Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized high-entropy configurations against radiation damage. Here we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elements are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L1 0 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. These findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.

The role of the ferrite/cementite heterointerface on the mechanical properties of heavily-drawn-pearlitic steel is investigated via tensile deformation tests of multilayered composite models with brittle and ductile virtual materials in a two-dimensional triangle-lattice system by using molecular dynamics simulations. The interface strength is controlled by introducing a heterointerface potential. The dominant role of heterointerface on the mechanical properties of multilayered composite models is influenced by the interface strength. In case of weak interface strength, the heterointerface acts as a strong barrier to dislocation motion in the ductile phase; hence, the multilayered composite model shows high strength but extremely low ductility. This tendency corresponds well to that of as-drawn pearlitic steel with cementite decomposition. In case of strong interface strength, the heterointerface acts as a dislocation source of the brittle phase by dislocation transmission through the heterointerface from the ductile to brittle phase; hence, the multilayered composite model shows good ductility with a small decrease in strength. This tendency corresponds well to annealed pearlitic steel recovered from cementite decomposition. These results suggest that cementite decomposition decreases the plastic deformation potential of the heterointerface. The conditions necessary for the heterointerface to simultaneously exhibit high strength and ductility are discussed on the basis of the results of atomic simulations.

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Fracture toughness of silicon crystals has been investigated using indentation methods, and their surface energies have been calculated by molecular dynamics (MD). In order to determine the most preferential fracture plane at room temperature among the crystallographic planes containing the 001 , 110 and 111 directions, a conical indenter was forced into (001), (110) and (111) silicon wafers at room temperature. Dominant {110}, {111} and {110} cracks were introduced from the indents on (001), (011) and (111) wafers, respectively. Fracture occurs most easily along {110}, {111} and {110} planes among the crystallographic planes containing the 001 , 011 and 111 directions, respectively. A series of surface energies of those planes were calculated by MD to confirm the orientation dependence of fracture toughness. The surface energy of the {110} plane is the minimum of 1.50 Jm −2 among planes containing the 001 and 111 directions, respectively, and that of the {111} plane is the minimum of 1.19 Jm −2 among the planes containing the 011 direction. Fracture toughness of those planes was also derived from the calculated surface energies. It was shown that the K IC value of the {110} crack plane was the minimum among those for the planes containing the 001 and 111 directions, respectively, and that K IC value of the {111} crack plane was the minimum among those for the planes containing the 011 direction. These results are in good agreement with that obtained conical indentation.

The effects of alloy extrusion parameters, such as extrusion ratio, temperature, and speed on the mechanical properties at room and elevated temperatures and the microstructure evolution were investigated in the production of high strength Mg-Zn-Y alloys. The alloy used is a Mg 97 Zn 1 Y 2 (at%) which is engineered to acquire a long-period stacking ordered (LPSO) structure phase to increase alloy-strength. The microstructure of the extruded Mg 97 Zn 1 Y 2 alloy consists of hot-worked and dynamically recrystallized (DRXed) -Mg grains that includes a fiber-shaped LPSO phase elongated along the direction of extrusion. Whereas an increase in average equivalent strain promotes the DRX ofMg matrix and the dispersion of the fiber-shaped LPSO phase, an increase in average metal flow rate is conductive to the DRX of -Mg grains, but is not to the dispersion of LPSO phase. The mechanical properties of the extruded Mg-Zn-Y alloys are affected by changes in the area fraction of the DRXed grains and the dispersion of the fiber-shaped LPSO phase. As the extrusion ratio and extrusion speed increase, overall DRX bringing grain growth in its train in the -Mg matrix phase decreases the tensile strength of alloys, but the dispersed fiber-shaped LPSO phase remaining in the DRXed grains region makes good the adverse effect of overall DRX followed by grain growth.

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