Anomalous temperature dependence of yield strength and deformation mechanisms in chemically complex intermetallic alloy

Hou, Jinxiong and Gan, Jie and Wang, Tao and Luan, Junhua and Zhang, Tuanwei and Ren, Zhongkai and Zhang, Zhixiong and Wen, Wei and Wang, Zhihua and Song, Wenwen and Yang, Tao (2025) Anomalous temperature dependence of yield strength and deformation mechanisms in chemically complex intermetallic alloy. Materials Science and Engineering: A, 931: 148211. ISSN 0921-5093

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Abstract

An ordered L12 structure-dominated chemically complex intermetallic alloy (CCIMA) was developed based on a Ni-Co-Cr-Al-Mo-Ti-Ta-Nb-B system. Its phase structure, mechanical behaviors, and underlying deformation mechanisms were investigated systematically at room and elevated temperatures. The CCIMA yields at a strength of 758 ± 2 MPa at room temperature, maintaining a pronounced work-hardening rate of ∼ 4530 ± 10 MPa throughout the entire deformation, which achieves an ultimate strength of ∼ 1490 ± 12 MPa attributing to the formation of anti-phase boundary (APB) together with superlattice intrinsic stacking fault (SISF). A remarkable temperature-dependent anomaly in yield strength is formed at temperatures below about 800 °C, obtaining an increment of strength for nearly 200 MPa relative to that at 20 °C. Such yield strength anomaly (YSA) is caused by the pining of Kear-Wilsdorf (K-W) locks, resulting from thermally-activated superlattice dislocations from the (111) octahedral to (010) cube plane. Furthermore, a transition of dissociation scheme from APB-type at intermediate temperatures to SISF-type at 900 °C is believed to be responsible for the absence of YSA at higher temperatures. A high peak of flow stress towards 800 °C is formed in the CCIMA, signifying a great potential for elevated temperature applications.