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

Tetsui, Toshimitsu

doi:10.3390/met11091361

Cited by 6 publications

(2 citation statements)

References 14 publications

(13 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, the β phase is unnecessary for jet engine blades. In other words, although TiAlforged material [34][35][36], which is premised to contain the β phase for improving forgeability, is still useful as materials for large-area plates [37] or large structural components [38] difficult to make via casting, its use for small-sized products that can be manufactured by casting is questionable.…”

Section: Creep Strength and Comprehensive Evaluationmentioning

confidence: 99%

Effect of Microstructure on Impact Resistance and Machinability of TiAl Alloys for Jet Engine Turbine Blade Applications

Tetsui

2023

Metals

Self Cite

View full text Add to dashboard Cite

The impact resistance and machinability of TiAl alloys, which are used for jet engine turbine blades, are critical for ensuring reliability and reducing manufacturing costs. This study investigated the effects of the microstructure on these properties using Ti–Al–Cr ternary alloys via Charpy impact tests at room temperature and 700 °C and performing cutting tests using a face mill with cemented carbide tools. As a result, it was confirmed that six types of typical microstructures of TiAl alloys, namely, fine FL, coarse FL, L + γ, γ, γ + β, and L + γ + β, could be formed by varying the Al and Cr concentrations and heat-treatment conditions. Impact resistance and machinability are each the exact opposite trends to the other, with coarse FL having the best impact resistance but poor machinability. Meanwhile, γ has the best machinability but the weakest impact resistance. L + γ has no major drawbacks, including creep strength. As the microstructure of TiAl4822, currently used in LEAP (leading edge aviation propulsion) engine blades, is almost a γ single-phase microstructure, we assumed that manufacturers chose this microstructure to improve machinability and thus reduce the cost. However, because the γ microstructure has the lowest impact resistance, caution should be exercised when applying it to other engines with different operating environment. On the other hand, the microstructure containing the β phase is inferior in all aspects, including creep strength. Thus, it is questionable to use TiAl-forged materials with a residual β phase in small-sized products that can be manufactured by casting.

show abstract

Section: Creep Strength and Comprehensive Evaluationmentioning

confidence: 99%

Effect of Microstructure on Impact Resistance and Machinability of TiAl Alloys for Jet Engine Turbine Blade Applications

Tetsui

2023

Metals

Self Cite

View full text Add to dashboard Cite

show abstract

“…The lattice parameters and composition vary among different phases. Significant phase transformation occurs when the TiAl alloy is heat treated above the eutectoid transition temperature (T eu , between about 1100 °C and 1200 °C) [ 1 , 7 , 8 , 9 ]. The phase transformation rate and trend are primarily influenced by temperature conditions, a non-equilibrium state induced by the cooling rate, and external stress conditions.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Evolution of the Ti-46Al-8Nb-2.5V Alloy during Hot Compression and Subsequent Annealing at 900 °C

Cao,

Li,

et al. 2023

Materials

View full text Add to dashboard Cite

TiAl alloys are high-temperature structural materials with excellent comprehensive properties, and their ideal service temperature range is about 700–950 °C. High-Nb containing the Ti-46Al-8Nb-2.5V alloy was subjected to hot compression and subsequent annealing at 900 °C. During hot compression, work-hardening and strain-softening occurred. The peak stresses during compression are positively correlated with the compressive strain rates and negatively correlated with the compression temperatures. The α2 phase exhibited a typical (0001)α2 basal plane texture after hot compression, while the β0 and γ phases did not show a typical strong texture. Subsequent annealing at 900 °C of the hot-compressed samples resulted in significant phase transformations, specifically the α2 → γ and β0 → γ phase transformations. After 30 min of annealing, the volume fraction of the α2 phase decreased from 39.0% to 4.6%. The microstructure characteristics and phase fraction after 60 min of annealing were similar to those after 30 min. According to the calculation of Miller indexes and texture evolution during annealing, the α2 → γ phase transformation did not follow the Blackburn orientation relationship. Multiple crystal-oriented α2 phases with nanoscale widths (20~100 nm) precipitate within the γ phase during the annealing process, which means the occurrence of γ → α2 phase transformation. Still, the γ → α2 phase transformation follows the Blackburn orientation relationship.

show abstract