Precipitation Process in Fe-Ni-Al-based Alloys

This chapter covers first the precipitation and coarsening processes in Fe-Ni-Al alloys aged artificially at high temperatures, as well as their effect on the mechanical properties. These results show the precipitation evolution, morphology of precipitates, coarsening kinetics and mechanical properties such as hardness. Additionally, the effect of alloying elements such as copper and chromium is also studied on the precipitation and coarsening processes. The main results of this section are concerning on the coarsening kinetics and its effect on hardness. Besides, the diffusion couple method is employed to study the precipitation and coarsening process in different Fe-Ni-Al alloy compositions, as well as its effect on the hardness. All the above aspects of precipitation and coarsening are also supported with Thermo-Calc calculations

Study of Mechanical, Thermal, and Microstructural Properties of Polypropylene/Ceramic Waste Composites

In this work, the effect of reinforcement of the iPP with ceramic waste (CW), and the use of maleic anhydride compatibilizing agent grafted with polyolefin elastomer (POE-g-MAH) are studied. The composites were fabricated by extrusion and injection processes, and their morphology and microstructure, as well as fracture surface and mechanical and thermal properties were analyzed. Characterization by polarized optical microscopy showed that the ceramic waste particles were well-dispersed into the iPP matrix without the presence of agglomerates. However, the POE-g-MAH did not show good compatibility when it was added to the iPP/CW composite. Hardness Rockwell R, tensile and flexural measurements showed that the hardness, Young´s modulus, and flexural modulus increased with the incorporation of CW and without the POE-g-MAH. The ductility of the composites was several decreased with the addition of CW. POE-g-MAH affected the hardness, ductility, strength tensile, Young´s modulus, flexural modulus, and interfacial interaction in the iPP/CW composite. Analysis by X-ray diffraction showed that the CW also acted as a nucleating agent, increasing the crystallization degree, and forming the β-phase. Analysis of the Fourier transformed infrared showed transmittance bands of the iPP, CW, POE-g-MAH and composites. The bands were similar and there were no major changes in characteristic bands of composites, but CW and POE-g-MAH produced changes in the shape and intensity of band peaks of the iPP matrix. The CW addition to the iPP matrix modified the thermal properties of pure iPP, such as the degree of crystallization and melting temperature in the iPP/CW composites. The incorporation of POE-g-MAH decreased the crystallization temperature and crystallinity degree in the iPP/CW composite

Phase Transformations of 5Cr-0.5Mo-0.1C Steel after Heat Treatment and Isothermal Exposure

This study consists of the experimental and numerical analysis of the phase transformations of 5Cr-0.5Mo.0.1C steel after heat treatment. The microstructure of the as-received steel comprised ferrite and bainite, which is in agreement with the microconstituents predicted by the Calphad-calculated TTT diagram. Calphad-based precipitation calculations show that the cooling stage of normalizing treatment did not cause carbide formation. In contrast, tempering at 700 °C for 15 min promotes the intergranular precipitation of Fe3C, M7C3 and M23C6 carbides, which is consistent with experimental results. Aging at 600 °C for short periods caused the precipitation of both M7C3 and M23C6 carbides; however, M23C6 is the dominant phase after prolonged aging. This is in agreement with experimental results. A rapid decrease in the steel hardness was observed after short aging, which is attributable to bainite transformation. Further reduction in hardness is associated with the diffusion-controlled coarsening of M23C6 carbide