Development of High-Strength Nanostructured Magnesium Alloys for Light-Weight Weapon Systems and Vehicles

This final report is written to document briefly the essential discoveries and fundamental understanding we have accomplished over the three-year ARO program. Magnesium alloys are a very attractive type of lightweight materials that have been widely used for Army applications. However, their low strength and poor temperature stability have limited their applications as structural materials. During this three-year ARO program, we have overcome those issues and successfully developed high strength and thermally-stable nanostructured magnesium alloys by accomplished several important milestones: 1) manufacture of high strength nanocrystalline Mg-alloys via cryomilling and spark-plasma-sintering , 2) demonstrate the unveil evidence of nanotwins in nanocrystalline grains that will contribute to enhance the strength, 3) improve the compressive behavior of commercial cast Mg-alloys with a three times higher yield strength (400 MPa), 4) design preliminary extrusion experiments as a secondary process and obtain the highest compressive yield strength (550 MPa) and ultimate strength (580 MPa) reported for Mg-Al alloys, 6) successfully incorporate nanodiamonds as reinforcements into the Mg-matrix giving a 40% improvement in compressive strength, 7) demonstrate that nanodiamonds inhibit the grain growth during processing and services up to 350 C of temperature, which leads to a stable nanocrystalline structure exposed to higher temperatures. The original document contains color images.