• Increasing Al content in AlxCrFe3Ni medium entropy alloys increases BCC phase fraction and decreases FCC phase fraction, enabling microstructural tuning.
• The Al0.54CrFe3Ni alloy achieves an exceptional damping capacity (internal friction Q-1 = 0.059), outperforming most FeCr damping alloys.
• The unique microstructure of hard BCC matrix surrounded by soft FCC phase hinders vibration wave propagation, enhancing damping.
• The Al0.54CrFe3Ni alloy also exhibits high yield strength (811.16 MPa), offering a promising combination of damping and mechanical properties.