Ce_(70)Ga_(8.5)Cu_(18.5)Ni_3块体非晶合金的室温压缩塑性的显著尺寸效应

Strong Size Effect of Compressive Plasticity of Ce_(70)Ga_(8.5)Cu_(18.5)Ni_3 Bulk Metallic Glass at Room Temperature

以新开发的Ce70Ga8.5Cu18.5Ni3块体非晶合金为研究对象,系统研究了试样尺寸对其室温下压缩力学性能的影响。不同直径的非晶合金采用铜模吸铸法获得,采用万能试验机测量不同尺寸样品的室温压缩力学性能,并用扫描电子显微镜观察断裂后样品的端口形貌,此外,还通过差示扫描量热法分析不同样品的热力学性质。结果显示,直径1.5mm非晶柱状样品具有1%的压缩塑性,并伴随有典型的锯齿流变现象。随着非晶柱状样品尺寸的增加,其塑性逐渐消失。断裂后的样品的端口形貌呈现出典型韧窝状形貌,并且韧窝的密度随着样品尺寸的增加而降低。热分析结果表明,不同尺寸的铸态样品的玻璃转变之前都有一个明显的焓回复过程,而且其焓回复放热量和样品尺寸有近似的反比关系。尺寸较小的非晶合金在制备过程中拥有更快的冷却速率,能够保留更多的自由体积,为剪切带形核提供更多的形核点,表现出较好的宏观塑性变形能力。

In this work, the effect of sample size on the plastic deformation capacity in compresston at room temperature have been systematically investigated based on the CeT0 Gas. 5 Cu18. 5 Nia 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 mircroseope （SEM）, and the thermody- namic properties were analyzed by differential scanning calorimeter （DSC）. The as-casted φ1.5 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.