The folks at SIMLab know better than anyone how aluminium grains behave under attack. Because of that, they decided that brand new SFI CASA needs expertise on atomic level. Randi Holmestad’s expertise.
Aluminium grains are tiny. There are as many in one cubic millimetre as there are sand grains on a beach. In working with these aluminium grains, SIMLab realized that they needed to learn more about the details inside the grains. There were indications that lower scale matters. The logical consequence is that studies down to atomic level are needed to establish material properties with greater certainty.
Studying details in the microstructure – such as particles, precipitates, dislocations and grain boundaries – gives a better understanding. This in turn will help with experiments, simulation and modelling as basis for innovation.
Enter Professor Holmestad and her team at the NTNU Department of Physics. They possess a ~20 million NOK state of the art transmission electron microscope (TEM) allowing studies down to 0.06 nanometre. The distance between atoms in materials is in the order of 0.2 nanometres, so only now will the researchers be able to study in detail what happens to the atom structure when the materials are subjected to impacts like collisions, explosions and the like. The same goes for temperature changes. Oil rigs in arctic waters is one of the many areas where such knowledge will become increasingly important.
Randi Holmestad runs. Literally. If colleagues observe her walking in the corridor, they will pop out of their office and ask if something is wrong.
Running can bring you pretty far. In 1998, at 30, Randi became the youngest female professor of the university. A few years later, her supervisor fell ill and she had to step up as group leader. Since then she has guided 52 master’s students and 13 PhD candidates through thick and thin. Two years ago her department acquired the world class microscope as part of the NORTEM large scale infrastructure project, where NTNU collaborates with SINTEF and the University of Oslo. Starting now, SFI CASA will be able to share the benefits. Emil Christiansen, the first PhD candidate on this task, is already at it with a thesis on precipitate microstructures.
If Professor Holmestad is new to CASA, she is by no means new to aluminium or to external partners. Norwegian aluminium producer Hydro has a decades-long relationship with NTNU Physics and depends on its scientific results to keep up front. Part of the current cooperation through the “Hydro Road Map” scheme was developed in the tripartite relation between Hydro, SINTEF and NTNU. CASA director Magnus Langseth was one of the creators. Holmestad is one of many who has contributed on the way and is the proud holder of a patent on an aluminium alloy.
“I feel privileged for taking part. This kind of long-term cooperation has huge, mutual benefits,” she says.
Likewise, she has cooperated with CASA research partner SINTEF for years and years. She thoroughly enjoys the exchange:
“It’s rewarding when partners like Hydro, Benteler and SAPA need input.”
In its pure form, a piece of aluminium is bendable with pure manpower. The application value starts when alloying with silicon, magnesium, zinc, copper, silver, germanium and other metals, where only a percent or two dramatically changes the characteristics of the material. In age hardenable aluminium alloys this is due to nano sized precipitates – small needles precipitating all over the place in the alloy, which you can observe in the microscope. As is the case for any bun in the oven, time and temperature are crucial factors.
In Holmestad’s case, she admits a special weakness for one of the alloying atoms:
“I’m particularly fascinated by the copper atoms.”
At the moment, Holmestad is working on a project that seeks to reduce the alloying content of extruded and rolled aluminium without loss of strength.
“By smart alloy design, we can reduce the total solute, the alloys can be easier processed and Hydro saves money.”
As far as necessary
Holmestad’s role in CASA will be to go as far down in detail as necessary, not further. There, she and her collaborators will try to establish what is needed to make more suited materials for any given purpose; be it construction details that might be applicable in the new government headquarters in Oslo, a car part or another industrial application.
With time, the findings will be added to the SIMLab Tool Box for the partners to use.
CASA’s newly recruited professor has remained faithful to Trondheim and NTNU throughout her career, with the exception of four half-year visits to US universities in Arizona and Illinois.
She’s run since childhood. Early on she was attracted to orienteering. Now she’s taken up the activity, but at a more modest level. And of course, she still runs in the corridors.
This article was originally published on SFI CASA’s Newsletter.