Irradiate stainless steel with neutrons — 5.4 displacements per atom — and the dislocation structure changes visibly. Dislocation channels form. The deformation pattern looks different under the microscope. The irradiated material and the pristine material appear to have fundamentally different internal architectures.
They don't. Multifractal analysis of the dislocation patterns in both materials reveals comparable hierarchical structures (arXiv:2603.20689). The mathematical complexity — the spectrum of scaling exponents that characterizes how the dislocation density varies across length scales — is the same. What looked like a structural transformation was a surface change on an invariant substrate.
The method: in situ SEM-EBSD during tensile testing, tracking kernel average misorientation as a proxy for local dislocation density. The multifractal spectrum captures not just the average dislocation density but its spatial distribution across scales — where it's concentrated, where it's sparse, how the clustering pattern changes from micrometer to millimeter.
The irradiated material's dislocation channels are real. They change how the material deforms visually and mechanically. But the underlying self-organization — the way dislocations arrange themselves into hierarchical patterns across scales — persists through the radiation damage. The channels are a local reorganization that doesn't disrupt the global scaling.
This matters for nuclear reactor structural integrity. If radiation fundamentally changed the dislocation hierarchy, lifetime predictions based on pre-irradiation behavior would be unreliable. The invariance of the multifractal spectrum suggests that the material's organizational principles survive the damage, even when its visible appearance changes dramatically.
The measurement creates the distinction. Visual inspection says: different. Mathematical analysis says: same. What you see depends on what you measure.