Effects Of Ion Irradiation On Cu-Zr Based Metallic Glasses

In this dissertation,Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys were selected as the model materials.The irradiation tests have been carried out under 120 ke V hydrogen ion,helium ion and nitrogen ion with total fluencies of 1.7×10¹⁵ions/cm²,5×10¹⁵ions/cm²,1×10¹⁶ions/cm² and 2×10¹⁶ions/cm².The microstructure and related properties of as-spun and irradiated samples have been examined by high energy synchrotron X-ray diffraction,nano-identation,scanning electron microscope and atomic force microscope,etc.,and the effects of ion irradiation on CuZr-based amorphous alloys have been summarized.The collisions between the incident ions and the target atoms were calculated carefully.The calculation results show that,compared with hydrogen ion and helium ion,nitrogen ion in amorphous alloys exhibits the fastest energy loss rate and the shortest incident range whereas hydrogen ion in amorphous alloys possesses the slowest energy loss rate and the longest incident range.The structural evolution of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys have been investigated before and after ion irradiation.It shows that the hydrogen ion,helium ion and nitrogen ion irradiation can't induce any crystallization of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys.Low-dose ion irradiation will produce irradiation damages such as vacancies and shifted atoms in the amorphous matrix,causing the expansion of the atomic bond of the amorphous alloy,and thus loosening the structure of the amorphous alloy.Contrarily at a high irradiation dose,the atomic self-diffusion movement ability of the amorphous alloy is enhanced,and the structure of the amorphous alloy changes to more ordered and tighter structure with a low energy state.Irradiation of hydrogen,helium and nitrogen ions induces structural changes of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys,which in turn affects the surface morphology,mechanical,physical and chemical properties.It is found that after ion irradiation,the sample surface of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys demonstrate no obvious irradiation damages.A low irradiation dose causes an increase in the surface roughness of the amorphous alloys whereas a high ion irradiation dose reduces its roughness due to the plastic flow of surface induced by ion irradiation.Microstructure of the amorphous alloys induced by ion irradiation tends to be tight,and their mechanical properties are improved.Under nitrogen ions irradiation with total fluencies of 2×10¹⁶ions/cm²,the nanohardness of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloy is 8.91 GPa and 9.07 GPa,respectively.The electrical properties of the amorphous alloys have been studied.The electrical conductivity of the irradiated amorphous alloys can be affected by both the structure of amorphous alloys and the irradiated ions.The doping of the irradiated ions in the amorphous alloys hinders the movement of free electrons.In addition,the effects of ion irradiation on the corrosion resistance of Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys have been also studied.A low-dose ion irradiation generates irradiation defects in the amorphous alloys,which reduces the corrosion resistance of amorphous alloys.With increasing the irradiation dose,the structural stability of the amorphous alloys is enhanced and the corrosion resistance is increased.When the ion irradiation dose continues to increase,the uniformity in the composition and structure of the Cu₅₀Zr₅₀ and Cu₅₀Zr₄₅Al₅ amorphous alloys are destroyed,reducing the corrosion resistance.