Spalling fracture of Ni/Al nanolaminates influenced by chemical reaction

We investigate spalling behaviors of Ni/Al nanolaminates by molecular dynamics simulations. First, we discuss spalling damage distributions in shocked Ni/Al nanolaminates. Voids nucleate in Al layers, while no voids are located in Ni layers or along the Ni/Al interfaces. This is because the spall strength of single-crystalline Ni is higher than that of single-crystalline Al. We reveal influences of a shock-induced chemical reaction on dynamic spalling damage and fracture processes. An abnormal decrease -> increase -> decrease zigzag variation tendency of the spall strength of Ni/Al nanolaminates as the impact velocity increase is observed in our simulations, which resulted from combining effects of micro-structures, chemical reactions, and temperature softening. When the impacting intensity is relatively low, the spall strength of Ni/Al nanolaminates decreases as the impact velocity increases due to micro-structure effects. However, when the loading velocity increases to a certain magnitude (2.5 km/s), the intimate contact of liquid Al with amorphous Ni near the interface makes the chemical reaction rate increase rapidly to form a large amount of Ni/Al alloys and enhances the spall strength. Published under an exclusive license by AIP Publishing.

Automated summary

The spalling behaviors of Ni/Al nanolaminates are influenced by the combination effects of micro-structures, chemical reactions, and temperature softening. A zigzag variation trend of spall strength is observed with increasing impact velocity, which is attributed to the interaction of liquid Al with amorphous Ni near the interface leading to rapid chemical reactions and enhanced spall strength.