Density Analysis of Additive Manufactured Metal Parts Using Laser Ultrasonics

Selective laser melting (SLM) technology can be used to rapidly form metal parts of any structure, but the structural properties of the manufactured parts are different from those of traditional metal parts. This paper investigates the ultrasonic characteristics of the Additive Manufactured metal parts produced by Selective Laser Melting (SLM) technology and studies the relation between the metal density and the longitudinal wave velocity in different forming directions. An experiment has been carried out by using a pulsed laser to induce ultrasonic waves in additive manufactured 316L stainless steel parts. The experimental results show that the longitudinal wave velocity in different forming directions is strongly correlated with the metal density. The samples with higher densities have more similar velocity in different forming directions, and hence are more isotropic. The relation between the metal density and the ultrasound velocity has been found by fitting the experimental data into a quadratic curve. The results of this work can be potentially used for evaluating the density of the additive manufactured metals and hence evaluating the physical properties by measuring its ultrasound velocity.