NSF-Europe: The Mechanisms of Grain Refinement in HCP Metals and Alloys with Severe Plastic Deformation Leading to Nanoscale Microstructures

University Of Southern California, Los Angeles CA

Investigators

Abstract

This grant supports a collaborative research program between the University of Southern California (USC) and the Consejo Superior de Investigaciones Cientificas (CSIC) Centro Nacional de Investigaciones Metalurgicas (CENIM), on Madrid, Spain. CENIM has received a three-year grant from the Spanish Ministry of Science and Technology for "Optimization of the Mechanical Behavior of Light Al and Mg Based alloys for the Transportation Industry by Severe Plastic Deformation." The NSF grant provides funding for USC in a complementary area to the Spanish grant. The Spanish research explores severe plastic deformation using rolling of Ti and Zr alloys as a means to produce nanoscale grain-size alloys. Their objective is to create a new class of economical high-strength, light alloys. The US team looks at pure light metals that are a basis for the alloys studied at CENIM. Two essential aspects addressed by the study at USC are (a) the characterization of the evolution of microstructure of light HCP metals and Al single crystals during intense plastic deformation in tension, equal-channel angular pressing, and rolling leading to the formation of a nanocrystalline structure and (b) dynamic restoration mechanisms leading to the nanostructure. The former delineates a specific issue that has not been sufficiently addressed by the scientific community for HCP metals and for single crystals of any structure. The technical community has been empirical in its quest to produce very fine-grain alloys of commercial value. The basic USC effort underpins the adhesive roll-bonding technique centered in Madrid. Adhesive roll-bonding is a technique that may improve present capability to create submicron microstructures by increasing the fraction of subgrain boundary facets that become high angle boundaries and could result in reduced processing costs as compared to equal-channel angular pressing. A primary objective of the grant is student participation in this international program. The program will look for graduate students from underrepresented groups. Graduate students, postdoctoral scholars, and faculty will participate in exchanges on a long-term basis (three months to two years) between the institutions. The collaborative program is complementary in scope, synergistic and, due to a past record of collaboration, highly likely to succeed. Dr. Maria-Teresa Perez-Prado of CENIM and also a Research Assistant Professor at USC is a vital participant in this project. Undergraduates will participate in the program both in the summer and as part of a formal Senior Project. This research will be integrated into the USC Aerospace and Mechanical Engineering courses, AME 560, Fracture and Fatigue of Materials. An additional broad impact feature is the potential for developing an inexpensive and versatile metal-forming technique to produce high strength and high toughness nanoscale light alloys.