Ti-Cu基非晶合金玻璃形成能力与力学性能

Glass Forming Ability and Mechanical Properties of Ti-Cu-based Bulk Metallic Glasses

基于"二元共晶混合"法设计Ti-Cu-Ni-Zr合金成分,通过水冷铜模铸造法制备出不同直径Ti-Cu-Ni-Zr合金棒。利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、万能材料试验机和扫描电镜(SEM)研究了Ti-Cu-Ni-Zr合金玻璃形成能力和力学性能。结果表明,Ti-Cu-Ni-Zr合金具有较高玻璃形成能力,其临界直径可达4 mm;Ti-Cu-Ni-Zr合金玻璃形成能力近似相等,而表征玻璃形成能力的热力学参数过冷液相区ΔTx,参数γ,约化玻璃转变温度Trg也近似相等。Ti_(32.3)Cu_(47.6)Ni_(7.9)Zr_(12.2)和Ti_(31.6)Cu_(48.2)Ni_(7.7)Zr_(12.5)大块非晶合金分别具有0.7%和0.2%的塑性,而Ti_(30)Cu_(49.5)Ni_(7.2)Zr_(13.3)和Ti_(28.55)Cu_(50.7)Ni_(6.75)Zr_(14)大块非晶合金断裂机制近似为脆性断裂。Ti-Cu-Ni-Zr大块非晶合金塑性越大,其剪切带数量越多且扩展深度越大,反之亦然。另外,对于塑性材料,锯齿流变振幅越大,对应样品表面剪切带扩展深度越明显;锯齿流变振幅越小,对应样品表面剪切带扩展深度越浅;近似脆性材料的锯齿流变对应次剪切带萌生,而对于完全脆性大块非晶合金,在应力-应变曲线上并未发现锯齿流变现象,相应的在样品外表面也并未发现次剪切带。

The composition of the Ti-Cu-Ni-Zr bulk metallic glasses（BMGs） was designed based on ＂binary eutectic mixture＂ method. The Ti-Cu-Ni-Zr alloy rods with different diameters were prepared by water-cooled copper mold casting. The thermodynamic parameters were tested and the mechanical properties were investigated by differential scanning calorimeter（DSC）, X-ray diffraction（XRD）, universal testing machine and scanning electron microscope（SEM）. The results show that the Ti-Cu-Ni-Zr BMGs have the high glass forming ability, and the critical diameter can reach 4 mm. The glass forming ability of Ti-Cu-Ni-Zr BMGs are approximately equal, and the thermodynamic parameters of characterizing glass formation ability, such as supercooled liquid region（35）Tx, g parameter, reduced glass transition temperature Trg, are also approximately equal. The Ti32.3Cu47.6Ni7.9Zr12.2 and Ti31.6Cu48.2Ni7.7Zr12.5 BMGs have the plasticity of 0.7% and 0.2%; however, the fracture mechanisms of Ti30Cu49.5Ni7.2Zr13.3 and Ti28.55Cu50.7Ni6.75Zr14 BMGs are the similar brittle fracture. For the Ti-Cu-Ni-Zr BMGs, the greater the plastic deformation is, the more the number of the shear bands are, the greater the depth are, and vice versa. In addition, for the plastic materials, the large the amplitude of the serrated flow is, the deeper the surface shear bands are, and vice versa. For the approximate brittle materials, the serrated flow corresponds to the initiation of the second shear band; and for the completely brittle materials, the phenomenon of serrated flow is not found in the stress-strain curves; however, the second shear bands are not found on the surface of the sample.