Microstructure and properties analysis of accumulative-roll-bonding-processed Mg–Li/Ta composites for shielding of high-energy electron

Abstract

The rational combinations of low/high-density metallic materials have been proved to be effective in shielding high-energy electron radiation, however, little has been studied and reported about their synthesis, microstructure, properties and stability against irradiation. In present work, Mg–Li alloy and pure Ta sheets were used to prepare such a novel low/high-density shielding composite by accumulative roll bonding (ARB). Results showed that a uniformed microstructure of composite could be produced after four ARB cycles. Both ARB process and irradiation caused no obvious change in phase compositions of raw materials. In larger areal mass 8.2–12.3 g/cm2, the Mg–Li/Ta composite is a more efficient shield than pure Mg–Li and Ta. Treated by irradiation, a notable number of cavities accompanied by dislocations were formed as main defects in α-Mg phase. The induced dislocations facilitated the nucleation and growth of {1 0–1 2} twins, which in turn acted as sinks of defects. By contrast, Ta phase exhibited good radiation stability as no signs of visible cavities. During ARB process and irradiation, the textures of α-Mg and Ta in composite all varied distinctly. The average micro-hardness of Mg–Li and Ta phase increased with ARB cycles. Treated by irradiation, Mg–Li matrix was sharply hardened while hardness of Ta was slightly decreased. The tensile strength of Mg–Li/Ta composite increased in ARB process and reached the maximum after four cycles. After irradiation, composite exhibited same strength but severe loss of ductility.