Research on aluminum component change and phase transformation of TiAl-based alloy in electron beam selective melting process under multiple scan

Microstructure evolution and mechanical properties of TiAl binary alloys added with SiC fibers

The microstructure and tensile properties of β-containing Ti–44Al–4Cr alloy rods additively manufactured by electron beam melting (EBM) process were examined as a function of input energy density determined by the processing parameters. To the best of our knowledge, this is the first report to demonstrate that two types of fine microstructures have been obtained in the β-containing γ-TiAl alloys by varying the energy density during the EBM process. A uniform α2/β/γ mixed structure containing an α2/γ lamellar region and a β/γ dual-phase region is formed at high energy density conditions. On the other hand, a lower energy density leads to the formation of a peculiar layered microstructure perpendicular to the building direction, consisting of a ultrafine α2/γ lamellar grain layer and a α2/β/γ mixed structure layer. The difference in the microstructures originates from the difference in the solidification microstructure and the temperature distribution from the melt pool, which are dependent on the energy density. Furthermore, it was found that the strength of the alloys is closely related to the volume fractions of the β phase and the ultrafine α2/γ lamellar grains which originates from the massive α grains formed by rapid cooling under low energy density conditions. The alloys with high amounts of these peculiar microstructures exhibit high strength comparable to and higher than the conventional β-containing γ-TiAl at room temperature and 1023 K, respectively.

Peculiar microstructural evolution and tensile properties of β-containing γ-TiAl alloys fabricated by electron beam melting

Microstructure and phase evolution in γ-TiAl/Ti2AlNb dual alloy fabricated by direct metal deposition

A Review of Microstructure Control and Mechanical Performance Optimization of γ-TiAl Alloys

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.

Jing Dong

Papers

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