Controlling crystallographic ordering in Mo-Cr-Ti-Al high entropy alloys to enhance ductility

JOURNAL OF ALLOYS AND COMPOUNDS

卷:823

Article

Laube, Stephan¹  Chen, Hans¹  Kauffmann, Alexander¹  Schellert, Steven²  Mueller, Franz²  Gorr, Bronislava²  Mueller, Julian²  Butz, Benjamin²  Christ, Hans-Juergen²  Heilmaier, Martin¹ 

[1] Karlsruhe Inst Technol, Inst Appl Mat IAM WK, Engelbert Arnold Str 4, D-76131 Karlsruhe, Germany

[2] Univ Siegen, Inst Werkstofftech, Paul Bonatz Str 9-11, D-57068 Siegen, Germany

关键词: High entropy alloys (HEA);    Crystal structure;    Calorimetry;    Mechanical properties;    Ductility;    Transmission electron microscopy (TEM);   

DOI  :  10.1016/j.jallcom.2020.153805

来源: Elsevier

【 摘 要 】

Refractory high entropy alloys (RHEAs) from the Mo-Cr-Ti-Al system exhibit promising strength at elevated temperatures. However, at room temperature they possess a B2-ordered crystal structure and, therefore, exhibit reduced ductility. Guided by thermodynamic calculations, the Al concentration was systematically reduced in MoCrTi-xAl (x = 25, 15, 10, 5, 3 at%) in order to achieve a disordered, solid solution with A2-type crystal structure even at room temperature. The alloys were manufactured by arc melting followed by a homogenization treatment. To evaluate the chemical homogeneity, backscatter electron (BSE) imaging and energy dispersive X-ray spectroscopy (EDS) were performed. Dynamic differential scanning calorimetry (DSC) and selected area diffraction utilizing transmission electron microscopy (TEM-SAD) were performed for the: (i) detection of the characteristic heat signatures of the disorder-order transformations and (ii) determination of the ordering state at room temperature of the synthesized alloys, respectively. In case of MoCrTi-3Al, a single-phase A2 crystal structure without indications of a disorder-order transformation was obtained. Compression tests at temperatures ranging from room temperature up to 800 degrees C reveal a significant improvement of plastic deformability at room temperature as compared to the formerly investigated equiatomic MoCrTiAl with its B2 crystal structure. (C) 2020 Elsevier B.V. All rights reserved.

【 授权许可】

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