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The negative effects of thermal cycles in the process of additive manufacture present a challenge for the control of microstructure so as to fabricate the products with improved properties compared with conventional casting technique. In this work, AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) was prepared by laser metal deposition (LMD). Compared with conventionally cast EHEA samples, the LMD-fabricated EHEA samples showed significantly enhanced tensile strength (by 19.7%) and increased tensile ductility (by 56.4%). Such enhancement in tensile properties was attributed to the refinement of the uniformly distributed eutectic-structure, which improved the strain hardening/dislocation accumulation capability of the EHEA. The present work provides a new strategy to utilize both the high cooling rates of LMD and the eutectic-structure characteristics for forming refined homogeneous structures and thus achieving superior mechanical properties to those prepared by traditional processing techniques. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to analyze the undulated work-hardening behavior of S30408 metastable austenitic stainless steel at liquid nitrogen (LN 2) temperature. The flow stress curve, work-hardening process, strength, and ductility were studied by uniaxial tensile tests at both room temperature (RT) and −196 °C. Based on the scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) observations, the effects of the cryogenic temperature and deformation degree on the dislocation evolution, phase transformation, slip behavior, and hardening behavior were analyzed. The cryogenic work-hardening mechanism regarding the initial hardening, undulated hardening, and unstable hardening throughout the whole tensile process was elaborated. The correlation between macroscopic work-hardening and microscopic martensitic transformation accompanied by a localized dislocation strengthening was illuminated. It was revealed that the high strength of the austenitic steel during the cryogenic deformation process resulted from the α′-martensite transformation accompanied by dislocation strengthening. A critical point of phase content was obtained at a strain of 0.095 at −196 °C. The undulated work-hardening at cryogenic temperature was mainly attributed to the alternating evolution of the α′-martensite and austenite phases with a non-uniform deformation mode. • The undulated work-hardening behavior of a metastable austenitic stainless steel was investigated at liquid nitrogen temperature. • The effects of cryogenic temperature and deformation degree on work-hardening behavior were analyzed. • The correlation between macroscopic work-hardening and microscopic martensitic transformation was illuminated. • An obvious critical point of phase content was obtained at a strain of 0.095 at −196 °C. [ABSTRACT FROM AUTHOR]