  Combining spatially resolved X-ray Laue diffraction with atomic-scale
simulations, we observe how ion-irradiated tungsten undergoes a series of
non-linear structural transformations with increasing irradiation exposure.
Nanoscale defect-induced deformations accumulating above 0.02 displacements per
atom (dpa) lead to highly fluctuating strains at ~0.1 dpa, collapsing into a
driven quasi-steady structural state above ~1 dpa. The driven asymptotic state
is characterized by finely dispersed vacancy defects coexisting with an
extended dislocation network, and exhibits positive volumetric swelling due to
the creation of new crystallographic planes through self-interstitial
coalescence, but negative lattice strain.
