Research On Modification Of Ti_42.5Cu_42.5Ni₁₀Zr₅ Bulk Metallic Glass Composite-ceramic Rolling Deformation And Cryogenic Treatment

Titanium-based bulk metallic glass alloys have corrosion resistance ability, excellent physical properties, and mechanical properties, making it as a promising material in many application fields. The preparation and research of the Ti-based bulk metallic alloys and their composites with good overall performance have been the hot study topic in the amorphous material field. In this paper, Ti_42.5Cu_42.5Ni₁₀Zr₅ bulk metallic glass composite was prepared by a high vacuum melting copper mold suction casting equipment and was chosen as the research object. The effect of ceramic rolling and cryogenic treatment on mechanical properties, thermal properties and corrosion resistance ability of Ti_42.5Cu_42.5Ni₁₀Zr₅ bulk metallic glass composite were investigated, respectively.Prior plastic deformation processing, ceramic rolling, was utilized to tune mechanical properties of Ti_42.5Cu_42.5Ni₁₀Zr₅ bulk metallic glass composite in a large strain rate ?0.5-Is-1? conditions at room temperature. The structure of alloy was characterized by ?XRD? and the thermal properties were measured using DSC with the heating rate of 20 K/min. The Vickers hardness test device was used to measure the micro-hardness of as-cast and as-rolled samples. Compression tests were carried out using an Instron 3369 tensile testing machine with an initial strain rate of 2×104/s. The micro-structure, the shear bands and the fracture morphology of the samples were investigated by SEM. The metallic glass composite sample exhibits plastic deformation with 15%thickness reduction ratio through ceramic rolling at room temperature. The mechanical properties of the Ti-based BMG composite can be improved by cold rolling, which the compressive strength rises from 1720MPa to 1860MPa and the cold-rolled sample exhibits enhanced plasticity of 5.3% instead of no plastic deformation of the as-cast sample. The shear band was introduced into the bulk metallic glass composite specimen and the morphology of the shear bands in the cross section of the as-rolled specimens appeared stepped structure and the shear bands were parallel to each other. There were some secondary shear bands except the primary shear bands after ceramic rolling process. The thermodynamic parameters of the samples were measured by DSC before and after rolling, the crystallization enthalpy and the structural relaxation enthalpy of the sample were reduced after rolling process.Ti_42.5Cu_42.5Ni₁₀Zr₅ bulk metallic glass composite was processed by cryogenic treatment at different times. The variation of mechanical properties thermodynamics properties and corrosion resistance of the amorphous composite samples before and after the cryogenic treatment was studied. With the increase of the time of cryogenic treatment, the micro-hardness and the compression fracture strength of the specimen were both improved, especially at cryogenic 9 days, the hardness of 536Hv and the strength of 1960MPa reached to the maximum. But when the cryogenic time reached to 11 days, the rising tendency of the strength and hardness of the samples decreased and became flat. The crystallization temperature Tx and the glass transition temperature Tg of the samples after rolling shift to lower temperature with the increase of the time of cryogenic treatment. The relaxation enthalpy of composite specimen decreases with increasing cryogenic time. The effect of cryogenic treatment on the mechanical properties of the bulk metallic glass composite specimen is the result of joint action of many factors. Cryogenic treatment increased the heterogeneity of microstructure in bulk metallic glass composite samples, leading to the deterioration of the corrosion resistance ability of the composite samples.