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摘要
Al15Cr15Fe50Ni20-xBx (x = 0, 2, 4, 5, 6 and 8; x values in molar ratio) high-entropy alloys were prepared by vacuum arc melting, and the effects of B content on the microstructures and mechanical properties of Al15Cr15Fe50Ni20-xBx high-entropy alloys were systematically studied. The results showed that the Al15Cr15Fe50Ni20 high-entropy alloy was composed of FCC and BCC phases. With the addition of B, boride phases could be observed in the studied alloys. Moreover, lattice distortion was formed according to theoretical calculations. When the content of B was 2, 4 or 5, the studied alloys showed a typical hypoeutectic structure. When the content of B increased to 6 or 8, a hypereutectic structure could be observed. With increasing B content, the fracture strength and hardness values of the Al15Cr15Fe50Ni20-xBx high-entropy alloys showed a trend of first increasing and then decreasing. The Al15Cr15Fe50Ni15B5 high-entropy alloy had the best comprehensive mechanical properties, with a hardness of 575 HV, fracture strength of 2595 MPa and compression rate of 31%. The main strengthening mechanisms of the studied alloys were fine grain strengthening, second phase strengthening and solid solution strengthening. By combining theoretical statistics and experimental results, B-containing high-entropy alloys were found to be composed of FCC + BCC + boride phases when the following criteria were met: - 17.12(kJ/mol) <= Delta H-mix <= - 10.11(kJ/mol), 5.64 (%) <= delta r <= 11.02 (%) and 1.11 <= Omega <= 1.47.
