Papers by Author: Li Juan Xu

Abstract: The fabrication of ceramic moulds with zirconia primary coat for investment casting of gamma titanium aluminide based alloys (hereafter called TiAl alloys) was described in this study. The microstructures and fracture strength of ceramic moulds were characterized. The fracture strength and surface roughness of the ceramic moulds with zirconia primary coat were sufficient for the TiAl investment casting. TiAl blades were used for the technology demonstration in producing TiAl components. TiAl castings produced by the ceramic moulds exhibited an average surface roughness (R_a ) of 6 μm.

Abstract: γ-TiAl components due to their unique properties are on the verge of industrial application for increasing operation temperature and improving energy efficiency, especially in aerospace and automobile areas. This paper describes the recent developments of hot precision processing in ingot metallurgy technology including investment casting, canned forging and sheet rolling of TiAl alloys. Alloys development and the melting technology were discussed. Investment casting of TiAl alloys has been successfully developed to manufacture net-shape components. Research aimed at producing TiAl sheets through canned forging and rolling is introduced.

Abstract: In the present study, we tried to make Ti matrix/hydroxyapatite biocomposites using powder metallurgy and chemical treatments. Three composites were produced: Ti-30vol%HA, Ti15Mo-30vol%HA and Ti13Nb13Zr-44vol%HA. After mechanical milling and spark plasma sintering, Ti/HA composite compacts were produced. Microstructure observations and mechanical property tests showed that composites with two components (Ti-HA) have high hardness, moderate compress strength and lower density. The produced Ti/HA bulk composites were subjected to chemical treatment of immersion into phosphoric acid solution and porous structure was obtained. The obtained porous structure was characterized.

Abstract: In this paper, numerical simulation software of AnyCasting was adopted for simulate processes of titanium aluminum alloys filling and solidifying. Pour temperature, pressure head and rotate speed had an important effect on casting quality. The former parameters as factors orthogonal experiment L7 (33) was carried out and the experimental scheme was optimized. The results showed that as the pour temperature rising the filling time had no change, solidifying time had a large increase and casting defect tendency tended to little. Filling time and solidifying time decreased with the pressure head rising and casting defect tendency changed from little to large. The effect of rotating speed on filling time was as that of pressure head, solidifying time had little change and casting defects tendency of casting changed from little to great. With the optimized parameters of casting temperature of 1650°C, pressure head of 0.2m and rotating speed of 200r/min the investment cast filling and solidifying simulations was made out. The results showed that in the optimized simulation the liquid metal filled mold from the top down, filling course was smooth and complete and temperature field was even. Through analyses of casting defects the optimized scheme proved to be logical.