| Bulk amorphous alloy is a new structural material, which possesses metallic bond and arrangement of atoms similar to inorganic glass atoms. Attribute to its excellent mechanical, physical and chemical properties, it has been widely used in military and the area of sophisticated micro-devices, etc. However, bulk amorphous alloy has two main problems: poor plasticity at room temperature and poor forming ability. In order to improve plastic property, this research take Ti32.8Zr30.2Be22.7Cu9Ni5.3( ZT3) bulk amorphous alloy as object, based on the free volume theory the research design a serious of completely amorphous alloys with large size and plastic. Then bulk metallic glass matrix composite(BMGMC) of β phase in-situ precipitation has been fabricated based on the pseudo ternary phase diagram. In order to improve the compatible deformation capability of Ti Zr-based BMGMC, the strength of dendrite is improved through solid solution strengthening, hot-pressing and other methods in this research. Firstly, to solve the problem of poor forming ability, the thermal mechanical properties and morphologies before and after deformation of Ti Zr-based BMGMC have been detected. Then the research take the classic Zr-based bulk amorphous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5(VitreloyTM1) as research object, test its casting fluidity, and verify it by fabricating relevant mathematical model. Simultaneously, gravity casting experiment are carried out by optimized parameters.As adding positive mixing enthalpy elements Nb and Fe into ZT3 matrix group, the research results indicate that content of free volume(FV) in(ZT30.9)Nb10 obviously increased through DSC detection, which leads to the maximum strength and plastic deformation increase to 2080 Pa and 8.3%, respectively. Through component tailoring, the maximum compression strength of Ti38.8Zr28.8Cu6.2Be16.2Nb10 BMGMC is up to 2150 MPa and the plastic deformation is up to 12%. The TEM analysis finds that serious lattice distortion, pile-ups of dislocation and partial shear rheological areas distribute in the interface. Then the research discusses the effect of cooling rate on the structure property of Ti Zr-based BMGMC. It finds that as the cooling rate decreases, the yield strength of the dendrite declines rapidly accompanied with obviously growth and reunion of the dendrite. The result indicates that the size and morphology of the dendrite in the Ti Zr-based BMGMC plays a crucial role on the overall performance.The composition of Ti38.8Zr28.8Cu6.2Be16.2Nb10 is adjusted through adding Al and O2 which are α-phase stable elements of titanium. As the content of Al is 6.2 at.%, the sample of Ti38.8Zr28.8Cu6.2Be16.2Nb3.8Al6.2 is amorphous again. Along with the increasing of Al content and proportion adjustment of titanium and zirconium, microstructure change obviously from the micro-dendrites to isometric crystal to columnar crystal at edge; what’s more, it change from micro-dendrites to large reunion isometric crystal at center. An α-Ti crystal phase precipitates from the glass matrix as the leakage casting diameter of Ti50.8Zr16.8Cu6.2Be6.8Al15.6Nb3.8 is 6mm. If oxygen is added in the form of Zr O2, obvious balling phenomenon occurs in precipitated phase, and the particles become significantly larger with the increase of Zr O2. As the addition amount of Zr O2 is 1.0 wt.%, the deformation pattern transforms from the second phase strengthening to matrix strengthening, and the maximum tensile strength increases from 1691 MPa to 1800 MPa.Optimizing the dendrites of Ti38.8Zr28.8Cu6.2Be16.2Nb10 through adding Ta which is a β-phase stable element of titanium, the result indicates that the hardness of the dendrites improves with the increase of the degree of solid solution strengthening, and the work hardening of Ta0.0–Ta8.0(Vol.%)is obvious during compressive progress. During tensile progress, the maximum strength of Ta0.5 is 1680 MPa, and the plastic deformation is 10.2%. It finds that the lattice distortion and dislocation density of the dendrite increases significantly while doing inverse Fourier transform for the high resolution images at the interface between amorphous and dendrite. After solid solution strengthening, dendrites can effectively prevent the expansion of the shear bands, and promote furcation and proliferation, then produce multiple shear bands. During the thermal mechanical properties test for Ta0.5 in Gleeble3500, the results indicate that its deformation is uniform deformation as the temperature is 315℃ and the strain rate is 0.001 /s. Therefore the hot-press molding is expected to become the ideal forming method for parts preparation.Through testing the casting fluidity of VitreloyTM1 amorphous alloy, it finds that the filling process is smoothly as the temperature from 850℃ to 950℃ and the pressure from 0.025 MPa to 0.030 MPa. Flow length increased monotonically with the increase of suction casting temperature and pressure, what’s more, it increases exponentially with the increase of runner diameter. The flow length equation of Zr-based bulk amorphous alloy, built according to the conservation law of heat transfer and Rayleigh rule of fluid mechanics, is consistent with the measured values. According to the research results, large size amorphous alloy bar and samples of outline clear Olympic icon are successfully prepared. |
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