| 其他摘要 | According to criterions of Inoue’s rules, e/a ratio and Ra, and minor alloying, Zr- and Fe- based BMGs with good GFA, thermal stability and mechanical properties were successfully designed and synthesized. The results show that the alloys which have compositions close to eutectic composition have good thermal properties, while worse mechanical properties than that of alloys with a eutectic compositions. The maximum size and DTx are 5mm, 7 mm and 130K, 70K for Zr-, Fe-based alloys respectively. Al/Ni ratio strongly affect the crystallization behavior and properties of Zr-based alloys.
For Zr-based alloys, the maximum activation energy of crystallization is about 400 kJ/mol. The phases identified in annealed samples mainly are NiZr2,CuZr2 and Cu10Zr7, there is little change after different elements addition. The maximum compressive fracture stress reaches 1988 MPa for Zr64.5Ni15.5Al11.5Cu8.5. The addition of V, Y, Ti and Nb has beneficial effect on mechanical properties of Zr-based alloys. The nanohardness, elastic modulus, H/E ratio, elastic recovery limits and percentage of elastic recovery %R ranges in between 5.3-11.3 GPa and 84-131 GPa, 0.05-0.09, 0.6-0.78 and 22-40 respectively. Heat treatment strongly affects the mechanical properties such as Vicker’s hardness and nanohardness of Zr based BMGs.
For Fe-based alloys, DSC results reveal double stage crystallization reaction. The maximum activation energy of crystallization is about 606 kJ/mol for Fe60Zr10B15Co7Mo5.5Y2Si0.5 alloy. phases like Cr23C6、γ-Fe andη-Fe3Mo3C etc were identified in heat-treated samples. The maximum Vicker’s hardness of Fe-based alloy reaches 1548 MPa for Fe50Cr14Mo14C14B6Gd2. Fe50Cr14Mo14C14B6Dy2 alloy also had superior mechanical properties. The nanohardness, elastic modulus, H/E ratio, elastic recovery limits and percentage of elastic recovery %R ranges in between 14.9-22.3 GPa and 240-337 GPa, 0.062-0.067, 0.67-0.73 and 28-33 respectively. The Vicker’s hardness and nanohardness increase as the annealing temperature increase.
Ion irradiation of Zr55Cu30Al10Ni5 alloy up to 1h resulted in an increase of 43 % in nanohardness and 25 % of elastic modulus. Electron beam melting successfully produce composite containing nanocrystalline phase on the surface of the Zr55Cu30Al10Ni5 alloy. Crystalline phases are NiZr2, CuZr2 and Cu10Zr7. Microhardness of the sample having fine crystalline phases is higher than that of the samples having coarse crystalline phases.
The branching and intersected shear bands responsible for improvement of alloy’s ductility. The veins patterns, high density of liquid droplets, localized melting formed on the fracture surface of compressive sample, which is consistent with the adiabatic heating theory. |
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