Ductile and ultrahigh-strength eutectic high-entropy alloys by large-volume 3D printing

3D printing of high-strength alloys enables efficient manufacturing of complex metallic components. Yet, the as-built parts are often characterized by unsatisfied ductility due to micro-defects, requiring additional heat treatment to optimize the structure before in-site applications. The post heat-processing, however, often changes the shape of the printed parts, deteriorating the quality of the printed components. In addition, many printed large-scale alloy parts with complex shapes are difficult to be processed by hot isostatic pressing. This requires that the alloys can be printed with good strength and ductility without the necessity of additional thermal processing. Here, we show that excellent ductility and ultrahigh strength can be achieved in a eutectic high-entropy alloy (EHEA) by large-volume 3D printing. The as-printed EHEA has a tensile yield strength of 1040 MPa, and a total elongation of 24%, as well as superior corrosion resistance in seawater environment. The excellent combination of properties outperforms that of all other existing metallic materials. Note that these astonishing properties are from specimens directly after 3D printing without any subsequent heat treatment and hot isostatic pressing. The exceptional mechanical properties are mainly ascribed to the fine lamella spacing in the composite structure consisting of face-centered cubic matrix and B2 precipitates, which renders high resistance for dislocation movement and extends work hardening capability. The EHEA printed in large volume without post processing thus shows high applicability for mass-production at an industrial scale.