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High energy ball milling was performed on a mixture of titanium and aluminum elemental powders with a composition of Ti-48(at.%)Al. Stearic acid was added to this powder mixture as a process control agent (PCA) to study its effect on the microstructure evolution and crystallite size of the milled powder after various milling times. Phase compositions and morphology of the milled powders were evaluated using X-ray diffraction and scanning electron microscopy. Crystallite sizes of milled powders were determined by Cauchy-Gaussian approach using XRD profiles. It was shown that addition of 1wt.% of stearic acid not only minimizes the adhesion of milling product to the vial and balls, but also reduces its crystallite sizes. It has also a marked effect on the morphology of the final product.

In this study we utilized two types of plasma spray processing, namely atmospheric plasma spraying (APS) and hypersonic plasma spraying (HPS) to produce structural bulk titanium aluminides. Microstructure characterisation of the deposits, their compositional changes and phase transformations were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. It was found that the TiAl alloyed powder particles experienced a significant phase change during both APS and HPS processes. During APS the TiAl alloyed powder particles also experienced a significant compositional change; having a considerable amount of titanium oxides. On the other hand, the compositional change during HPS was negligible. At the end of the paper, an attempt of using a low temperature spraying process, i.e. cold gas dynamic spray, was reported as an alternative coating method.

Laser cladding of the Fe₃Al + B₄C/TiN + Al₂O₃ pre-placed powders on the Ti-6Al-4V alloy can form the Ti₃Al/Fe₃Al + TiN/TiB₂ composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti₃Al/Fe₃Al + TiN/TiB₂ composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al₂O₃ can react with TiB₂, leading to the formations of Ti₃Al and B. This principle can be used to improve the Fe₃Al + B₄C/TiN laser-cladded coating on the Ti-6Al-4V alloy. Furthermore, during the cladding process, C consumed the oxygen in Fe₃Al + B₄C /TiN + Al₂O₃ molten pool, which retarded the productions of the redundant metal oxides.