【作者】 孙春静；

【导师】 耿浩然；

【作者基本信息】 山东大学 ， 材料加工工程， 2007， 博士

【摘要】 液态金属微观结构的变化将引起熔体敏感物性发生变化,根据熔体的敏感物性变化规律可以揭示其结构变化特征,为合理控制传递熔体结构信息的遗传因子提供科学依据。物性作为熔体结构的宏观表征易于测量和评价,并赋有特殊的物理意义。金属熔体结构及其物理性质的研究在凝聚态物理以及材料科学的应用领域都具有十分重要的意义。本文采用高温熔体物性测量仪,回转振动式黏度计、同轴圆筒流变仪及液态X射线衍射仪等方法研究了Sb、Bi及合金熔体的密度,In、Sn及合金熔体的黏滞性及Sb、Bi、Pb、Sn熔体的流变行为,揭示了熔体物理性能随温度等外界因素的变化规律,探讨了熔体结构的演变机理。采用改进的阿基米德方法系统地测试了Sb、Bi及其合金熔体的密度随温度的变化关系。实验结果显示,Sb熔体密度随温度升高成线性变化趋势,与他人文献结果一致。Bi熔体的密度随温度的升高先增大,在熔点以上约39K（310℃左右）时出现最大值:9.9895g/cm³,随后密度随温度线性减小。与他人文献比较发现,高温区本文的数据与他人结果吻合的较好,然而在熔点附近出现明显的偏离。Sb-Bi合金熔体密度的试验结果表明,合金熔体的高温区密度随温度基本成线性变化,且随Bi百分含量的增加密度增大。值得注意的是合金熔体密度在液相线温度以上大约30～50K的温度范围内出现了类似Bi熔体密度的异常变化。以Sb-Bi合金体系熔体密度的最大值连线在合金液相区绘图,可将原来空白的液相区粗略地分为两部分:结构密实区和结构疏松区。In、Sn及其合金熔体黏度与温度的变化关系显示,纯金属及合金熔体的黏度具有一个共同的特点——在整个测试温度区间内随温度升高基本上成Arrhenius指数趋势,不同的是黏度曲线不是连续变化的。In熔体的黏度在450～600℃温度范围内明显偏离拟合曲线,这与文献中原子配位数和相关半径的异常变化区间相对应。In熔体黏度的异常转变可能是因为在熔点以上的低温区液态In的结构类似面心立方晶格,随着温度升高转变为无规密堆结构所致。Sn熔体黏度的异常区间出现在400℃和810℃附近,DTA-TG差热分析表明在400℃和800℃出现热效应峰。In₈₀Sn₂₀熔体黏度的不连续变化分别在330℃和800℃附近,升温过程中的DSC在322℃和800℃出现明显的热效应峰。In₆₀Sn₄₀合金熔体黏度在200～250℃的温区内,熔体黏度发生陡降,高温区黏度随温度变化较平缓。In₆₀Sn₄₀合金熔体黏度-温度关系的异常变化区间与液态XRD的相关半径和原子团簇的原子数随温度变化的异常区间基本一致,表明合金熔体微观结构转变是导致黏度发生异常变化的本质原因。In₅₀Sn₅₀合金和In₃Sn₉₇合金熔体黏度的异常温区分别为350℃和750℃左右。通过对Arrhenius公式作对数变换,分别计算了Sn及In-Sn合金不同温区的流团体积和黏流激活能,发现熔体的流团体积和黏流激活能均随温度的升高而减小。将不同合金熔体的黏流激活能和流团体积进行比较,发现In₅₀Sn₅₀合金熔体的流团体积和黏流激活能比其他合金的大。利用前人的经验公式及本文所得的黏度数据,计算了试验条件下难以精确测得的液态金属重要物性参数,如液态金属的表面张力、熔体扩散系数。考察了水平永磁场对Sb、Bi及Sb-Bi合金熔体黏度的影响,结果表明,不同磁场条件下Sb、Bi及其合金熔体的黏度随温度成指数递减变化趋势。水平永磁场对金属熔体黏度的影响非常明显,相同温度下的黏度随磁场强度的增加而增大。磁场对熔体黏度的影响是通过熔体中带电粒子作切割磁力线运动时产生洛仑兹力所致。就金属Sb、Bi而言,磁场对Sb熔体的作用更显著。磁场对合金熔体黏度的影响随着按Bi₈₀Sb₂₀、Bi₆₀Sb₄₀、Bi₄₀Sb₆₀、Bi₂₀Sb₈₀的顺序依次增大。建立了磁场条件下黏度随温度变化关系的数学模型。运用同轴圆筒流变仪研究了Pb、Sb、Bi、Sn金属熔体的流变特性。以牛顿定律为理论依据进行推导,将牛顿流体的判别依据——试验中难以精确测得剪切应力和剪切速率的关系,简化为容易获取的扭矩和转速的关系。结果显示,Pb、Sb熔体在所测的范围内扭矩与转速成良好的线性关系,表明熔体为牛顿流体。而Bi、Sn的扭矩与转速关系在低温区和较高的转速条件下明显偏离线性,表现出一定的非牛顿特性。探索了Sb₂₀Bi₈₀和Sb₈₀Bi₂₀合金熔体的流变性,发现Sb₂₀Bi₈₀熔体具有类似Bi的特征,即在温度较低和转速较高时表现出一定的非牛顿特性;而Sb₈₀Bi₂₀的扭矩与转速在整个测定范围成良好的线性关系。占据合金主要成分的Bi、Sb在Sb₂₀Bi₈₀和Sb₈₀Bi₂₀合金熔体的流变性起了关键性作用。同时探讨了Pb₇₀Sn₃₀、Pb_38.1Sn_61.9、Pb₂₀Sn₈₀合金熔体的流变性,发现Pb_38.1Sn_61.9合金熔体的扭矩与转速关系成较好的线性关系,数值比较稳定。亚共晶及过共晶熔体的扭矩与转速的关系稳定性较差。不同合金熔体的流变特性与其液态结构演变有密切联系。这种现象可能是由于Pb-Sn合金组织中的富Pb和富Sn相在熔化后较大范围内并未完全均匀熔合,尚存在Pb-Pb和Sn-Sn局域同类原子集团。随着温度升高,富Pb和富Sn集团发生重组造成的。以Bi、Sn熔体流变的试验结果为基础,结合理论分析,建立了剪切作用下金属熔体微观结构流变模型。更多还原

【Abstract】 The micro-structural change of liquid metal can induce the variation of physical properties. The variation of physical properties can indicate the feature of melt micro-structure, which would provide much scientific theory for the controlling of the heredity of melt structure. The physical properties of melt, with special physical meaning, can be easily measured and evaluated. It is of significance to investigate the micro-structure and physical properties of melt both for the physics of condensed matter and for the application of material science.In this paper, the densities of Sb, Bi and Sb-Bi alloy melts, the viscosities of In, Sn and In-Sn alloy melts, the rheological properties of Sb, Bi, Pb, Sn melts have been investigated by employing the physical properties measuring instrument, torsional oscillation viscometer for high-temperature melt, coaxial cylinder viscometer and X-ray diffractometer. The dependences of physical properties on the temperature and other external conditions have been posted. The evolution mechanisms of micro-structure have been discussed.The densities of Sb, Bi and Sb-Bi alloy have been measured systematically at different temperatures using the improved Archimedean method. The results show that the density of Sb melt decreases linearly with the increasing temperature, which is in a good agreement with other literatures. The density values of Bi melt increase as the temperature increases, getting to the maximum:9.9895g/cm³ at the temperature 39°C above the melting point, and then decrease linearly. Compared with others’ results, the density of Bi melt is well consistent with the references at high temperature, but there is a distinct abnormal change near the melting point. The densities of Sb-Bi alloys decrease linearly with the increasing temperature and increase with the content percent of Bi. There are abnormal phenomena resembling that of Bi melt at the temperature 30～50K above the liquidus temperature.There is a common characteristic for the viscosities of In, Sn and In-Sn alloy melts that the temperature dependence of these melts follows the Arrhenius formula on the whole. It is different that the viscosity curves change discontinuously. For example, the viscosity of In melt deviates from the fitting curve at the range of 450～600℃, which is in accordance with that of coordination number and correlation radius in the reference. It is considered that the abnormal change of In melt is possibly due to the transition from resembling face centered cubic lattice at low temperature to random close-packed structure at high temperature. The abnormal regions of the viscosity of Sn melt are at 400℃and 810℃, respectively. The DTA-TG result in the reference also shows that there are two thermal peaks at 400℃and 800℃. The abnormal regions of the viscosity for In₈₀Sn₂₀ melt are at about 330℃and 800℃. There are two thermal peaks at 322℃and 800℃in the DSC curve. The viscosity of In₆₀Sn₄₀ melt is distinctly different, decreasing sharply within the scope of 200～250℃. There is a distinct abnormal change for In₆₀Sn₄₀ melt in the temperature dependence of the correlation radius and atomic number of the cluster. The abnormal regions of the viscosity for In₅₀Sn₅₀ and In₃Sn₉₇ melts are at about 350℃and 750℃, respectively. With the logarithmic transformation of the Arrhenius formula, the flow volumes and activation energies of Sn and In-Sn alloys at every temperature zone are calculated. The results show that the flow volumes and activation energies decrease with the increasing temperature. It is noticeable that the flow volumes and activation energies of In₅₀Sn₅₀ melt are larger than those of other melts.In terms of the empirical formulas, surface tension and diffusion coefficient of melt can be calculated accurately from the viscosity measured in this paper.The effect of horizontal permanent magnetic field on the viscosities of Sb, Bi and Sb-Bi alloy has been investigated. It is shown that the viscosities decrease exponentially as the temperature increases and increase with enhancing magnetic intensity. The influence of magnetic field on the viscosities is from the Lorentz force of electrification particle cutting the magnetic line. Compared with the Bi melt, the effect of the magnetic field on the Sb melt is more obvious. The effect of magnetic field on the viscosities of Sb-Bi alloy increases by degrees: Bi₈₀Sb₂₀, Bi₆₀Sb₄₀, Bi₄₀Sb₆₀, Bi₂₀Sb₈₀. A mathematic model with viscosity, temperature and magnetic intensity is put forward. The rheological features of Pb, Sb, Bi and Sn melt have been investigated. According to Newton law, the judgemental criterion of Newtonian fluid is transited from the relationship between shear stress and shear speed to that of torsion and rotate speed. It is shown that the relationships between torsion and rotate speed of Pb, Sb melt are linear, indicating that the melts are Newtonian fluid. But those of Bi, Sn melts deviate from the linear relation obviously at low temperature and high rotate speed, showing Non-Newtonian characteristic. The rheological feature of Sb₂₀Bi₈₀ melt has the same character with that of Bi melt, and Sb₈₀Bi₂₀ melt with the similar feature of Sb melt. It is concluded that Bi and Sb play an important role in Sb₂₀Bi₈₀ and Sb₈₀Bi₂₀ melts.In addition, the rheological features of Pb₇₀Sn₃₀, Pb_38.1Sn_61.9, Pb₂₀Sn₈₀ melts have been explored with the same method. It is indicated that the relationship between torque and rotate speed of Pb_38.1Sn_61.9 melt is linear and the values are stable, but those of Pb₇₀Sn₃₀ and Pb₂₀Sn₈₀ melt show small fluctuations. The rheological feature of melts is related with the evolution of melt micro-structure. It is considered that there are some riched-Pb and riched-Sn clusters in the melt when Pb-Sn alloys melt. The clusters rearranges with the increasing temperature.Based on the experiment results of Bi, Sn melts and in terms of theoretical analysis, a rheological model of melt micro-structure is established.更多还原