The surface of Ni_(61)Nb_(39) crystalline ingot was treated by laser surface melting with different processing parameters.A fully amorphous layer with a thickness of approximately 10μm could be produced on the top surface under optimal parameters.An amorphous-crystalline composite layer with the depth from 10 to 50μm,consisting of amorphous matrix and intermetallic phases of Ni_3 Nb and Ni_6Nb_7,could be formed.The micro-hardness(about 831HV)of the treated surface was remarkably improved by nearly 100% compared with the value of the crystalline substrate caused by the formation of the fully amorphous structure.A finite volume simulation was adopted to evaluate the temperature distribution in the laser-affected zone of Ni_(61)Nb_(39) alloys and to reveal the mechanism of glass formation in the laser-affected zone.
Surfaces of three types of CuZr-based bulk metallic glasses (BMGs) were modified by laser surface treatment (LST), and the influence of the treatment on structure and mechanical properties of these alloys was investigated. The phase structure of as-cast and laser-treated samples was characterized by XRD and the morphology of the alloys after fracture was examined by SEM. The compressive plasticity of treated Cu47.5Zr47.5Al5 and Cu46.5Zr47.5Al5Co1 BMGs can be improved from 0.5% to 2.0% and from 1.2% to 5.7% respectively compared with the as-cast ones, while (Cu0.55Zr0.40Al0.05)99Er1 BMG shows insignificant change of plasticity. The improvement in plasticity is attributed to induced crystallization of B2 CuZr phase in the treated surface zone of selected metallic glasses.
WU GuoJuanLI RanLIU ZengQianCHEN BingQingZHANG Tao
