High Nb–TiAl Intermetallic Blades Fabricated by Isothermal Die Forging Process at Low Temperature

Abstract

In this study, the isothermal die forging process of high Nb–TiAl (Ti-44Al-8Nb-0.2W-0.2B-Y, at.%) alloy blades was simulated using the ABAQUS V6.11 software and the blades were fabricated successfully. The influence of a low forging temperature (lower than 1000 °C) and strain rate on the distributions of effective strain and stress were analyzed. The results indicate that the effective strain exhibits negative temperature sensitivity and positive strain rate sensitivity. The stress exponent (n = 3.02) and the apparent activation energy (Q = 293.381 kJ/mol) of the present alloy suggests that this as-forged high Nb–TiAl alloy exhibits good deformability at low temperatures. With the reduction in strain rate and the increase in forging temperature, the effective stress decreases. Finally, high-quality high Nb–TiAl alloy blades were fabricated using an isothermal die forging technology at a rate of 0.01 mm/s and temperature of 950 °C, chosen on the basis of the simulations results. Scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD) results indicated that the center of the TiAl alloy blade possessed a duplex microstructure, consisting of remnant lamellar colonies and recrystallized γ/B2 grains. The refined α2 laths showed a typical forging flow line feature in the edge position, whereas the γ laths had broken down and recrystallized.

Practical Use of Hot-Forged-Type Ti-42Al-5Mn and Various Recent Improvements

“…The turbine wheel in this product was cast TiAl alloy, which was manufactured by precision casting and joined to a low-alloy steel shaft to form the turbine rotor. Even in recent research on the practical application of TiAl alloys, small blades [2,3] and engine valves [4] manufactured by casting, isothermal forging, and extrusion are targeted, and there are no development examples of parts weighing 0.5 kg or more. The TiAl alloy is currently mostly used in the low-pressure turbine blades of jet engines [5] Parts manufactured by precision casting were initially used for practical applications; however, because the TiAl alloy is poorly castable, casting a near-net into a blade shape was difficult, with very large surplus materials required, leading to large amounts of machining that effectively negated the merits of precision casting.…”

Electrons Meet Alloy Development: A γ‐TiAl‐Based Alloy Showcase

“…Reproduced under the terms of the CC BY 4.0 license. [ 134 ] Copyright 2020, Xiaopeng Wang, Wenchen Xu, Peng Xu, Haitao Zhou, Fantao Kong, and Yuyong Chen. Reproduced with permission.…”

“…Different modeling techniques are suitable for different length scales and hence to address different problems. Left‐to‐right: finite‐element method (FEM) using continuum mechanics showing strain distribution in a blade made of TiAl−Nb alloy, [ 134 ] example of mesoscale modeling of dendrite growth in a β‐solidifying TiAl alloy using phase‐field modeling, [ 135 ] nanoscale atomistic simulation of a room‐temperature tensile test of γ‐TiAl, and valence charge distribution of plane of ‐Ti 3 Al. Reproduced under the terms of the CC BY 4.0 license.…”

“…Left-to-right: finite-element method (FEM) using continuum mechanics showing strain distribution in a blade made of TiAlÀNb alloy,[134] example of mesoscale modeling of dendrite growth in a β-solidifying TiAl alloy using phase-field modeling,[135] nanoscale atomistic simulation of a room-temperature tensile test of γ-TiAl, and valence charge distribution of ð0001Þ plane of α 2 -Ti 3 Al. Reproduced under the terms of the CC BY 4.0 license [134]. Copyright 2020, Xiaopeng Wang, Wenchen Xu, Peng Xu, Haitao Zhou, Fantao Kong, and Yuyong Chen.…”

EBSD Study of Delta-Processed Ni-Based Superalloy

“…This treatment includes an intentional δ-phase precipitation cycle as a preparation for the subsequent thermomechanical processing. It has been reported that DP718 can produce uniform fine grains [17][18][19][20][21][22][23][24]. Although DP718 is derived from a process known as "mini grain" mainly used in ingot-billet conversion [25][26][27], it also finds an opportunity as a possible industrial forging process.…”