ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2025 6 METALS | POLYMERS | CERAMICS EXPLORING PLUTONIUM’S DELTA PHASE Scientists at Lawrence Livermore National Laboratory (LLNL) set a goal to predict the behavior of plutonium in all its phases. Solving the mystery behind the delta-plutonium phase and its abnormal behavior at high temperatures—shrinking instead of expanding—is an important step. In a new study, the researchers demonstrated a model that can reproduce and explain delta-plutonium’s thermal behavior and unusual properties. The model calculates the material’s free energy. “Free energy fundamentally dictates the state of a material, so it is foundational for understanding it,” says scientist Per Söderlind. “An immense amount of effort at LLNL is dedicated to predicting the behavior of plutonium. The confidence in these STUDYING TWINNING IN MAGNESIUM Researchers at the University of Michigan used x-rays to capture the first 3D views of the formation of microscopic structures that can help absorb stress without breaking in a magnesium alloy. The results will improve understanding of the alloy’s complex reaction to mechanical stress. Because magnesium alloys weigh 30% less than aluminum, some car manufacturers have started using them for non-load-bearing parts. If their behavior under stress could be optimized, this could lead to wider use. Deformation twinning in magnesium allows it to stretch in more directions without breaking, creating ductility, but at a certain point too much twinning can create a concentration of defects that causes cracks to form. “We were surprised to find all three twins formed in triple junctions, where three crystals touch, and defects always formed where the twin touches another crystal. This consistency can help us understand twin microstructures to optimize the material lifetime,” says researcher Ashley Bucsek. Before the experiment, the team used a CT scanner to map how crystal grains were oriented within a magnesium alloy sample. Then they selected a specific grain of interest with a good orientation for following the twinning process. Next, they used the European Synchrotron Radiation Facility in France to image the grain of interest at an ultra-high resolution. They then applied three typical car part loads that would stretch the alloy—0.6, 30, and 45 MPa—imaging the sample after each load. “Real-space x-ray images gave us a front-row seat to observe twinning as stress was applied. We literally watched the twin appear and evolve with our own eyes for the first time,” says doctoral student Sangwon Lee. The next step is to capture changes in real time. umich.edu. Sangwon Lee prepares a magnesium alloy sample for darkfield x-ray microscopy to understand deformation twinning. Courtesy of Ashley Bucsek/Michigan Engineering. Delta-plutonium has been found to have unusual thermal properties. Courtesy of Pixabay/CC0 Public Domain. Boston Metal raised $51 million in new capital from existing investors. Funds will support deployment of the company’s critical metals plant in Brazil, slated to come online in mid-2026, and also finance continued development of its green steel approach. bostonmetal.com. BRIEF
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