AMHERST, Mass. – University of Massachusetts engineer Jae-Hwang Lee has co-authored a research article on cold spray additive manufacturing that seeks to provide a fundamental understanding of the process. Cold spray takes micron-sized particles and accelerates them at supersonic velocities through a specially designed rocket nozzle to strike the surface of a receiving material. The impacting particles undergo extreme plastic deformation and then consolidate, thus forming a dense coating with a near net-shaped quality. The findings are published in the journal Nature Scientific Report.
Lee and the other members of the multi-institutional and multi-disciplinary team of researchers found that aluminum particles that collide with another materials at less than 530 meters per second maintain their distinct spherical shape while at higher velocities, up to 660 meters per second they are more flattened and deformed.
Cold spray can create metal parts with properties comparable to those of wrought metals for certain alloys, such as aluminum. Cold spray can also be used to join dissimilar metals and to repair damaged parts. The process can be used for metals, polymers and other biomaterials.
“In this work,” the researchers say, “collision dynamics and nonlinear material characteristics of aluminum microparticles are investigated through precise single-particle collisions with two distinctive substrates, sapphire and aluminum, across a broad range of collision velocities, from 50 to 1,100 meters per second.”
Thereafter, an empirical constitutive model can be calibrated based on the experimental results and used to investigate the mechanics of particle-deformation history, the researchers say.Real-time and post-impact characterizations, as well as model-based simulations, show that significant material flow occurs during the impact, especially with the sapphire substrate, they say.
“The presented methodology, based on the use of controlled single-particle impact data and constitutive models, provides an innovative approach for the prediction of extreme material behavior,” according to the journal article. “Therefore, materials engineering using the localized extreme mechanical events can allow us an unconventional metallurgical method to precisely control nanoscale morphologies of bulk metals.”
Lee is an assistant professor and the head of the Nano-Engineering Laboratory in the UMass Amherst mechanical and industrial engineering (MIE) department. The authors of the Nature Scientific Report article are Wanting Xie of the UMass MIE and physics departments, Arash Alizadeh-Dehkharghani, Qiyong Chen, and Sinan Müftü of the MIE department at Northeastern University, Victor K. Champagne, director of the ARL Cold Spray Center at the United States Army Research Laboratory at Aberdeen Proving Ground, in Maryland, Xuemei Wang and Aaron T. Nardi of the United Technologies Research Center in East Hartford, Conn., and Steven Kooi of the Institute for Soldier Nanotechnologies at the Massachusetts Institute of Technology.