Ultrasonic characterization of cellular metal structures

A new class of cellular materials synthesized by partially consolidating hollow metal powders has been gaining interest for multi-functional applications (where load support combined with other functionalities such as acoustic damping, thermal insulation or energy storage is required). These functionalities depend upon the volume fraction of porosity, type (open/closed) and pore size. The independent controllable pore volume fraction, pore size and fraction of open and closed porosity of these structures offers the possibility of tailoring a structures properties to specific applications. Here, the elastic stiffness and acoustic attenuation of highly porous structures made from hollow gas atomized superalloy spheres have been measured. The Youngʹs and elastic shear moduli were deduced from ultrasonic wave velocities while the acoustic attenuation was evaluated from the temporal decay of laser induced standing acoustic waves. The elastic stiffness of these structures varied with the pore volume fraction and the acoustic attenuation scaled with the pore volume fraction and size. The unique attributes of these hollow powder cellular structures offer the potential to tailor their properties for individual applications thereby exploiting the multi-functional nature of these structures.