A New Ultrasound‐Coupled High‐Frequency Induction Sintering System and its Application in High‐Entropy Alloy with High Uniformity and Ultrahigh Hardness

High‐frequency induction sintering has instantaneous heating characteristics, which can reduce the sintering time and inhibit the grain growth. However, due to its nonuniform sintering temperature, it is seldom employed in the sintering of high‐performance materials. The electromagnetic–thermal‐coupled fields in high‐frequency induction heating are analyzed through finite element modeling. The results demonstrate that the skin effect induces a disparity in heating rates between the inner and outer layers of graphite mold, ultimately compromising the uniformity of material properties in the sintered bodies. According to the simulation results, a new ultrasound‐assisted pressure‐coupled high‐frequency induction sintering system is designed and built, and sintering test is carried out with CoCrFeNiMo high‐entropy alloy with poor uniformity. The results indicate that under the conditions of a current intensity of 600 A, electromagnetic frequency of 50 kHz, ultrasonic power of 80%, and constant pressure of 25 MPa, the application of ultrasonic‐assisted pressing significantly enhances the microstructural uniformity of CoCrFeNiMo high‐entropy alloy. Compared to conventional high‐frequency induction sintering, the relative density and Vickers hardness are improved by 12.4% and 37.9%, respectively. In the case of unchanged material composition, the improvement of hardness is due to the improvement of relative density.