Study On The Mechanical Properties Of Ce-Ga-Cu-Ni Amorphous Alloys And The Impact Of The Ce Purity On Glass Forming Ability In Ce-Ga-Cu Bulk Metallic Glasses

The impact of the purity of raw material Ce on glass forming ability is systematically studied through preparing the Ce7oGaxCu70-x (4<x<15) glassy alloys using different Ce raw materials with different purity. The results indicate that the GFA of the alloys is very sensitive to the Ce purity change and the critical size of the glassy sample would significantly change from 1 mm to 6-10 mm as the Ce purity changes by about 0.1% for the same alloy composition. Also, the correlation between the Ga content x and the critical diameter of the as-cast glassy rods changes obviously for different Ce bearing Ce7oGaxCu7o-x (4<x<15) alloys. Different from the results reported in other alloy systems like Fe-and Zr-based alloys, the GFA of the Ce-Ga-Cu alloys could be enhanced by using the low purity Ce raw material. The relationship between GFA and thermodynamic parameters is analyzed and found that there is a good correlation between the crystallization temperature and the glass-forming ability of these alloys and the better glass formers have higher the crystallization temperatures, which suggests that the GFA of Ce-based alloys closely related to the resistance ability of the supercooled liquid against crystalline. Furthermore, the impact of impurity elements of raw material Ce on GFA is investigated through annealing and crystallization experiments and the result indicates that low purity Ce raw materials can appreciably improve the formability of the present Ce-based bulk metallic glasses by suppressing the precipitation of Ce and CeCuGa3 phase due to the occurrence of phase competition. In general, the results indicate that the impurity of Ce base element substantially influences the stability of the Ce-based glass forming liquid, crystallization behaviors and thus GFA of the Ce-based glasses. Hence, the present work could help further understanding the effect of minor element addition on glass formation and its underlying mechanism in metallic glasses.In this work, the effect of sample size on the plastic deformation capacity in compression at room temperature have been systematically investigated based on the Ce70Ga8.5Cu18.5N13 bulk metallic glass which has been newly developed. Glassy rods with different diameters were prepared by a conventional copper mold casting method. The mechanical properties of different samples at room temperature were measured by universal testing machine, the fracture surfaces on the deformed samples were observed by scanning electron mircroscope (SEM), and the thermodynamic properties were analyzed by differential scanning calorimeter (DSC). The as-casted 01.5 mm sample exhibits plastic strain of about 1%, and serrations can be recognized from the compressive stress-strain curve. The plasticity increases with the decreasing diameter of the samples. The SEM images of the facture surfaces on the deformed samples reveal typical veinlike patterns, and the density of veinlike patterns increases with the decreasing diameter of the samples. The DSC curves of as-casted samples with different diameters exhibit one typical process of enthalpy reply, and the heat of relaxation and the sample size have similar inverse relationship. The results show that the smaller size samples have better macroscopic plastic deformation capacity, due to more free volume obtained from the faster cooling rate process of casting which provides more nucleation points for shear bands nucleation.