CAREER: Advancing the Printability of Aluminum Alloys via In-situ Alloying and Hybrid Processing Strategies

This Faculty Early Career Development Program (CAREER) award supports the NSF mission of securing national defense, with the aim of advancing the printability of aluminum (Al) alloys which are utilized heavily in structural applications in the naval and aerospace sectors. Printed aluminum components have the potential to enable increased fuel efficiency and enhance resistance to stress corrosion cracking compared to steel counterparts. Laser powder blown Directed Energy Deposition (L-DED) is a popular metal additive manufacturing (AM) technique due to its capabilities to repair metal components and fabricate large scale parts with high deposition rate. However, only a small percentage of alloys can be reliably manufactured using AM process which hinders widespread industrial deployment of the process. One of the major reasons behind this challenge is solidification cracking. Many high-performance alloys, including aluminum, nickel-based alloys, and refractory alloys, have high cooling rates, thermal gradients and tensile residual stress which contribute to solidification cracking during AM-based processing. The goal of this CAREER project is to first understand the crack initiation and propagation mechanisms in L-DED processed Al and establish new strategies, guided by deposition science and based on laser-material interactions, to resolve these challenges. Major difficulties related to L-DED processing of Al are solidification cracking induced by tensile residual stress, large solidification range and poor aluminum melt fluidity. Research activities will be pursued systematically to reveal the interrelationship between macro-cracks and porosities along with crack nucleation and propagation mechanisms. Strategic ‘in-situ’ alloying efforts will be pursued to advance scientific understanding about the individual effect of select alloying elements that can tune melt fluidity, solidification range and powder flowability synergistically reducing the defects in deposited parts. To address the tensile residual stress challenges, substrate preheating, optimization of scan strategy and laser shock peening (LSP) have been widely used. In this project, inter-layer UIP will be utilized, which is a flexible, cost effective and scalable process that can help induce compressive residual stress and microstructure refinement. Along with novel sample fabrication and characterization plans, high resolution strain mapping using Energy Dispersive Synchrotron X-Ray Diffraction technique will be another major scientific contribution that will identify the effect of thermal gyration of L-DED process on peening affected zone which can impact the microstructure-cracking susceptibility in sub-surface regions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2542988 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Sougata Roy | Institution: Iowa State University, AMES, IA | Award Amount: $550,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2542988 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2542988.html