Y. Xia

Bio: Y. Xia is an academic researcher from University of Queensland. The author has contributed to research in topics: Sintering & Titanium aluminide. The author has an hindex of 1, co-authored 1 publications receiving 13 citations.

Microstructure evolution and tensile properties of conventional cast TiAl-based alloy with trace Ni addition

Abstract: The microstructure evolution and tensile properties of Ti-48Al-2Cr-2Nb-0.25Ni alloy fabricated by the induction skull melting (ISM) process were investigated. Results showed that the influence of trace Ni addition on the cast microstructure was slight, while the γ phase fraction increased relatively. After tensile tests at elevated temperature, nanoscale τ3 particles precipitated within the lamellar colony in the gauge area. The τ3 phase exhibited the specific orientation relationship with the α2 and γ phases: ( 22 4 2 ) τ 3 // ( 40 4 1 ) α 2 // ( 113 ) γ and [ 1 1 00 ] τ 3 //[11 2 0] α 2 //[ 1 10]γ . At elevated temperature, the UTS and ef were enhanced evidently by Ni addition than that of Ti-48Al-2Cr-2Nb alloy. Dislocations were pinned by the nanoscale τ3 precipitates during tensile deformation at elevated temperature. The nanoscale τ3 precipitates and increased γ phase fraction induced by Ni alloying could account for the notable tensile properties in the present work. The precipitation behavior and the main strengthening mechanism were analyzed and discussed in detail.

Pressureless sintering of titanium and titanium alloys: sintering densification and solute homogenization

Abstract: This chapter discusses the fundamental issues relevant to the sintering of commercially pure titanium (CP-Ti) and titanium alloys. It begins by providing a concise review of the stability of the surface oxide film on titanium powder. Experimental data suggest that noticeable dissolution of the surface oxide film on titanium powder starts from the temperature range of 615–674°C during heating (at 10°C/min), depending on powder characteristics. Following a brief discussion of the sintering of CP-Ti powder compacts, the rest of the chapter focuses on the sintering fabrication of titanium alloys containing slow diffusers. The decoupled sintering densification and solute homogenization issue is discussed in detail through the sintering of Ti-10V-2Fe-3Al (wt%). The importance of master alloy selection and design of appropriate sintering pathways is demonstrated for achieving both high sintering densification and solute homogenization. Also discussed is the use of sintering aids for enhanced sintering and microstructure modification.

High-temperature oxidation behaviour of TiAl alloys with Co addition

Abstract: The challenge of enhancing the high-temperature oxidation resistance of TiAl alloys is hereby addressed by Co addition. Isothermal oxidation tests were conducted on the newly designed TiAl-Co alloys in laboratory air at 900 °C up to 100 h. Sintered microstructure, oxidation kinetics, scale structure, spallation resistance and oxidation mechanisms were systematically investigated. Results show that the original sintered microstructure of TiAl alloys mainly consists of matrix phases α2-Ti3Al/γ-TiAl lamellae, while the Co addition leads to the formation of the two additional Co-rich phases of CoAl2Ti and Ti (Al, Co, Cr and Nb) at grain boundaries. The Co-doped TiAl alloys exhibit an improved high-temperature oxidation resistance compared with the Co-free alloy. The presence of the Co-rich phases network along the grain boundaries and Co-rich layer at the scale/substrate interface can hinder the inward diffusion of oxygen and the outward diffusion of Ti and Al, thereby suppressing the growth of oxide scale and improving the spallation resistance of TiAl alloys. As a result, the TiAl-3Co alloy possesses excellent oxidation resistance, with the minimum mass gain of 4.08 mg/cm2, thinnest scale thickness of 17.8 μm and without surface spallation or crack formation after isothermal oxidation for 100 h. This result would pave the way for designing high-temperature oxidation-resistant TiAl-based alloys.