【作者】 梁维中；

【导师】 沈军； 孙剑飞；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2006， 博士

【摘要】 本文以Ni基合金为研究对象,设计Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5（at.%）块体非晶合金成分,对其在过冷液相区内的晶化行为及在室温下的单轴压缩力学行为进行了系统研究。应用二元共晶比例混合法设计了Ni₄₁Ti_25.3Zr_25.3Al_8.4四元Ni基非晶合金成分,以钨极电弧炉熔炼、铜模铸造工艺制备出直径0.5 mm的非晶样品。通过金属元素Cu替换Ti方式进行成分优化,获得最大玻璃形成能力为直径1 mm的Ni₄₁Ti_20.3Zr_25.3Al_8.4Cu₅非晶合金。对Cu添加有益于提高Ni₄₁Ti_25.3-xZr_25.3Al_8.4Cu_x （x = 1, 3, 5, 6, at.%）合金系的玻璃形成能力进行了分析。在五元非晶合金的基础上进一步增加体系的混乱程度,采用类金属元素Si替换元素Zr,获得六元Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5非晶合金,其最大玻璃形成能力为直径4 mm的非晶样品。分析了Si元素添加有效地提高Ni₄₁Ti_20.3Zr_25.3-xAl_8.4Cu₅Si_x（x = 2.5, 3.5, 4.5, at.%）合金系玻璃形成能力的作用。对不同升温速率下Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5非晶合金的变温晶化行为研究表明:DSC热分析曲线展示单一晶化反应的放热峰;升温速率越高,晶化程度越弱,透射电镜图像中体现较少数量及较小尺寸的纳米晶粒。初始晶化激活能为379.339 kJ/mol,表明其具有较大的热稳定性。分析了变温晶化行为。在过冷液相区内的等温晶化行为分析表明:DSC热分析曲线仍然表现单一晶化反应的放热峰。在铸态合金中存在的球形析出物随着等温时间增加而逐渐消失,表示出亚稳相的特征,这表明合金的晶化是在非晶基体上形成纳米晶及从亚稳球形初生相分解的综合作用。研究了不同程度的非晶亚稳结构对Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5块体非晶合金压缩力学行为的影响。X-射线衍射、DSC热分析及扫描电镜（SEM）观察表明:直径为2 mm及3 mm的非晶合金样品呈现不同程度的微观非晶结构特征及断裂特征。2 mm非晶样品的单轴压缩应力-应变曲线呈现了2851 MPa的断裂强度及0.5%的塑性应变,而3 mm非晶样品的断裂强度为2724 MPa,塑性应变为零。2 mm及3 mm样品的断裂表面均由平滑的剪切区及凹凸不平的粗糙区组成,但两者的剪切断裂角不同,分别为43.8°和41.8°。对断裂表面形成的粗糙区进行了分析,并对粗糙区内存在的微型塑坑结构进行了解释。应用Argon提出的剪切转变模型分析了不同程度非晶结构诱导不同的塑性变形的更多还原

【Abstract】 In this dissertation, the composition of Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5 （at. %） bulk metallic glass （BMG） was designed in Ni-based alloys. The uniaxial compressive deformation and fracture behaviors at room temperature as well as crystallization behaviors in the supercooled liquid region of the Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5 BMG alloy were investigated.The chemical composition of Ni₄₁Ti_25.3Zr_25.3Al_8.4 amorphous alloy was designed by a method of proportionally mixing the deep-euectic compositions of relevant binary alloys. The amorphous alloy sample with a diameter of 0.5 mm was obtained by using the arc-melting copper mould casting method. The BMG alloy of Ni₄₁Ti_20.3Zr_25.3Al_8.4Cu₅ was acquired by the addition of Cu for Ti, achieving fully amorphous sample of 1mm in diameter. The beneficial effect of Cu on the GFA of Ni₄₁Ti_25.3-xZr_25.3Al_8.4Cu_x（x = 1, 3, 5, 6,at. %） alloy system was analyzed. By further increasing the confusion degree of the amorphous alloy system, Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5 BMG alloy was obtained by substituting Zr with metalloid Si, which can be synthesized into an amorphous sample with a diameter of 4 mm using copper mould casting. The role of Si addition to Ni₄₁Ti_20.3Zr_25.3-xAl_8.4Cu₅Si_x（x = 2.5, 3.5, 4.5,at. %） alloy system in enhancing GFA was also analyzed.By means of Differential scanning calorimeter （DSC）, the crystallization of Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5 BMG alloy under different continuous heating rates showed a single exothermic stage. The higher heating rate, the lower the crystallization degree would be. The primary crystallization activation energy is as high as 379.339 kJ/mol, which represents a larger thermal stability, and the continuous crystallization behavior of the studied BMG alloy was analyzed. The isothermal annealing crystallization DSC curve of the Ni₄₁Ti_20.3Zr_21.8Al_8.4Cu₅Si_3.5 BMG alloy in the supercooled liquid region still experienced a single exothermic stage. With the annealing time increasing, the disappearance of sphere-like crystalline phases in as-cast alloy confirmed its metastable nature. The crystallization of the studied alloy occurs via the precipitation of the nanocrystalline phase and the decomposition of the sphere-like primary phases.更多还原