The interaction and migration of deformation twin in an eutectic high-entropy alloy AlCoCrFeNi2.1

doi:10.1016/j.jmst.2018.09.067

Abstract

Abstract:

An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600-700 °C. The microstructure reveals the intersection of twin-twin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and Π were formed by the edge dislocation 112ˉ and the mixed dislocation 211ˉ on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength (the tensile strengths at the 600° and 700° tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.

Key words: Eutectic high-entropy alloy, Tensile properties, Deformation twin, Dislocation jog, Twin migration

Yaoli Zhang, Jinguo Li, Xinguang Wang, Yiping Lu, Yizhou Zhou, Xiaofeng Sun. The interaction and migration of deformation twin in an eutectic high-entropy alloy AlCoCrFeNi_2.1[J]. J. Mater. Sci. Technol., 2019, 35(5): 902-906.

Figures/Tables 5

Fig. 1 Phase structure, SADPs and EDS of the as-cast alloy. (a) EBSD phase map, (b) TEM morphology, (c, d) the SADPs and EDS obtained from the dual-phase in TEM, respectively.

Fig. 2 (a-c) Bright field TEM image of the EHEA after tensile deformation at the 600?°C-700?°C, and (d, e) corresponding electron patterns along the [011] zone axis, (f) high-resolution transmission electron microscopy (HRTEM). Inserts are the corresponding fast Fourier transformations (FFT).

Fig. 3 The schematic illustration of twin-twin interaction. (a, b) Intercrossing of dislocation AB and dislocation CD, (c, d) Intercrossing of dislocation AB and dislocation C′D′.

Fig. 4 EPMA element mapping. (a-d) Microstructure and the relative content of Fe, Co, Cr elements of the as-cast alloy, (e-h) Microstructure and the relative content of Fe, Co, Cr elements of the alloy after deformation.

Fig. 5 Engineering stress-strain curves of the AlCoCrFeNi2.1 EHEA in the as-cast at the rate of 1?×?10-3/s and temperatures of room temperature, 600?°C, 700?°C and 800?°C.

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