No abstract

Intermetallic TiAl alloys are new generation high-temperature material. However, extensive application of TiAl alloys is hindered by some disadvantages, especially the high processing cost. Currently, precision casting is an effective method to manufacture TiAl components with complex shape. However, the interfacial reaction between the TiAl alloy melt and mould affects the quality of the castings and hinders extensive applications of casting TiAl components. In this paper, the research status of mould materials for the casting of TiAl alloys is reviewed. Performances of present used mould materials are compared in details. Reaction mechanisms between mould materials and the melts of TiAl alloys are also summarised. Finally, the future development tendency and prospect are pointed out.

For full-lamellar TiAl alloys, mechanical properties can be improved in a wide range of temperature by controlling lamellar orientation parallel to growth direction. However, lamellar controlled TiAl alloys with good properties and large scale are difficult to obtain due to sever interface reaction between TiAl melts and mould materials. In this paper, effect of lamellar orientation on tensile properties of directionally solidified (DS) Ti-46Al-0.5W-0.5Si alloy using oxide ceramics crucible was investigated. DS alloys with parallel lamellar structure had better tensile strength (479MPa) and elongation (0.76%) than that of specimen with equiaxed grains (428MPa, 0.22%). Fracture modes of DS alloys were interlamellar, translamellar mode and both, which depended on the lamellae orientation.

Glass fiber/poly(ether ether ketone) (GF/PEEK) composite foams with improved compressive strength and heat resistance can be successfully prepared using a simple and environmentally friendly supercritical carbon dioxide (sc‐CO2) foaming technology. The cell morphologies of the foams can be controlled by adjusting the GF content and foaming parameters, including the saturation temperature, saturation time, saturation pressure, and depressurization rate. With a foam density of 0.55 g cm−3, the PEEK‐based composite foam having 30% GF content has a 10% compressive strength of 11.07 MPa, and its density varies negligibly up to 330.0 °C. The GF/PEEK composite foams having high GF contents show significantly better properties than those having low GF contents as a result of the supporting and strengthening effect of the GF in the PEEK cell walls. The GF/PEEK composite foams also show good corrosion resistance. As a result of these properties, the GF/PEEK composite foams are promising high‐performance materials for use in extreme environments.

No abstract