No abstract

No abstract

Segregation can seriously damage the mechanical properties of the aluminum alloys. 6061 aluminum alloy wheel spokes were prepared by squeeze casting. To investigate the formation mechanism of segregation, the microstructure of the alloy was observed using scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and electron microprobe analysis methods. The Gibbs energy of each phase during solidification was calculated by JMatPro. Results show that the segregation phases in the R-joint of the wheel spokes are mainly composed of Mg 2 Si, β-AlFeSi and Al 5 Cu 2 Mg 8 Si 6 intermetallics. During the solidification of the 6061 aluminum alloy wheels, Mg 2 Si and α-AlFeSi phases precipitate in the mushy zone at first. With the decrease of temperature, α-AlFeSi transforms into β-AlFeSi, while Al 5 Cu 2 Mg 8 Si 6 precipitates from the solid-state aluminum alloy after solidification. Segregation at the R-joint of wheel spokes is mainly caused by insufficient cooling, so the cooling during alloy solidification should be enhanced to avoid segregation.

TiAl alloys have the advantageous properties of high specific strength, high specific stiffness, and excellent oxidation resistance, which have been utilized for turbine blades in aircraft engines and automobile engines [1][2][3] . The blades are used in high-temperature conditions, with oxidation resistance being one of the important indices in determining its application potential. TiAl alloys can exhibit good oxidation resistance after long-term thermal exposure at 700 °C [4] . But, when the temperature exceeds 800 °C, the continuous and dense Al 2 O 3 protective oxide film cannot be generated on the surface, and instead a mixed oxide consisting of TiO 2 and Al 2 O 3 is formed. TiO 2 has a loose structure and large oxygen permeability, which cannot prevent the diffusion of O atoms, resulting in insufficient oxidation resistance; thus, restricting their further application [5][6][7][8] . Therefore, enhancing the oxidation resistance of TiAl alloys above 800 °C has become an urgent problem [9] . Domestic and foreign scholars have obtained results regarding the oxidation resistance of TiAl alloys [10,11] . Studies

No abstract