Laser-powder bed fusion printed CrMnFeCoNi high entropy alloys engineered for acoustic insulation

Metallic materials are generally efficient sound conductors, posing challenges for applications requiring acoustic insulation. Traditional methods, such as drilling arrays of holes, compromise structural integrity and mechanical performance. This study introduces an approach utilizing laser powder bed fusion (LPBF)-printed CrMnFeCoNi high entropy alloy (HEA) samples with optimized intrinsic internal voids during manufacturing to achieve broadband acoustic insulation. Utilizing the inherent voids in LPBF-fabricated HEAs makes it possible to achieve effective sound attenuation through Anderson localization without additional damping materials or compromising mechanical integrity. Numerical simulations reveal pronounced wave localization effects induced by random backscattering, resulting in an exponential decay of sound propagation. Experimental validation demonstrates that LPBF-fabricated HEA samples exhibit superior sound insulation, achieving an average sound transmission reduction of -65 dB over a 10 mm sample thickness with respect to lossless water medium. Remarkably, even with a defect fraction exceeding 25%, these samples retain hardness values approximately 10% higher than stainless steel 316.