GOALI/Collaborative Research: Fundamental Research on Impact Welding of Aluminum and Steel

Ohio State University, The, Columbus OH

Investigators

Abstract

This Grant Opportunity for Academic Liaison with Industry (GOALI) collaborative research award supports fundamental research on an emerging welding technology - impact welding - to join material combinations that are otherwise difficult to join. Research will focus on aluminum-steel welds because there are diverse and important commercial needs in joining these metals. Both base metals are well characterized and the development of robust aluminum-steel unions can reduce automobile mass. Lighter cars use less fuel and emit less carbon to the atmosphere. Research results will enable wider application of this technology in important industries including automotive, aerospace, and medical devices. Traditional welding processes melt both metals to be joined and the molten mixing can result in brittle intermetallic compounds, rendering the joints unsuitable for most structural applications. Impact welds can be strong and tough and are created in the solid state by a high-speed (typically 200-700 m/s) oblique collision between two metal surfaces. The objectives of this research are: 1) to understand how the thickness of the flyer plate (and therefore its total kinetic energy) affects the structure of the interface that is formed, 2) to understand the real-time evolution of strain, temperature and morphology of the interface during the impact welding process and 3) relate the deformation history to the final structure and properties of the weld. Unique tools are used to study aluminum-steel impacts from flyer thicknesses of 25 µm to 25 mm. Laser impact welding and explosive welding are used for the thinnest and thickest flyers, respectively, while vaporizing foil actuator welding will be used to accelerate flyers of several intermediate thicknesses. Photonic Doppler velocimetry will enable detailed measurements of collision speed and angle. Finite element models based on Smoothed Particle Hydrodynamics and Arbitrary Lagrangian-Eulerian methods will be developed for these problems. Their validity will be tested by metallographic examination of welded structures and comparison of these to simulation. These models will be used to understand the complex dynamic development of material strains, temperatures and structures and on a wide range of length scales.