Zhaohua Hu

Phase equilibria in the Y-Ti-Si system at 773 K

Abstract Physico-chemical analysis techniques, including X-ray powder diffraction, scanning electron microscopy, optical microscopy and differential thermal analysis were employed in constructing the isothermal section of the Y – Ti – Si system at 773 K. The isothermal section consists of 12 single phase regions, 21 binary phase regions and 10 ternary phase regions. No ternary compound is found in the work. None of the phases in this system reveals a remarkable homogeneity range at 773 K.

Phase diagram of the Al–Dy–Zr ternary system at 773 K

Abstract X-ray powder diffractometry, scanning electron microscopy, optical microscopy and differential thermal analysis were used for constructing the isothermal section of the Al–Dy–Zr system in the whole compositional range at 773 K. The existence of 13 binary compounds and 1 ternary compound, i.e. Al3Zr, Al2Zr, Al3Zr2, AlZr, Al3Zr4, Al2Zr3, AlZr2, AlZr3, α - Al3Dy, Al2Dy, AlDy, Al2Dy3, AlDy2, and Al30Dy7Zr3 were confirmed. The ternary compound Al30Dy7Zr3 has AuCu3 structure (space group Pm3m) with lattice parameter of a = 0.4206 nm. The isothermal section consists of 17 single-phase regions, 32 binary-phase regions and 16 ternary-phase regions. The homogeneity of Dy in the binary compounds Al3Zr, Al2Zr, Al3Zr2, and AlZr2 is determined to be 2 at.%, 3 at.%, 4 at.%, and 2 at.% Dy, respectively. The homogeneity range of Dy in Zr is up to v7 at.% Zr. The solid solubility of Zr in the binary compounds Al3Dy, Al2Dy, and AlDy is determined to be 2 at.%, 26 at.%, and 3 at.% Zr, respectively.

Influence of Cr on the microstructure and mechanical properties of Ti–Si Eutectic Alloys

Abstract As promising candidates for new high-temperature structural materials, Ti – Si eutectic alloys are required for the next generation of advanced aircraft engines. In this paper, microstructures of the Ti – Si eutectic alloys with various Cr contents were investigated by means of X-ray diffraction, scanning electron microscopy and light optical microscopy. The results show that with the increase of Cr content up to 9 wt.%, β-Ti (Si, Cr)ss matrix and Ti5Si3 form in the as cast alloy, however, the α-Ti (Si, Cr)ss phase disappears. Cr element solute in β-Ti and Ti5Si3 can significantly change the morphology and distribution of Ti5Si3 intermetallic phase. This greatly affects the fracture behavior and mechanical properties of as-cast Ti – Si eutectic alloys.