Materials Processing and Microstructure

The microstmcture exhibited by a polycrystalline sample is dependent on the conditions used during materials processing. In this section, we will discuss three types of materials processing and the manner in which they influence microstructuie. 

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Less pronounced thermal diffusion provides better lateral and depth resolution and is the basis of successful application of femtosecond pulses in material processing and microstructuring [4.231, 4.232]. All-solid-state femtosecond lasers with a pulse duration of 100-200 fs and a pulse energy of approximately 1 mj have recently become commercially available [4.233, 4.234]. 

During catalyst production, various process factors have effects on the material properties and microstructures of catalyst particles, and hence have effects on the... 

The present work continues our investigations of high strength and ductility in SPD-produced metals and focuses on analysis of critical SPD processing and microstructural parameters resulting in appearance of unique properties. Several UFG materials exhibiting extraordinary mechanical behaviour are studied and discussed in the present research pure Cu [4], CP Ti [4,9] and the Cu+0.5%A12O3 composite [10]. 

The microstructure of a metal often plays a critical role in the corrosion process. Therefore, it is critical to choose the material stock for testing carefully. Microstructure can change depending on the form of the material, that is, plate, rod, sheet, or thin film. End grains of a worked structure are often more susceptible to attack. Temper can play a very important role in the corrosion of A1 alloys. Ideally, the material used in experiments should be identical to that used in the real application. If the form of the material is unknown, it might be of interest to investigate the role of processing and microstructure on the corrosion process. 

Chemical composition of key component determines the properties of the ceramics, while small quantities of other components will have significant effect on the processing and microstructural development of the materials. Low concentrations of dopants in the range of 0.1-10 at.% are usually used to enhance the sintering behavior and modify the microstructure. Trace impurity elements at concentrations less than a few hundred parts per million (ppm) are inevitably present even in the cleanest powders, which could also have significant effect, which has however often been overlooked. For lab-scale experiments of transparent ceramics, element analysis is generally not an indispensable step, because the main components and additives have aU been predesigned. 

The technical progress against the major tasks is described. The major tasks are 1) Material Selection and Characterization 2) Material Processing and Process Control 3) Development and Application of NDE 4) Property Testing and Microstructural Evaluation 5) Reporting 6) Quality Assurance. 

The major, minor, and trace elements present in a powder can all have a significant influence on the subsequent processing and microstructural development of the material. Changes in the concentration of the major elements may resnlt from different powder synthesis methods or from changes in the synthesis conditions. Small concentrations of dopants ( 0.1 to 10 at%) are commonly added to improve processing and properties. Trace impurity elements at concentrations less than a few hundred parts per million are invariably present even in the cleanest powders. 

The effect of materials chemistry and microstructure of materials in SCC and the interrelationship between the two is highly complex. The composition of the alloy has a significant bearing on the properties of the passive films and phase distribution. For example, a high amount of carbon in steels tends to form chromium carbide which causes sensitization of steel and leads to intergranular corrosion. Similarly, impinity elements in steels segregates and affects the corrosion dissolution process. 

Simner, S. R, Xiao, R, Derby, B. (1998). Processing and microstructural characterization of RBSiC-TaSi2 composites. Journal of Materials Science, 33, 5557-5568. doi 10.1023/A 1004447727931. 

M. F. Ashby and D. R. H. Jones, Engineering Materials 2 Mn Introduction to Microstructures, Processing and Design, Pergamon, Oxford, UK, 1973. 

Emphasizing process design and control for enviroinnental protection and process safety. Microstructured Materials (Chapters 5 and 9)... 

The modern discipline of Materials Science and Engineering can be described as a search for experimental and theoretical relations between a material s processing, its resulting microstructure, and the properties arising from that microstructure. These relations are often complicated, and it is usually difficult to obtain closed-form solutions for them. For that reason, it is often attractive to supplement experimental work in this area with numerical simulations. During the past several years, we have developed a general finite element computer model which is able to capture the essential aspects of a variety of nonisothermal and reactive polymer processing operations. This "flow code" has been Implemented on a number of computer systems of various sizes, and a PC-compatible version is available on request. This paper is intended to outline the fundamentals which underlie this code, and to present some simple but illustrative examples of its use. 

Fabrication processing of these materials is highly complex, particularly for materials created to have interfaces in morphology or a microstructure [4—5], for example in co-fired multi-layer ceramics. In addition, there is both a scientific and a practical interest in studying the influence of a particular pore microstructure on the motional behavior of fluids imbibed into these materials [6-9]. This is due to the fact that the actual use of functionalized ceramics in industrial and biomedical applications often involves the movement of one or more fluids through the material. Research in this area is therefore bi-directional one must characterize both how the spatial microstructure (e.g., pore size, surface chemistry, surface area, connectivity) of the material evolves during processing, and how this microstructure affects the motional properties (e.g., molecular diffusion, adsorption coefficients, thermodynamic constants) of fluids contained within it. 

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