【作者】 胡建华；

【导师】 施雨湘；

【作者基本信息】 武汉理工大学 ， 载运工具运用工程， 2003， 博士

【摘要】 Ni／Al系和Ti／Al系金属间化合物是极有潜力的新一代高温结构材料，它们具有许多优良性能，如高温高强度、高温耐蚀性、高的比强度和比刚度等。但是从文献检索来看，其切削加工性和成形性能很差，目前对Ni／Al系金属间化合物的SHS合成研究主要存在着制作的Ni／Al系金属间化合物致密化程度较低、对反应特征没有详尽的描述、反应产物的形状尺寸精度较差、难以制备实用化制品等问题。 本文在国家自然科学基金、湖北省“十五”重点攻关计划等基金支持下，系统地论述了作者在Ni／Al系和Ti／Al系金属间化合物合成与成形的电脉冲效应方面研究成果。论文的主要内容与创新如下： 分析了Ni／Al、Ti／Al系金属间化合物室温塑性低的组织结构原因。提出了通过细化晶粒来提高室温塑性的措施，指出了细化晶粒的关键是在合成过程中使坯料处在高温状态的时间短，以抑制晶粒的长大过程。 研究了Ti／Al，Ni／Al系金属微粉的MM制备与活化方法，分析了MM处理工艺使金属粉末在物理性能、化学性能和组织结构等方面的变化。提出了描述纯金属粉末球磨时粉碎规律的算法，并对Ni、Fe等纯金属粉末球磨时的细化过程进行了计算。研究了不同的MM工艺参数对Ni粉、Al粉、Ti粉、Ni／Al粉和Ti／Al粉等材料的影响。 研究了在较低的脉冲电流作用下Ni／Al和Ti／Al的合成工艺过程与特点。采用合理的球磨工艺使合成反应产物的组织和显微硬度均匀化。提出了冷态下的脉冲电流处理可破碎粉粒表面的氧化皮，改善坯料的反应条件。分析了脉冲数量、脉冲时间、坯料高度、加压等参数对升温速度、T_ig和T_max、脉冲敏感性、反应产物致密性的影响。 对高密度脉冲电流下Ni／Al、Ti／Al的反应特点进行了分析，总结了在不同的充电电压、充电电容、脉冲电流、脉冲数量、脉冲持续时间等参数下，反应产物的组织与结构特点。计算了试样输入能量。研究发现短时高密度脉武汉理工大学博士学位论文冲作用下反应主要集中于边界，边界反应区的成分呈梯度分布。 分析和计算了Ni/AI、Ti/Al系金属间化合物的热力学参数。计算了坯料在高密度脉冲电流作用下粉坯的宏观温升。提出了坯料在高密度脉冲电流作用下粉坯微观温升的计算方法。建立了粉粒反应的缩球模型，推导了颗粒反应转换率随时间的变化规律，提出了颗粒反应转换率取决于界面化学反应速率和已反应层内的扩散速率两个因素并与反应进程有关。 分析了坯料的扩散过程，探讨了高密度电脉冲对扩散过程的影响。在高密度电脉冲作用下，表面扩散起主导作用。提出了在高密度电脉冲作用下，试样两端电场引起的扩散驱动力远大于浓度梯度引起的扩散驱动力。 计算了脉冲电流作用下，坯料内部各点的磁压强。分析了粉末材料的变形特点，并从塑性力学角度计算了粉坯在致密化变形过程中在几种不同应力状态下的变形和致密化规律，论述了电脉冲在致密化成形中的主要作用。更多还原

【Abstract】 Being a new generation of high temperature structure materials, Ni/Al and Ti/Al system intermetallic compounds are most potentially. They possess many excellent capabilities at high temperature such as high strength, corrosion resistance, contrast intensity and contrast rigidity. But a lot of information show that their properties of cutting and deformation are very dissatisfactory. At present there are some problems in SHS researches of Ni/Al and Ti/Al system intermetallic compound such as lack of detail description of reaction characters, low density of SHS products, dissatisfactory in precision of shapes and sizes, difficult in practical manufacture.Subsidized by the National Natural Science Foundation of China, "Tenth Five-year" Plan of Hubei province and so on, this dissertation systematically discussed the author’s researches on synthesis and deformation of Ni/Al and Ti/Al system intermetallic compound. The major contents and innovation of the research are listed as following:The organization and structure reasons of low plasticity of Ni/Al and Ti/Al system intermetallic compound at room temperature are analyzed. The measure of grains’ comminution is brought forward to improve plasticity at room temperature. The key of micro-crystal’s production is that the time of sample’s being at high temperature is shorter. The process of crystal’s growing up will be restrained.The preparation and activation methods of machine milling (MM for short) for Ni/Al and Ti/Al system tiny powder are researched. The technical treatment of MM makes metal powder a lot of changes in mechanical properties, chemical properties and organization structure. An arithmetic solution of comminution rule for pure metal powder in MM is put forward and then used to calculate the processes of pure metal powder such as Ni and Fe in MM. The effects ofdifferent MM parameters to different materials such as Ni powder, Al powder, Ti powder, Ni/Al powder, and Ti/Al powder are researched.The processes and characters of synthesis reaction for Ni/Al and Ti/Al under the influence of lower pulsating electric current are researched. Reasonable technology of MM will make the organization and micro-hardness of synthesis products more uniformity. The treatment of pulsating electric current at room temperature can break up oxidation surface of grains and improve the conditions of reaction. The effects of pulsating amounts, pulsating time, height of sample, pressure to rising speed of temperature, Tig and Tmax, pulsating sensitivity, and density of products are analyzed.The processes and characters of synthesis reaction for Ni/Al and Ti/Al under the influence of high intensity of pulsating electric current are researched. The characters of organization and structure of products under different parameters such as charge voltage, charge capacitance, pulsating electric current, pulsating amounts and pulsating duration are summarized. The input energy of sample is calculated. Some discovers are made in research. The reactions are concentrated in interface and the components of reaction areas are grads distributed.Thermodynamics parameters of Ni/Al and Ti/Al system intermetallic compound are analyzed and calculated. The macro temperature rising velocity of powder sample under the influence of high intensity of pulsating electric current are calculated. An arithmetic solution of micro temperature rising velocity of powder sample under the influence of high intensity of pulsating electric current are brought forward. Upon the foundation of contracted-ball, function equations of conversion rates of grains and time are deduced. It is brought forward that the conversion rates of grains rely on reaction velocity at interface and diffusion velocity in reacted layer and at the same time relate to reaction process.The diffusion processes of samples are analyzed. The effects of high intensity of pulsating electric current are discussed. It is found that the interfacediffusions are dominant under the influence of high intensity of pulsati更多还原