damping performance and strain rate sensitivity of multi-phase high entropy alloy

The development of heterogeneous high entropy alloys (heas) has seen notable advancements in recent years. this progress is attributed to the ability to finely adjust the mechanical characteristics through the utilization of complex microstructures comprising multiple phases and various deformation mechanisms. heas may experience demanding external forces that lead to varying strain rates and vibration frequencies. consequently, the microstructure of the alloy can exhibit distinct mechanical and damping responses. since damping behavior is a critical material property, it has attracted considerable attention, especially within industrial applications where the control of vibrations is a primary concern. this work presents the effects of the sigma phase and the level of recrystallization on the damping properties over a wide temperature range and work hardening under various strain rates of a heterogeneous hea with fcc-bcc phases. under applied stress, besides dislocation slip, the transformation-induced plasticity (trip) mechanism can enhance mechanical behavior by improving the strain hardening rate (shr). the shr levels exhibit variations depending on the applied strain rate, reflecting different trends based on the underlying microstructural characteristics. by employing various thermomechanical processes in the examination of trip-assisted hea, strain rate sensitivity (srs) becomes a valuable indicator of how the microstructure evolves during yielding. the results obtained indicate that the yield strength (ys) of the trip-assisted hea remains relatively consistent when modifying the strain rate values. however, the ultimate tensile strength (uts) values exhibit sensitivity to the strain rate, indicating srs within the alloy system. the damping behavior is affected by the grain size such that the as-received sample shows a higher internal friction value. on the contrary, even though the sample annealed at 850°c has coarser grains compared to the 750°c sample, it exhibits a lower damping capacity. this is associated with the presence of the sigma phase in the microstructure, which can affect the mobility of the domains and restrict the movement of defects. in conclusion, changes in srs and damping performance are influenced by several factors, including grain size, degree of recrystallization due to applied thermomechanical processes, trip mechanism, and the presence of brittle phases such as the sigma phase within the microstructure of the hea. damping properties were studied using a dynamic mechanical analyzer (dma) within a temperature range from 60°c to 500°c with a heating rate of 5°c/min. three distinct strain rates were applied during monotonic mechanical tests conducted at room temperature. all conclusions are evidenced by a multitude of characterization techniques such as transmission electron microscopy (tem), x-ray diffraction (xrd), and scanning electron microscopy with electron backscatter diffraction (sem-ebsd).