A new single crystal high entropy alloy is developed and produced using Bridgman directional-solidification and seed-crystal method. The microstructure exhibits the directional dendrite morphology and is mainly composed of the FCC matrix and the L1₂ ordered precipitates. Its high-temperature yield strengths are far higher than those of the first-generation single crystal superalloys, and close to those of the second- generation ones. The solid-solution strengthening effect from the high content of W and Mo, as well as the precipitation strengthening effect from the combined addition of Al, Ti, Ta, and Nb, should be responsible for the excellent high-temperature strength of the investigated alloy.

The paper presents and analyzes the results of experimental tests performed on two non-alloy low carbon steels (1.1141 and 1.0122) in cases of their exposure to impact fracture energy and uniaxial high cyclic mechanical stress-controlled fatigue. The experimental results provide insight into the changes in the Charpy impact fracture energy of the V-notched test specimen that occur as a result of temperature changes. The experimental results also provide insight into the mechanical response of the tested materials to mechanical uniaxial high-cycle fatigue at room temperature in an air atmosphere and at different applied stress ratios. Material fatigue tests refer to symmetric (R = −1), asymmetric (R = −0.5) and pulsating tensile (R = 0) cycles. The test results are shown in the S–N diagrams and refer to the highest applied stresses in relation to the number of failures at a given stress ratio. Using the modified staircase method, the fatigue limit (endurance limit) was calculated for both tested materials at each prescribed stress ratio. For both tested steel alloys, and at prescribed stress ratios, the fatigue limit levels (σ_f) are shown as follows: for steel C15E+C (1.1141)$\to {\sigma }_f\left[{250.8}_{R=-1};{345.4}_{R=-0.5};{527}_{R=0}\right]\left(\mathrm{MPa}\right);$ and for steel S235JRC+C (1.0122)$\to$${\sigma }_f$[${202}_{R=-1};{310}_{R=-0.5};{462}_{R=0}]\left(\mathrm{MPa}\right)$. All uniaxial fatigue tests were performed on unnotched, smooth, highly-polished specimens. The microhardness of both materials was also tested.