The interaction between local melting and helium bubble in radiated aluminium under dynamic tension at high temperature and strain rates

Abstract

Materials exposed to extreme radiation environments (e.g., nuclear devices) accumulate substantial defects, such as helium (He) bubbles. These defects can alter material properties, including melting behavior, which has not been intensively explored. Here, the melting process and the He bubble evolution in aluminium under dynamic tension at high temperature and strain rates were investigated via molecular dynamic simulations. We found that the melting process contains slow premelting and sequential fast local melting at relatively lower strain rates (10⁶ ∼ 10⁸ /s). The rapid growth of the bubble promotes local melting, which in turn facilitates the migration and shrinkage of the bubble. The underlying microscopic mechanisms for the interplay between the bubble and local melting have also been uncovered. Such interaction becomes weak at high strain rates (10⁹ ∼ 10¹⁰ /s). Homogeneous melting occurs directly and spontaneously throughout the sample, and local melting around the bubble becomes inconspicuous. The evolution process of the bubble gets simple, characterized by continuous growth without shrinkage or migration. Furthermore, damage development is dominated by the growth of the He bubble, which occurs after the sample is nearly completely melted at lower strain rates while it happens concurrently with melting at high strain rates.