Response of Ni/Al laminates to laser-driven compression

Ni/Al laminates with bilayer thicknesses in the micrometer (∼5 μm) and nanometer (∼50 nm) range were subjected to exothermic reactions induced by laser-driven compression. The initial shockless compression steepened into shock in the microscaled laminates generating a pressure pulse duration of several tens of nanoseconds, which induced strain rates varying from 107 to 108 s−1. The laser energies applied, 650, 875, and 1305 J, generated peak compression stresses of 30, 75, and 118 GPa, respectively, at the plasma stagnated Al surface. Large differences in flow stresses and bulk compression moduli of Ni and Al introduced shear localization in the Ni/Al interfaces. The nanoscale Ni/Al laminates were fully reacted, producing NiAl with grain sizes less than 500 nm. The NiAl intermetallic phases, B2 (β) phase (fcc) and martensitic phase (bcc), coexist in the NiAl nanograins. It was confirmed that the intermetallic reaction in the Ni/Al microlaminate cannot self-sustain for the short duration, laser-driven compressive loading. The intermetallics NiAl (equiaxed grains) and NiAl3 (dendrites) were identified on the plasma stagnated surface of Ni/Al microlaminates. The distribution of intermetallic phases varied according to the incident laser energies.