Ultrasonic-vibration-enhanced plasticity of an entropic alloy at room temperature

Deformation at a high-strain rate and low stress is of great significance for the emerging entropic alloys. However, this deformation process is generally achieved under heating or cryogenic conditions to ensure a good plasticity. Here, we demonstrate a facile route to enhance the plasticity of entropic alloys at ambient temperature. Assisted by ultrasonic vibration at a frequency of 20,000 Hz, the compression strain of the Al ₈₀Li ₅Mg ₅Zn ₅Cu ₅ entropic alloy increases from 17% under conventional compression to 30% within 1 s, while the applied stress is less than 100 MPa, only 1/6 of the compressive strength. In contrast to conventional compression, the ultrasonic loading achieves a high-instantaneous strain rate up to 10 ³ s ⁻¹ and high-frequency cyclic loading. This loading mode results in reflected stress waves and stress-relief effects in the deformation areas, thus causing the dislocations diffusion in face-centered-cubic (FCC) phases as well as the refinement and dispersion of intermetallic phases in the entropic alloy. These distinct microstructural evolutions synchronously suppress dislocations pile-up, and facilitate the grains rotation and sub-grains formation, which significantly decrease the deformation stresses, accommodate higher plastic strains, and eliminate deformation textures. Our studies discover a novel deformation mechanism for the entropic alloy that can offer a versatile approach of rapid structure forming.