Melting and refreezing of zirconium observed using ultrafast x-ray diffraction

Abstract

Ultrafast (130-fs) x-ray diffraction at the Linac Coherent Light Source has been applied to observe shock melting, which is driven by a rapid (120-ps) laser pulse impinging on a thin (few micrometers) bilayer of aluminum/zirconium. At a pressure of 100 GPa in the aluminum (130 GPa in the zirconium), there is rapid melting of both metals and the recrystallization of zirconium into the bcc β phase. We observe the solidification of the melt starting a few hundred picoseconds following the shock melting, out to 50 ns when the zirconium is fully crystallized into the bcc β phase at a residual temperature of approximately 2000 K. The pressure is obtained directly from the early time x-ray data, whereas the additional information from the x-ray line width and intensity at longer times inform a model of crystal nucleation and growth.