About

Pascal Bellon is the Donald W. Hamer Professor of Materials Science and Engineering at the University of Illinois at Urbana-Champaign. He earned his PhD in Materials Science from the University of Paris 6, France, and worked for seven years at CEA-Saclay, France before joining the University of Illinois as a tenure-track Assistant Professor in 1996. He was promoted to Associate Professor in 2002 and Full Professor in 2009. Throughout his career, he has received numerous awards including an NSF career award in 1998, multiple Academy for Excellence in Engineering Education awards from the University of Illinois, the Don Burnett teaching award in 2000, the Accenture Engineering council award for Excellence in Advising in 2007, the Stanley Pierce award in 2009, and was named a Racheff faculty scholar in 2012. In 2016, he was inducted as the Donald W. Hamer Professor in Materials Science and Engineering. He also served as interim head of the Department of Materials Science and Engineering at Illinois in 2019. Professor Bellon's research focuses on materials driven into non-equilibrium states by external forcing such as irradiation by energetic particles and plastic deformation, particularly during powder processing and in tribological contacts. His work investigates how these driven systems can self-organize at the nanoscale and self-adapt to improve their performance in service. His research combines experimental and computational approaches to study phenomena such as compositional patterning in irradiated binary alloys, radiation-induced segregation, and microstructural evolution under severe external forces. This research aims to better understand alloys in far-from-equilibrium conditions to advance the development of new materials by design.

Research topics

• Materials science
• Thermodynamics
• Composite material
• Physics
• Chemistry
• Chemical physics
• Metallurgy
• Condensed matter physics
• Crystallography
• Atomic physics
• Mechanics
• Chemical engineering
• Classical mechanics

Selected publications

• Density functional theory-informed design of radiation-resistant dilute ternary Cu alloys

  Physical Review Materials · 2026-03-02

  articleOpen access

  This research establishes a systematic, high-throughput computational framework for designing radiation-resistant, dilute ternary copper-based alloys by addition of solutes that bind to vacancies and reduce their mobility, thus promoting interstitial-vacancy recombination. The first challenge in developing alloys by this method is mitigating the vacancy-mediated solute drag effect, since density functional theory (DFT) calculations show that solutes that bind strongly to vacancies are also rapidly dragged to point-defect sinks, and thus removed from the matrix. To overcome this problem, two types of solutes are added to the Cu matrix: a first solute with a strong vacancy binding energy ($B$-type species) and another solute that binds to ``B'' and is a slow diffuser in Cu ($C$-type species). Using DFT, 21 synergistic solute pairs are screened, with ``B''$=\mathrm{Zr}$, Ge, Sn and ``C''$=\mathrm{Fe}$, Co, Mo, Ni, Nb, W, Cr. Two promising alloys, Cu(Zr,Co) and Cu(Zr,Fe) are then investigated in detail in the dilute regime. Diffusion and solute drag in these alloys are modeled using the kinetic cluster expansion approach (KineCluE) under irradiation conditions. It is shown that strong Zr-``C'' thermodynamic binding, especially between Zr and Co, significantly reduces the mobility of Zr solute and suppresses the vacancy-mediated solute drag. Using an analytical framework for the standard five-jump frequency model for diffusion in binary alloys, it is found that vacancy-Zr-Co triplets disrupt the kinetic circuits that promote solute drag in the binary alloy by raising the dissociation barrier for the vacancy from the solute.

  PublisherOA PDFDOI

• Nonequilibrium defect-phase nanostructures stabilized by irradiation in undersaturated Ni-Si nanocrystalline alloy

  Acta Materialia · 2026-05-12

  articleOpen accessSenior authorCorresponding

  Nanocrystalline thin films of the undersaturated alloy Ni-8.5 at% Si were subjected to 2 MeV Ti irradiation at temperatures ranging from 450°C to 550°C. Correlative microscopy combining transmission electron microscopy (TEM), scanning-TEM and atom probe tomography (APT) revealed that large dose irradiation at 450°C of samples with initial grain sizes below 100 nm stabilized a novel nanostructure which surprisingly contained three co-existing phases, the γ face-centered-cubic (FCC) matrix, γ ′ L1 2 ordered precipitates on intragranular dislocation loops and Ni 31 Si 12 precipitates at triple junctions (TJs). In contrast, irradiation at 550°C and irradiation of larger grain-size samples at 450°C only produced a γ − γ ′ two-phase coexistence. Analysis of the three-phase nanostructure and phase field simulations indicates that radiation-induced segregation is most pronounced at TJs, thus triggering the formation of Ni 31 Si 12 precipitates. These incoherent precipitates, in turn, appear to have contributed to stabilizing the grain size under irradiation. The results are generalized using the concept of driven defect-phases. It is suggested that the stabilization of driven defect-phases may impart radiation resilience by providing localized relaxation modes to the microstructure evolution during and after temporary perturbations in irradiation conditions.

  PublisherDOI

• Nonequilibrium Defect-Phase Nanostructures Stabilized by Irradiation in Undersaturated Ni-Si Nanocrystalline Alloy

  SSRN Electronic Journal · 2026-01-01

  preprintOpen access
  PublisherDOI

• Global self-organization of solute induced by ion irradiation in polycrystalline alloys

  Communications Materials · 2025-03-01 · 3 citations

  articleOpen accessSenior author

  Most materials are brought into nonequilibrium states during processing and during their service life. Materials for nuclear and space applications, for instance, are continuously exposed to energetic particle irradiation, which is often detrimental to materials’ performance. Here we demonstrate, however, that sustained irradiation can induce self-organization of the microstructure of polycrystalline alloys into steady-state patterns and, in turn, improve their radiation resistance. Using an Al −1.5 at.% Sb alloy as a model system, we show using transmission electron microscopy and atom probe tomography that, for nanocrystalline thin films irradiated at 75 °C with 2 MeV Ti ions to large doses, the microstructure consists of finite-size, self-organized AlSb nanoprecipitates inside the grains and along the grain boundaries. Furthermore, this steady state is independent of the initial microstructure, thus self-healing. Phase field modeling is employed to construct a steady-state phase diagram and extend the experimental results to other alloy systems and microstructures. Irradiation of alloys typically introduces changes to the atomic- and micro-scale structure, degrading performance. Here, sustained irradiation of an Al-Sb alloy causes self-organization that stabilizes the microstructure, improving radiation resistance.

  PublisherOA PDFDOI

• A Strategy for Imparting Radiation Resistance to Dilute Alloys Using Synergistic Solutes

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• A strategy for imparting radiation resistance to dilute alloys using synergistic solutes

  Journal of Nuclear Materials · 2025-07-29

  articleOpen accessSenior authorCorresponding

  A novel approach for imparting radiation resistance to dilute alloys is proposed whereby two synergistic solute species are employed, a first one, solute B, that binds strongly to vacancies and a second one, solute C, that binds to solute B and is also a slow diffuser in solvent A. This combination results in B-C solute clusters that are immobile traps for vacancies. These traps promote point-defect recombination over irradiation doses far beyond that achievable in binary alloys, where solutes that strongly bind to vacancies are typically fast diffusers and thus quickly removed from grain interiors by radiation-induced segregation. A parametric study, performed using atomistic kinetic Monte Carlo simulations with realistic metallic solute properties in Cu, reveals that alloy stability under irradiation derives largely from the formation of mixed B-C solute clusters comprised of 10 or more atoms. The solute loss at sinks, moreover, is found to follow stretched exponentials, with the most promising alloys corresponding to values of the stretch exponent β approaching 0.5. The effects of irradiation dose rate and grain size are discussed using simple scaling relationships. Lastly, the approach is illustrated by identifying promising solute combinations in Cu, Ni and Al alloys.

  PublisherDOI

• Additive manufacturing of an ultrastrong, deformable Al alloy with nanoscale intermetallics

  Nature Communications · 2024-06-15 · 60 citations

  articleOpen access

  Abstract Light-weight, high-strength, aluminum (Al) alloys have widespread industrial applications. However, most commercially available high-strength Al alloys, like AA 7075, are not suitable for additive manufacturing due to their high susceptibility to solidification cracking. In this work, a custom Al alloy Al 92 Ti 2 Fe 2 Co 2 Ni 2 is fabricated by selective laser melting. Heterogeneous nanoscale medium-entropy intermetallic lamella form in the as-printed Al alloy. Macroscale compression tests reveal a combination of high strength, over 700 MPa, and prominent plastic deformability. Micropillar compression tests display significant back stress in all regions, and certain regions have flow stresses exceeding 900 MPa. Post-deformation analyses reveal that, in addition to abundant dislocation activities in Al matrix, complex dislocation structures and stacking faults form in monoclinic Al 9 Co 2 type brittle intermetallics. This study shows that proper introduction of heterogeneous microstructures and nanoscale medium entropy intermetallics offer an alternative solution to the design of ultrastrong, deformable Al alloys via additive manufacturing.

  PublisherOA PDFDOI

• Investigation of Radiation-Induced Segregation at Fully Characterized Coherent Twin Boundaries in Proton-Irradiated 316l Stainless Steel

  SSRN Electronic Journal · 2024-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Investigation of radiation-induced segregation at fully characterized coherent twin boundaries in proton-irradiated 316L stainless steel

  Journal of Nuclear Materials · 2024-10-30 · 2 citations

  articleOpen accessSenior author

  • 2 MeV proton irradiated 316L austenitic stainless steel was investigated. • High-angle and twin boundaries were selected and evaluated. • RIS was measured with STEM-EDS and analyzed via an elemental excess calculation. • RIS was detected at coherent Σ3 < 110>{111} twin boundaries. • From 2.3 – 4.2 dpa, RIS levels were similar for all investigated grain boundaries. The effect of grain boundary character on radiation-induced segregation (RIS) is investigated in a 316L austenitic stainless steel irradiated with 2 MeV protons at 360 °C. Orientation imaging microscopy is employed to select specific grain boundaries (GBs), including Σ3{111} coherent twin boundaries, fully characterized by a five-degree of freedom analysis, as well as high angle GBs. Chemical maps along these GBs below the irradiated surface, at depths corresponding to damage levels ranging from 2.3 dpa to 4.2 dpa, are acquired using energy-dispersive spectrometry in a scanning transmission electron microscope (STEM-EDS). RIS levels are defined as elemental GB excess quantities and are used to compare RIS at twin boundaries and high-angle GBs. These measurements are complemented by the analysis of void distributions near GBs and by characterizing the structure of coherent twin GBs prior to and after irradiation using high-resolution STEM imaging. In light of the results obtained in this work, the evolution of the efficiency for point defect elimination of coherent twin GBs with the irradiation dose is discussed.

  PublisherDOI

• Grain Boundary Precipitation and Self-Organization in Two-Phase Alloys Under Irradiation: Phase Field Simulations and Experiments in Al-Sb

  JOM · 2024-04-24 · 2 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

Recent grants

• Mechanical Mixing in Metallic Alloys During Ball Milling and Sliding Wear

  NSF · $412k · 2003–2008

• Radiation resistance in alloys by solute-defect trapping

  NSF · $450k · 2017–2021

• MRI: Acquisition of a state-of-the-art atom probe for three-dimensional imaging and analysis of materials

  NSF · $1.6M · 2018–2021

• Control of Kinetic Processes in Irradiated Alloys through Compositional Patterning

  NSF · $561k · 2008–2013

• Self-Organization in Model Cu Alloys for High-temperature Irradiation Environments

  NSF · $600k · 2013–2018

Frequent coauthors

• G. Martin

  Nota Laboratories (United States)

  89 shared

• R. S. Averback

  University of Illinois Urbana-Champaign

  81 shared

• F. Soisson

  46 shared

• Y. Grandjean

  Électricité de France (France)

  28 shared

• Raúl A. Enrique

  University of Michigan–Ann Arbor

  20 shared

• Yinon Ashkenazy

  17 shared

• Nhon Q. Vo

  17 shared

• Manuel Athènes

  16 shared

Labs

• Bellon-GroupPI

  Materials driven into non-equilibrium states by external forcing such as irradiation by energetic particles and plastic deformation, in particular during powder processing and in tribological contacts, and on investigating how these driven systems can self-organize at the nanoscale and self-adapt to improve their performances in service.

Awards & honors

• NSF Career Award (1998)
• Awards from the Academy for Excellence in Engineering Educat…
• Don Burnett Teaching Award in 2000