Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7974328 | Materials Science and Engineering: A | 2018 | 7 Pages |
Abstract
Ti44Al6Nb1Cr (at%) alloys with different lamellar spacing were prepared by cold crucible directional solidification. Creep tests were conducted at 750 °C under 260 and 300 MPa, and the microstructure before and after creep testing were observed and analyzed. The results show that the prepared TiAl alloys have similar macro/microstructure except for lamellar spacing, which are different from the heat-treated TiAl alloys with obviously changed macro/microstructure. The refinement of lamellar spacing can improve creep properties, especially the steady-state of fine lamellar alloy lasted for more than 600 h with creep rate at 7.3 à 10â9 Sâ1. The improvement of creep properties by refined lamellar spacing are revealed as following two reasons. (1) Fine lamellar spacing improves the stability of γ lamellae and increases the resistance for dislocation slip in γ lamellae. (2) It disperses stress concentration and delays the formation of globular structure at colony boundary. Moreover, the alternating β and γ laths in α-segregation zone can improve microstructural stability during creep. In β-solidifying γ-TiAl alloy, the local stress concentration on β-segregation at colony boundary promotes colony boundary sliding and the formation of void with globular structure, which further accelerates the creep failure.
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Authors
Qi Wang, Ruirun Chen, Yaohua Yang, Shiping Wu, Jingjie Guo, Hongsheng Ding, Yanqing Su, Hengzhi Fu,