Influences of ion implantation on non-isothermal crystallization behaviors of bulk metallic glass

A plate-like Zr-based bulk metallic glass (BMG) was prepared by using a copper mold suction casting and an X-ray diffractometer (XRD) was utilized to determine its structure. Co ion implantation was carried out in a MEVVA source system. The influences of Co ion implantation on thermal stabilities and non-isothermal crystallization behaviors of the BMG were studied via a differential scanning calorimeter (DSC). The results show that Co ion implantation lowered the BMG's glass transition and crystallization onset temperatures, meanwhile, enhanced its super-cooled liquid regions. After Co ion implantation, crystallization behavior of the BMG changed from a single-stage precipitation process to a two-stage crystallization precipitation process. The apparent activation energies for glass transition and crystallization were enhanced. The crystallization process of the as-implanted specimen was relatively laggard compared to that of the as-cast one. The crystallization of the latter was typical nucleation and growth mechanism, while that of the former was interaction of annihilation of the free volumes, reduction of voids, short-range rearrangement caused by high energy implanted Co ions, various unknown complicated energy deliveries as well as nucleation and growth of crystalline grains. (C) 2009 Elsevier B.V. All rights reserved.