| Summary: | 碩士 === 義守大學 === 材料科學與工程學系碩士班 === 97 === In recent years, The Zr-Cu-Al-Ag alloy system is expected to have higher GFA and higher stabilization of supercooled liquid. Jang et al. has reported that adding silicon could effectively increase the activation energy of crystallization as well as increasing the incubation time for the Zr-base amorphous alloys. Therefore, the high GFA (glass forming ability) Cu42Zr42Al8Ag8 amorphous alloy is selected as the base alloy to investigate the effect of microalloying with Si. The (Cu42Zr42Al8Ag8)100-xSix amorphous alloy rods, x =0 to 1, with 2~4 mm in diameter were prepared by Cu-mold drop casting method. The glass forming ability, thermal properties and microstructure evolution was studied by differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). The XRD result reveals that these as-quenched (Cu42Zr42Al8Ag8)100-xSix alloy rods exhibit a broaden diffraction pattern of amorphous phase. The crystallization temperature and GFA (glass forming ability) of (Cu42Zr42Al8Ag8)100-xSix alloys increase with the silicon additions. In addition, both of the activation energy of crystallization and the incubation time of isothermal annealing for these (Cu42Zr42Al8Ag8)100-xSix alloys indicates that the (Cu42Zr42Al8Ag8)99.25Si0.75 alloy posses the best thermal stability among the (Cu42Zr42Al8Ag8)100-xSix alloy system. The Cu42Zr42Al8Ag8 alloy promoted the hardness with increasing Si content. the compression fracture strength and plastic strain can be reached about 2000 MPa and 3 % for the 1 at%Si and 0.5 at% amorphous alloy. Fracture occurs along the maximum shear stress plane, which is inclined at 45° to the direction of compressive loading，it have max stress for shear stress. Many shear bands can be observed on the side surfaces near the fracture area for the good plasticity.
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