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I often use this analogy to cooking.
You want to get a certain texture and and a certain taste.
And in the case of metals production it's the same thing.
You add a little bit of iron and a little bit of manganese and a little bit of titanium
and maybe a little bit of carbon to get a set of properties that you want
fatigue resistance failure resistance, strength and ductility, formability and so forth.
In our lab there is a specific focus on what we call healing or self-healing of metals.
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We use steels and aluminum alloys and titanium alloys in cars and constructions,
in planes, even in our bodies, so we use implants.
We want lighter cars, but at the same time we want cars that are safer.
We want planes that have longer lifetime and can carry more people in a single run.
But on top of it, there are also environmental challenges
and this is one of the things that we in my group focus on.
If we want to cut down carbon dioxide emissions
we cannot rely solely on processing solutions
we have to rely also on material solutions.
In other words we, have to find ways of using less metals
and we have to find ways of using metals that go for a longer time.
Sort of an extreme example that I like is Mars expedition for instance.
Think about the days when this is possible.
We won't be able to carry tons of steel from Earth to Mars.
And there also these kind of healing or resetting concepts would be very critical.
Once we produce these alloys that we designed based on our healing or resetting concepts
we of course want to characterize these materials.
Then then we have a better understanding of how we can manipulate these microstructures.
In a traditional lab you use relatively larger rigs and carry out experiments
then you look at the microstructure.
We hear in in my lab follow a different approach when we use what is called
in situ techniques so that we gather information about both the mechanical response
and information about the micro structural response at the same time
so that we can connect these dots.
And to be able to do this we constantly come up with with new techniques for our electron microscope.
For example
most of the materials that we design have nano structures
So individual properties of the structures are very important.
So how do you test these these individual properties? You do this by getting a tiny probe
and being able to do in situ small-scale indentation experiments.
It's like taking a tiny pin and pinching different phases to look at how hard they are and how stiff they are.
When we are shaping metals for different processes
for example you just produce a sheet metal and you want to use it to make the body of a car.
The the way the metal deforms locally is very different than just a normal
actual tension test that we typically do in the lab characterize this behavior.
So locally parts of the metal is being stretched in both directions
parts of the metal are stretched only in one direction
and parts of the metal are bent.
So typically in metallurgical labs these
these strain puff effects are not so much investigated.
So what we do is we carry out what is called bulge tests.
You take a thin sheet of metal, so this is a typical sample
and this is very thin and you clamp it in such a way that you can
apply pressure from the bottom and bulge it.
This is quite an interesting technique because it allows us to stop the experiment at any given time,
take the sample out and bring it back again to our electron microscope.
Because remember one of our main focuses is being able to do things in situ,
being able to track our microstructures evolve under complex boundary conditions.
We want to understand the orientation dependence of damage resistance
and we do this by milling out - micro milling - a shape like a flower, like a star.
And then we put cyclic loads on this material
so that the direction in which the material is most sensitive to the cracking
you would would see that the crack would nucleate and propagate.
And once the crack starts propagating, then we can look at the interaction of this crack
with the surrounding microstructure.
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If we look at our own lives, I see that more and more we lose this capability to reuse things.
I know from my own family that my father is much more capable of repairing things than myself.
And I know from his stories that his father was.
So from a more social perspective
we lose this capability of repair and reuse more and more
and thus I think it's very important for us scientists to show that this is still both scientifically interesting,
and engineering wise, it's also feasible and logical.
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