This film concludes the series "In Profile", with which we presented 12 of our graduates.

Click here for the film about Christina Plump

"And this poses the first challenge, because in order to infer the stress, a reference surface is required. Stress is the force per surface," explains Heike Sonnenberg. And the cross-sectional area of a sphere is not constant over its height. It is also difficult to measure the strain of a sphere that is only millimeters in size.

In subproject D01 Heike Sonnenberg has therefore developed a simplified test method, the micro compression test. This method provides different values than the classical tensile test. The micro compression test on spherical samples is used to determine so-called descriptors, from which conclusions can also be drawn about the strain, compression or even the stress in the material under mechanical stress.

Heike Sonnenberg wanted to investigate the relationships between these descriptors and the classical characteristic values of a tensile test in more detail using the example of the rolling bearing steel 100Cr6. Her initial question was: Do the descriptors from the compression test on spherical micro-samples show a comparable development as a function of tempering temperatures as the conventionally determined tensile strength?

She was able to use the now proven high-throughput method of the CRC to quickly obtain and investigate microspecimens in different, specially adjusted states (colorations). The rapid heat treatment and descriptor-based mechanical characterization within the CRC led to a very high time saving compared to conventional materials testing. Within a very short period of time, she was able to perform comparative mapping for the results of her experimental study and found that similar sensitivities could be identified for the stress descriptor from micropressure testing as described in the literature for the material property tensile strength for the selected section of heat treatment. The trend therefore points in the same direction.

"Of course, more in-depth research is needed here," says Heike Sonnenberg, "but we are pleased to see that we have made an important step forward with the transfer of the descriptors determined to the macroscopic material properties.

She has now published the results of her work in the Open Access journal Materials

For this purpose, she not only uses the data generated in the SFB, but also combines various sources of knowledge to find possible connections that have not yet been discovered.

Mareike loves working in science. People who have ideas and enjoy research create a positive working environment for her. She was also able to experience this on the other side of the ocean - for three months, she spent three months in the USA with other scientists* investigating the new field of materials science and AI.

Ingmar Bösing has already devoted himself to electrochemical characterization in his master's project. He is now working in subproject D03 as one of our graduate students and is ready to take on any challenge - always with the goal of determining the electrochemical properties of materials as quickly as possible. To this end, he investigates aspects of the corrosion behavior of SFB microsamples.

But Ingmar also sees making the principles of science and technology tangible to others as a great addition to his research. Several times he has already been in our profile class at school in colored states and has been able to inspire students there for electrochemistry.

Movie Mareike Picklum

Movie Ingmar Bösing

Both scientists from the field of artificial intelligence were able to impress with their specialist publications.

Michael Beetz occupies 4th place in the robotics category: "One of our special features is the holistic approach we take to robotics and artificial intelligence," he explains. "We combine the classic methods of AI with very powerful new methods such as machine learning to make systems more robust." The goal: to design the AI systems in such a way that their procedure is understandable and explainable at all times, says Beetz.

In addition to Rolf Drechsler, he is an associate subproject leader of P01 and plans to become involved in the SFB "Farbige Zustände" with another subproject for phase 2.

Rolf Drechsler is represented in the Chip Technology category. He is head of the subprojects P01 and P02. While TP P01 deals with the predictor function and data modelling of experimental data sets, TP P02 is responsible for heuristic, statistical and analytical design of experiments. Based on the respective state of knowledge and its uncertainties, TP P02 develops experimental designs for the determination of micro-process parameters leading to the desired material properties.

The SFB is pleased to have these influential scientists in its midst and congratulates them on this award.

Press Release of the University of Bremen

Laser deposition welding, also known as Laser Metal Deposition (LMD), is a type of 3D printing. Large components and very fine structures can be printed with this large device using a powder-based manufacturing process for metals. Multiple powder conveyors used in parallel allow different metals to be used in one operation and many samples to be produced at high speed - faster and more targeted material development. The production, coating, repair and modification of 3D components is of great value to a wide range of industries and it is now impossible to imagine Bremen as an industrial location without it.

Lutz Mädler, spokesperson of the CRC 1232, is pleased: "This large-scale instrument is an ideal tool for flexible and particularly fast sample generation and will open up completely new possibilities for the CRC 1232".

In the future, this modern measurement technology will be integrated into the joint basic research of the Collaborative Research Centre (CRC) and used together with various departments of the University of Bremen, the Leibniz Institute for Materials-Oriented Technologies (IWT) and the BIAS- Bremen Institute for Applied Beam Technology.

From CRC 1232, Lutz Mädler, Nils Ellendt, Rolf Drechsler, Matthias Steinbacher and Frank Vollertsen were involved in the application for this large-scale equipment initiative.

Further information can be found here.

Ilya Bobrov studied in Russia and was in the process of doing an internship at the IWT when he heard about the SFB 1232, which had just been approved at the time, and was immediately interested in a position in the D01. It was always clear to him that he wanted to work in the natural sciences. His favourite subjects, chemistry and physics, are an ideal combination for his studies and work in materials science. And even after work is over, he is still out and about in the - albeit liquid - field of materials research: he brews his own beer.

Click here for the film about Arne

Click here for the film about Ilya

 "With its research on high-throughput processes, the SFB is also making a name for itself beyond the boundaries of its subject area. The publication of the paper in 'High-Throughput' also attests to the success of the application of these methods in the SFB," said Matthias Steinbacher commenting on the publication.

The paper was published as OpenAccess and is available at

https://www.mdpi.com/2571-5135/8/4/22

The solidification of a molten metal determines the structural properties of the material that is later produced. Nowadays, ultra-fine microstructures can be produced by using rapid solidification processes. "The faster the cooling, the finer the microstructure," Malin explains in conversation.  Well-known examples are the production of metal powders and particles by atomization processes or single drop generators. Since Malin Kähnlein had attended a lecture with Nils Ellendt during her studies, she knew that there was a single drop generator of this type in subproject U01. Here she carried out some of her experiments and cooled her AlCu droplets by a targeted drop impact. For this purpose, she chose short drop distances so that the droplets collide with a copper plate at only low speed and thus take on the shape of a hemisphere. This impact mode is new compared to "Splat quenching", in which the drop is partially splattered and has a very flat, irregular and jagged shape after impact.

Another rapid solidification process for the production of near-net-shape components is additive manufacturing using SLM (selective laser melting). However, finding and optimizing new alloys for this process is particularly complex at the current state of the art, as the complex interaction between powder properties, alloy and process control must be taken into account. Here Malin has used a laser to melt and solidify conventionally produced particles from an atomization process and particles about ten times the size from a single drop generator on a substrate using the SLM process, and compared the resulting microstructures. Here, she has determined process windows in order to determine processability properties that can be transferred to the powder on the particles from the single-drop process, which are much easier to produce.

Part of her results can now be used in research to develop a new high-throughput process for evaluating new alloys for additive production. With this work, first steps in this direction could be taken for an alloy. The publication of the work in a peer-reviewed journal is already being planned, which makes Malin rightly a little proud.