Glass Forming Ability, Atomic Structure And Mechanical Property Of Zr-based Metallic Glasses

Metallic glass (MG), as a relative new member of materials family, has been focused widely by Scientific research personnel due to its unique structure and excellent properties. Up to now, glass forming ability and plastic property are the two main problem inhibit its industrial application. Therefore, we performed a systematic research about Zr-based metallic glass Zr-(Cu-Ag)-(Ni-Co)-Al-Be and Zr-Ti-Ni alloys aimed at the upper two questions. The following are our mainly achieved results:1) The glass forming ability of (Zr46(Cu4.5/5.5Ag1/5.5)46-y(Ni1/2Co1/2)yAl8)100-xBex (x=0-10at.%and y=2to6at.%) bulk metallic glasses (BMGs) were significantly improved by Be addition and substitution (Ni/Co) for (Cu/Ag).The biggest GFA in this series was found When x=7at.%, y=4at.%, with large supercooled liquid region△Tx=105K,Trg=0.643and γ=0.449. By discussing from the liquid properties and thermodynamic aspect, we found out that the strong GFA obtained is mainly due to the denser atomic packing and relatively low difference in Gibbs free energy for crystallization.2) Atomic structure and mechanical properties of Zr65TixNi35-x (x=0,5and10at.%) metallic glasses (MGs) are studied by using x-ray diffraction, x-ray absorption fine structure and nanoindentation techniques. It is demonstrated that Ti addition favors the formation of icosahedron-like clusters, making the environment around Zr and Ni atoms nearly12-coordinated and more shell-ordered, however deteriorates the plasticity of MGs. Accordingly, the shear transformation zone (STZ) volume becomes smaller. The results indicate that high plastic MGs would have low icosahedral short-range order and large STZ volume.