plastics and the light metals aluminium, magnesium and titanium are being used. Due to a wide variety of requirements, the combination of different material classes to form hybrids will become even more important in the future. Injection moulding is an established method to join plastic‐metal hybrid components. In the present study, the potentials of electron beam structuring by means of surfi‐sculpt, an electron beam material processing technology, on different lightweight materials for the generation of form‐fit elements in plastic‐metal‐hybrid components to be used to join both materials by overmoulding are analysed. The analysis is performed by means of tensile shear test specimens.

In this work, high-speed thermography is shown to effectively capture quasi-stationary temperature fields during the laser welding of steel plates. This capability is demonstrated for two cases, with one involving the addition of a ferritic-bainitic filler wire, and the other involving the addition of a low-transformation-temperature (LTT) filler wire. The same welding parameters are used in each case, but the temperature fields differ, with the spacing between isotherms being greater in the case where the low-transformation-temperature filler material is added. This observation is consistent with the differences in the extent of the heat-affected zone in each sample, and the shape of the weld pool ripples on the weld bead surfaces. The characterization of temperature fields in this way can greatly assist in the development of novel methods for reducing residual stresses, such as the application of low-transformation-temperature filler materials through partial-metallurgical injection (PMI). This technique reduces or eliminates tensile residual stresses by controlling the temperature fields so that phase transformations take place at the optimum times, and success can only be guaranteed through precise knowledge of the temperature fields in the vicinity of the welding heat source in real time.Keywords: Cooling rate / heat-affected zone (HAZ) / phase transformation / residual stress / temperature measurement / welding thermal cycle In dieser Arbeit wird Hochgeschwindigkeits-Thermographie zur effektiven Dokumentation quasi-stationä rer Temperaturfelder wä hrend des Laserstrahlschweißens von Stahl vorgestellt. Gezeigt wird dies am Beispiel von zwei reprä sentativen Schweißungen, wobei einerseits ein ferritsch-bainitischer Zusatzdraht und andererseits ein Low-Transformation-Temperature-(LTT) Zusatzdraht verwendet wird. In beiden Fä llen werden die gleichen Schweißparameter verwendet. Im Vergleich wird eine merkliche Abweichung der Temperaturfelder deutlich. Bei Low-Transformation-Temperature-Zusatzdraht vergrö ßern sich die Abstä nde zwischen den Iso-Corresponding author: S. Gach, Welding and Joining Institute (

Low-transformation-temperature materials (LTT) are used as high-alloy welding filler material for high-strength steels in order to minimize the tensile stresses and resulting distortion of the component during the welding process. The increase in the volume of the structure produced during martensitic transformation is utilized in order to counteract the volume shrinkage due to the cooling process. As stated in the field of study various elements influence the starting temperature of the martensite transformation, the influence on the volume expansion during the martensite formation is unknown. The influence of alloying elements nickel and chromium on the conversion behavior of low-transformation-temperature materials is to be investigated in detail. In particular, the effect of the variation of the mentioned elements on the starting temperature of the martensitic phase transformation and the extent of the volume expansion associated with that is investigated. In addition, the change in the hardness of the different low-transformation-temperature alloys is recorded and compared.

Titanium-based alloys, for example, Ti6Al4V, are frequently employed for load-bearing orthopedic and dental implants. Growth of new bone tissue and therefore osseointegration can be promoted by the implant's microtopography, which can lead to improved long-term stability of the implant. This study investigates the effect that an organized, periodical microstructure produced by an electron beam (EB) technique has on the viability, morphology, and osteogenic differentiation capacity of human mesenchymal stromal cells (hMSC) in vitro. The technique generates topographical features of 20 μm in height with varying distances of 80-240 μm. Applied alterations of the surface roughness and local alloy composition do not impair hMSC viability (>94%) or proliferation. A favorable growth of hMSC onto the structure peaks and well-defined focal adhesions of the analyzed cells to the electron beam microstructured surfaces is verified. The morphological adaptation of hMSC to the underlying topography is detected using a three-dimensional (3D) visualization. In addition to the morphological changes, an increase in the expression of osteogenic markers such as osteocalcin (up to 17-fold) and osteoprotegerin (up to sixfold) is observed. Taken together, these results imply that the proposed periodical microstucturing method could potentially accelerate and enhance osseointegration of titanium-based bone implants. K E Y W O R D S cellular response, electron beam, microstructure, osteogenic differentiation, stem cells

Low-Transformation-Temperature (LTT) materials are used for residual stress reduction in weld seams and, subsequently, for the prevention of distortion. Typically, LTT materials are highly alloyed Fe-based materials with levels of chromium and nickel that ensure that austenite transforms to martensite at reduced temperatures. The dilatation associated with the transformation is prevented by the surrounding material. Consequently, compressive stresses develop within the transformed region, and these counteract the accumulation of stresses due to thermal contraction. The precise chemistry of the weld metal determines the transformation temperature as well as the magnitude of the volume expansion. The chemical composition of the weld metal can, in turn, be influenced by the energy input during welding. In recent years, LTT-filler materials have been applied successfully in arc welding processes for residual stress reduction. Digital image correlation provides one avenue for the detection of surface displacements or deformations, as they occur during the cooling down process, in the vicinity of a weld. Observation of the movement of surfaces using a stereo camera setup allows the recording of displacements in three dimensions. Technically, this is achieved by identifying recognizable points on the surface under observation and by tracking their movement via comparisons between several time-shifted images. Visualization of surface contractions, as well as the effects of solid-state phase transformations during the joining process, especially during cooling, is key to understanding and influencing the residual stress state in welds as well to reducing distortion. In this study, the used installation setup, and the methodology for sample preparation, shows the production of information relating to surface displacements in the direct vicinity of the laser weld during the cooling down stage. Different welding parameters were investigated, resulting in different dilution levels for the LTT-Filler material, thereby influencing the distances to the weld pool and temperatures at which transformations took place. In order to provide a point of reference, comparable welds, made with conventional filler wires, were also investigated. The displacements after welding are always lower when using an LTT filler wire when compared to a conventional wire, proving that LTT wires can be used to mitigate distortion during laser beam welding.