Scientists track how magnesium alloys deform in unprecedented detail

Alloys, often based on aluminium or iron, enhance the properties of metals, such as strength or corrosion resistance, and are commonly used in many different applications, such as transportation, electronics or construction.

“Until very recently, the manufacturing of alloys was based on trial and error, but we have now tools, such as our beamline, to get a deeper understanding of what microscopic processes occur when you apply thermal or mechanical treatments to an alloy”, explains Carsten Detlefs, scientist in charge of ID03 beamline.

Magnesium has been identified as a promising candidate for lightweight alloys, as it weighs 30% less than aluminum and it has excellent machinability. This weight reduction could lead to lower fuel consumption in conventional vehicles and reduced energy demands in electric cars. It is already currently used in automotive components and casings for laptops or smartphones.

However, in practice, things are not so straightforward. Magnesium has a hexagonal crystal structure, unlike iron or aluminium, which have a cubic structure. When cubic materials deform, they have multiple slip systems, i.e. they can shift around in a ductile way under stress. Magnesium’s hexagonal structure does not always deform smoothly. Under stress, it forms tiny, mirrored regions called deformation twins deep inside its grains. These twins help the metal flex but can also turn into weak points where cracks begin.

The origin of failure

This is where the ESRF’s Dark-field X-ray microscopy beamline comes in. Ashley Bucsek, assistant professor at the University of Michigan and leader of the study, came to the ESRF to analyse the deformation in a single grain of interest in a magnesium alloy. The grain had been selected following laboratory X-ray diffraction contrast. “The ESRF is the only facility with a dedicated, mature beamline exclusively focused on dark-field X-ray microscopy. I have been extremely fortunate to be a user since 2017, giving me a front-row seat to the beamline's evolution and growth. More recently, my team and I have been leveraging the exciting advancements on ID03 to investigate how deformation twinning in one grain can trigger deformation in its neighboring grains”, she said.

The team discovered that deformation twins do not appear randomly; they tend to start at triple junctions, where three grains meet like corners in a crystal puzzle. Once formed, they grow in surprising ways, not just straight ahead, but sideways and irregularly, forming lopsided ellipsoids inside the grain. Even more important, they observed that these twins become hotspots for dislocation pile-up, which are internal stress markers that can eventually trigger cracks.

“We were surprised by these results, because according to conventional theory, the nucleation of twins should be governed by the so-called Schmid factors. We did not know how important the grain boundaries would be”, says Detlefs.

For ESRF scientist Can Yildirim, also involved in the study, “these findings help explain how cracks initiate at the microscopic level, and this knowledge that can inform how we design lighter, more damage-tolerant materials for real-world applications”.

ID03: From a “map of Europe to a road in France”

The development of Dark-field X-ray Microscopy, the defining feature of the ID06-HXM beamline (now ID03), was crucial for the experiment, which enabled Bucsek and the team to analyse in very high resolution a single grain. Until today, scientists relied on optical and electron microscopy to study these kinds of processes, but, unlike X-rays, these techniques only allow for surface analysis or through very thin materials.

In order to understand the capabilities of ID03, Detlefs suggests an analogy of a map: ““Imagine we have a map of Europe that represents the whole alloy; Each country corresponds to a grain inside the alloy. First you need to select which country you are interested in. For this, Bucsek used lab X-ray diffraction. Dark-field X-ray Microscopy on our beamline then allows us to zoom in as much as at a 10km range, so visualising a road in France, for example."

He adds: “Furthermore, we are now implementing the large-scale overview on ID03, such that all steps can be carried out within the same experiment. This enables us to see what the neighbours do, i.e. other countries around France, in our analogy. This was a dream for a very long time, but now it is becoming reality and many users are starting to take advantage of this unique capability”.

This development is part of the objectives of the ERC grant by Can Yildirim "Deformation and Recrystallization Mechanisms in Metals (D-REX)”, which aims to address fundamental questions concerning how recrystallisation impacts local structures and predict initiation sites. 

Tracking deformation live

This was one of the last experiments performed on the original DFXM setup at ID06-HXM. Today, the same microscope has moved to ESRF’s upgraded beamline ID03, equipped with faster detectors, better optics and goniometer, and the high-brilliance beam from the EBS upgrade.

The next step for the team is to conduct time-resolved experiments to watch how twins nucleate and evolve live, across multiple grains, during mechanical loading, not just before and after. These future studies will allow researchers to connect microstructure evolution to real performance, from predicting failure in car chassis to designing magnesium alloys that are not only lighter and greener, but also stronger and safer.

Reference:

Lee, S., et al, Science, 7 August 2025. https://www.science.org/doi/10.1126/science.adv3460

Text by Montserrat Capellas Espuny

Top image: Evolution of the twin morphology inside the parent grain relative to the loading direction (LD).