In order to improve the strength of 5083 Al alloy used in a wide range of industries, incorporation of multi-walled carbon nanotubes (MWCNTs) into 5083 Al alloy by the use of friction stir processing (FSP) was investigated. The MWCNT-reinforced Al alloy composites via FSP were successfully fabricated. The composites have no voids and other defects with the optimized conditions of FSP. The grain refining and uniform distribution of MWCNTs were achieved because the composite powder comprised of MWCNTs and 5083 Al alloy via ball milling was used as a reinforcement. Nanoparticles of MWCNTs and submicron particles were observed in the composite. The proof stresses of the composites increased by ranging from 53 to 61 percent compared with that of the base material and the tensile strengths increased by ranging from 13 to 16 percent.

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In order to improve high-temperature oxidation resistance of titanium, fabrication of TiAl intermetallic compounds as a surface layer by plasma transferred arc surfacing (PTA surfacing) was investigated. Powder of unalloyed aluminum was fed into the plasma during the PTA surfacing and TiAl-based intermetallic layers were successfully synthesized. The surface layers had no cracks and porosities with optimized conditions of the PTA surfacing. The surface layers that largely consist of TiAl and Ti 3 Al phase could be achieved, while the microstructures of them were significantly influenced by the conditions such as the arc current. The TiAl-based layers exhibited high resistance to oxidation under isothermal conditions at 1073 K or less and had practically the same resistance as SUS310S had.

In order to enhance the strength of 5083 Al alloy, fabrication of multi-walled carbon nanotubes (MWCNTs) reinforced 5083 Al alloy by the use of friction stir processing (FSP) was investigated. The MWCNT-reinforced Al alloy composites using sintered sheets of 5083 Al alloy-8%MWCNT were successfully fabricated. Grain refinement and many minute aluminum carbides (Al 4 C 3 ) were observed in the composites fabricated. The proof stress of the composites fabricated with the 550°C sintered sheets considerably increased by 153 percent and the tensile strength increased by 55 percent compared with that of the base material. [

In this work, a feasibility study has been conducted on the formation of NiTi intermetallic compound coating by plasma transferred arc (PTA) surfacing process. The filler materials used were alloyed powder of NiTi and physically mixed powder of nickel and titanium. Wear characteristics of the coatings were evaluated by a modified Okoshi-type wear tester.It was found that it is possible to produce intermetallic compound coatings from the mixed powder as well as alloyed powder by PTA surfacing process. The wear resistance of the coatings formed from alloyed powder (the NiTi coating) is superior to the resistance of Stellite ♯6 coatings. The coatings formed from mixed powder (the Ni＋Ti coating) have wear resistance similar to that of Stellite ♯6 coatings. X-ray diffraction result indicates that the NiTi coatings mainly consist of NiTi phase, whereas the Ni ＋Ti coatings principally consist of NiTi and FeTi phases. Hardness values of both NiTi and Ni＋Ti coatings reached to 800HV or more, and then minute cracks were observed in both coatings.