Grain boundary serration tuning and its effect on hot workability of a wrought superalloy

Tso-Wei Chen (1, 2) , Pei-Te Wang (3) , Yung-Chang Kang (4) , Bo-Cheng Wu (5) , Nien-Ti Tsou (3) , Uwe Glatzel (6) , Stéphane Gorsse (7) , An-Chou Yeh (8, 9, 1)

1 PhD. Program in Prospective Functional Materials Industry,
2 High Entropy Materials Center
3 Department of Materials Science and Engineering
4 Gloria Material Technology Corporation
5 S-Tech Corporation
6 Metals and Alloys
7 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
8 Department of Materials Science and Engineering
9 High Entropy Materials Center

This study aims to elucidate the underlying mechanism of grain boundary serration and investigate its effects on hot workability of U720Li superalloy. Industrial scale as-cast ingots were subjected to heat treatments at 1180 °C followed by different cooling rates (15 °C/s, 0.1 °C/s, 0.02 °C/s and 0.003 °C/s) prior hot deformation. With 15 °C/s fast cooling, samples possessed straight boundaries and fine L12 structured γ’ particles dispersion. When the cooling rate was decreased to 0.1 °C/s and below, continuous and discontinuous precipitation of the γ' phase led to the formations of Type-I and Type-II grain boundary serrations, respectively. Lamellar γ/γ’ behind the mobile grain boundary was observed for Type-II boundary, which exhibited larger degree of undulation than that of Type-I boundary. With increasing fractions of Type-II boundary, the hot formability of U720Li was significantly improved during compression tests at 1000 °C; 70 % reduction ratio (true strain=1.2) could be achieved without crack formation. This work presents a simple process route to improve the hot deformability of U720Li fabricated on an industrial scale.

Domaines: Matériaux

Tso-Wei Chen, Pei-Te Wang, Yung-Chang Kang, Bo-Cheng Wu, Nien-Ti Tsou, et al.. Grain boundary serration tuning and its effect on hot workability of a wrought superalloy. Journal of Alloys and Compounds, 2023, 960, pp.170620. ⟨10.1016/j.jallcom.2023.170620⟩. ⟨hal-04112884⟩