The phase and structural transformations in equiatomic powder compositions of the Al-Cu-Ni-Fe-Cr system during mechanical alloying (MA), annealing and subsequent spark plasma sintering (SPS) had been studied by X-ray diffraction analysis, scanning and transmission electron microscopy, and differential scanning calorimetry. It has been established that the nanocrystalline high-entropy AlCuNiFeCr alloy synthesized during MA consists of a supersaturated solid solution with a bcc crystalline structure. After annealing and spark plasma sintering at 800 C, the alloy becomes three-phased, and consists mainly of one B2-ordered solid solution, one fcc solid solution (25 wt %), and of the (Сr, Fe) 23 C 6 phase (8 wt %). The Vickers hardness of the sintered AlCuNiFeCr alloy was 8.35 GPa, and the compressive strength at room temperature reached 1960 MPa.
The severe plastic deformation of armco iron by friction is experimentally studied, and the results obtained are used to show that efficient grain refinement is possible in the temperature ranges of warm and hot deformation. A nanocrystalline structure forms only under dynamic recrystallization conditions during hot deformation, which is ensured by deformation in different directions at a rate higher than 10 2 s-1 .
Depth sensing indentation is used to study the effect of grain refinement to submicro and nan ograins on the mechanical properties (hardness, plasticity, Young's modulus) of armco iron subjected to severe plastic deformation by attrition in argon. In contrast to fcc metals, where the hardness increases and the plastic ity decreases as the grain size decreases to 20 nm, the hardness of bcc iron decreases from 5.8 to 3.7 GPa and plasticity δ A increases from 0.82 to 0.87 as the grain size decreases from 50 to 20 nm.
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