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Processing and characterization of phase boundaries in ceramic and metallic materials.

机译：陶瓷和金属材料中相界的处理和表征。

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The goal of this dissertation work was to explore and describe advanced characterization of novel materials processing. These characterizations were carried out using scanning and transmission electron microscopy (SEM and TEM), and X-ray diffraction techniques. The materials studied included ceramics and metallic materials.; The first part of this dissertation focuses on the processing, and the resulting interfacial microstructure of ceramics joined using spin-on interlayers. SEM, TEM, and indentation tests were used to investigate the interfacial microstructural and mechanical property evolution of polycrystalline zirconia bonded to glass ceramic MaCor™, and polycrystalline alumina to single crystal alumina. Interlayer assisted specimens were joined using a thin amorphous silica interlayer. This interlayer was produced by spin coating an organic based silica bond material precursor and curing at 200°C, followed by joining in a microwave cavity or conventional electric furnace. Experimental results indicate that in the joining of the zirconia and MaCor™ no significant interfacial microstructural and mechanical property differences developed between materials joined either with or without interlayers, due to the glassy nature of MaCor™. The bond interface was non-planar, as a result of the strong wetting of MaCor™ and silica and dissolution of the zirconia. However, without the aid of a silica interlayer, sapphire and 98% polycrystalline alumina failed to join under the experimental conditions under this study. A variety of interfacial morphologies have been observed, including amorphous regions, fine crystalline alumina, and intimate contact between the sapphire and polycrystalline alumina. In addition, the evolution of the joining process from the initial sputter-cure to the final joining state and joining mechanisms were characterized.; The second part of this dissertation focused on the effects of working and heat treatment on microstructure, texture, phase boundary movement, and mechanical property evolution in Ti-6Al-4V wire. The as-received wire consisted of equilibrium a and metastable β phases and had a moderately strong fiber texture with prism plane normals aligned with the wire axis. The wire was worked by extrusion, solution heat-treatment and water quenching, and aging. The extrusion process strengthened the as-received texture. After solutionization and quenching, microstrucual observations showed the presence of many needlelike martensitic platelets in the prior β phase regions. Texture analysis revealed that a secondary fiber with basal plane normals aligned with the wire axis emerged at the expense of the initial texture, indicating that highly preferred phase boundary motion (variant selection) occurred during the β → α transformation. The strength of the variant selection consistently increased with solutionization temperature and time. In addition, the effects of dislocation type and density on variant selections were further investigated. This implies that strategic prior deformation and heat treatment can be exploited to design the resulting texture and microstructure and consequently optimize the properties of titanium products.
机译：本论文的目的是探索和描述新型材料加工的高级表征。这些特征是使用扫描和透射电子显微镜（SEM和TEM）以及X射线衍射技术进行的。研究的材料包括陶瓷和金属材料。本文的第一部分着重于加工过程，以及由此产生的使用旋涂中间层连接的陶瓷的界面微观结构。使用SEM，TEM和压痕测试研究了结合到玻璃陶瓷MaCor™上的多晶氧化锆和结合到单晶氧化铝上的多晶氧化铝的界面微观结构和力学性能演变。使用薄的无定形二氧化硅夹层将夹层辅助的样品连接起来。该中间层是通过旋涂有机基二氧化硅键合材料前体并在200°C下固化，然后在微波腔或常规电炉中接合而制成的。实验结果表明，在氧化锆和MaCor™的连接中，由于MaCor™的玻璃态性质，在连接或不连接中间层的材料之间都没有显着的界面微观结构和机械性能差异。由于MaCor™和二氧化硅的强润湿性和氧化锆的溶解，导致粘结界面不平坦。然而，在没有二氧化硅中间层的帮助下，在本研究的实验条件下，蓝宝石和98％的多晶氧化铝未能结合。已经观察到各种界面形态，包括非晶区域，细晶氧化铝以及蓝宝石和多晶氧化铝之间的紧密接触。另外，表征了从初始溅射固化到最终结合状态的结合过程的演变以及结合机理。本文的第二部分重点研究了加工和热处理对Ti-6Al-4V焊丝的组织，织构，相界移动和力学性能演变的影响。接收到的金属丝由平衡a相和亚稳态β相组成，并具有中等强度的纤维织构，其棱镜平面法线与金属丝轴对齐。通过挤压，固溶热处理，水淬火和时效处理金属丝。挤压过程增强了原样的质感。固溶和淬灭后，微结构观察表明在先前的β相区域中存在许多针状马氏体血小板。纹理分析表明，以初始纹理为代价出现了具有与线轴对齐的基面法线的辅助纤维，这表明在β→α转换过程中发生了高度优选的相边界运动（变量选择）。变体选择的强度随着固溶温度和时间的增加而持续增加。此外，进一步研究了位错类型和密度对变异选择的影响。这意味着可以利用战略性的先验变形和热处理来设计最终的织构和微观结构，从而优化钛产品的性能。

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