High-temperature deformation mechanism of γ-TiAl-based alloy with ultrafine grains

Abstract

Equiaxed ultrafine duplex alloys γ-TiAl and α2-Ti3Al are prepared by high-energy milling and hot pressing sintering. Microstructures presenting in the mixed and sintered powders are studied by scanning electron microscopy. Structural characteristics are investigated by high-resolution electron microscopy before and after compression at 1100–1200°C. The data reveal grain sizes of 300–500 and ∼100 nm for sintered γ-TiAl and α2-Ti3Al alloys, respectively. High deformation temperatures and low strain rates lead to low peak flow stress, and at such conditions the α2/γ and α2/α2 interfaces are prone to forming dislocation structure. The studies also reveal the presence of large-angle grain boundaries for the [Formula: see text] and (0002)α2/(0002)α2 interfaces.

Creep behaviour of equiaxed fine-grain γ-TiAl-based alloy prepared by powder metallurgy

“…The powder was mechanically milled in a high-energy ball milling at 550 rev min −1 for 40 h. The particle of mechanical alloying formed a powder mass, and average powder size was about 500 nm after grinding. The preparation process was similar to the reported method in [11].…”

“…Microstructure of TiAl alloys significantly affects the high-temperature properties. The two-phase ( γ + α 2 ) alloys usually have better mechanical properties than single-phase γ alloys or α 2 alloys, because the uniformly distributed α 2 phase is acting as the reinforcement of γ phase [9,10], including the mechanisms of reinforcement of γ phase through α 2 interfaces [11,12]. TiAl alloys with such microstructure, which are commonly known as γ -TiAl base alloys, generally possess the best combination of room-temperature toughness and high-temperature strength [13].…”