TY - JOUR

T1 - Microstructural influences on fatigue threshold behavior and fracture toughness of an additively manufactured γ-titanium aluminide

AU - Zeiler, Stefan

AU - Lintner, Arthur

AU - Schloffer, Martin

AU - Pippan, Reinhard

AU - Hohenwarter, Anton

N1 - Publisher Copyright: © 2023 The Authors

PY - 2023/2/22

Y1 - 2023/2/22

N2 - The fracture and fatigue behavior of an additively manufactured γ-TiAl alloy (BMBF3) produced by selective electron beam melting and further subjected to two different heat treatment conditions was investigated. As one of the heat-treatments led to a pronounced layer structure, the experiments were also performed with different specimen orientations to account for possible anisotropy effects. In order to characterize the frequently found peculiarities of the local fracture process in this material class, such as shear ligament bridging, static and cyclic R-curves were recorded. In addition, also fatigue crack growth curves were measured. The results were critically compared with the properties of a selected heat treatment condition of an established TNM alloy manufactured by a conventional processing route. The investigations show that large α 2/γ-colonies lead to high fracture toughness, but have almost no positive effect on the long-crack fatigue threshold. On the other hand, duplex microstructures with small α 2/γ-colonies and thick lamellae favor high long-crack thresholds, but low fracture toughness. Microstructures with high fractions of globular γ-phase exhibited both, low fracture toughness and low long-crack fatigue threshold values. In comparison to the established TNM reference alloy, the additively manufactured counterparts can compete especially when the evolving anisotropy of the properties is taken into account for component design.

AB - The fracture and fatigue behavior of an additively manufactured γ-TiAl alloy (BMBF3) produced by selective electron beam melting and further subjected to two different heat treatment conditions was investigated. As one of the heat-treatments led to a pronounced layer structure, the experiments were also performed with different specimen orientations to account for possible anisotropy effects. In order to characterize the frequently found peculiarities of the local fracture process in this material class, such as shear ligament bridging, static and cyclic R-curves were recorded. In addition, also fatigue crack growth curves were measured. The results were critically compared with the properties of a selected heat treatment condition of an established TNM alloy manufactured by a conventional processing route. The investigations show that large α 2/γ-colonies lead to high fracture toughness, but have almost no positive effect on the long-crack fatigue threshold. On the other hand, duplex microstructures with small α 2/γ-colonies and thick lamellae favor high long-crack thresholds, but low fracture toughness. Microstructures with high fractions of globular γ-phase exhibited both, low fracture toughness and low long-crack fatigue threshold values. In comparison to the established TNM reference alloy, the additively manufactured counterparts can compete especially when the evolving anisotropy of the properties is taken into account for component design.

UR - http://www.scopus.com/inward/record.url?scp=85148546523&partnerID=8YFLogxK

U2 - 10.1016/j.intermet.2023.107852

DO - 10.1016/j.intermet.2023.107852

M3 - Article

VL - 156.2023

JO - Intermetallics

JF - Intermetallics

SN - 0966-9795

IS - May

M1 - 107852

ER -