Microstructure Design and Its Effect on Mechanical Properties in Gamma Titanium Aluminides

Abstract

Intermetallic gamma titanium aluminides display attractive engineering properties at high temperatures of up to 750 °C. To date, they have been used in low-pressure turbine blades and turbocharger rotors in advanced aircraft and automotive engines. This review summarizes the fundamental information of the Ti–Al system. After providing the development of TiAl alloys, typical phases, microstructures and their characteristics in TiAl alloys, the paper focuses on the effects of alloying elements on the phase boundary shifting, stabilizing effects and strengthening mechanism. The relationships between chemical additions, microstructure evolution and mechanical properties of the alloy are discussed. In parallel, the processing technologies and the common heat treatment methods are described in detail, both of which are applied to optimize the mechanical properties via adjusting microstructures. On this basis, the effects from chemical composition, processing technologies and heat treatments on microstructure, which controls the mechanical properties, can be obtained. It has a certain guiding significance for tailoring the microstructures to gain desired mechanical properties.

A Review of the State of Art of Fabrication Technologies of Titanium Aluminide (Ti-Al) Based on US Patents

“…GE 48-2-2 [16] was chosen for the low-pressure turbine (LPT) blades of the GEnx engine, which is used in the gas turbine blade of the Boeing 787 aircraft, also, Ti-Al-based alloys help with weight reduction in the range of grams. The utilization of γ-TiAl in a commercial jet engine [17,18] marked a significant milestone. Ti-Al-based alloys entered service in 2011, representing the first large-scale use of γ-TiAl [19].…”

How Coherent and Semi‐Coherent Interfaces Govern Dislocation Nucleation in Lamellar TiAl Alloys

“…[7,9,10,[19][20][21] As a consequence, most experimental analysis and alloy design strategies do not or cannot explicitly differentiate between the kinds of rotational twin boundaries when studying deformation. [2,5,12,[25][26][27][28] Thus, there is a pressing need to resolve the individual influence of interfaces on deformation behavior.…”

“…The lamellar TiAl microstructure is abundant with twin boundary interfaces and alloy design strategies rely on ultimately adjusting the number of such interfaces and simultaneously changing the lamellar thickness. [ 1,6,12,13 ] However, due to the ordering and the resulting tetragonal nature of the γ phase, three different kinds of {111} boundaries exist—the pseudotwin (PT) boundary, with a misorientation of 60°, the 120° rotational fault boundary or rotational boundary (RB), and the true twin (TT) boundary with a rotation of 180°. [ 1 ] For RB and PT, a lattice mismatch exists at the interface which leads to condition of coherency stresses or misfit dislocations.…”

“…The previous distinction is essential, as alloy design criteria so far do not explicitly pay attention to the kind of interfaces formed during solidification [ 1,12 ] and studies mostly focus on the optimal spacing of these boundaries. Recent insights from tailoring nanolamellar materials [ 3,27,39,40 ] consisting entirely of coherent boundaries indicate that a drastic increase in plasticity is possible due to the presence of only coherent twin boundaries.…”

Role of SPS temperature and holding time on the properties of Ti3AlC2-doped TiAl composites

“…These unique properties have made them suitable choices to utilize in various high-temperature structural usages and automobiles [1][2][3][4]. However, the development and application of such materials have been restricted by their shortcomings like weak formability and lowtemperature ductility [5][6][7]. Therefore, utilizing a suitable consolidation technique and reinforcement introduction or changing the composition is an appropriate approach to overcome such weaknesses [8][9][10][11].…”