Improved metals applied to marine vehicle.

• Author: Pappalardo, Joe

A process using advanced nano-science in metal processing may provide the material for a tough, lightweight Marine expeditionary vehicle, Navy researchers predict.

The process known as cryomilling is adding properties to aluminum that may be used to forge a craft with the toughness and low weight required by the Marine Corps, according to Rodney Peterson, project manager with the Naval Surface Warfare Center in Carderock, Md.

The blue-sky hope, Peterson told the audience at a recent conference, is to design "a 30-ton tank to replace a 70-ton tank" for the Marines.

The Carderock Division is contributing to the development of a future U.S. Marine Corps family of vehicles, referred to as the Marine Air-Ground Task Force Expeditionary Family of Fighting Vehicles (MEFFV). Navy technical experts are managing an advanced materials development program that is generating lightweight structures and technologies to meet the Corps' needs.

The MEFFV will replace the M1A1 Abrams tank and the light armored vehicle by 2020. This effort started in 2002 and is halfway through the development process, Peterson said.

Metals are not monolithic slabs of material, but are composed of individual grains of similar composition with differing crystalline orientations. In general, smaller grain size means greater strength. Cryomilling takes the concept several steps further.

Navy scientists are changing standard aluminum (AL 5083) by introducing grains of aluminum so small that the material's properties change. Doing this requires grinding, or milling, the aluminum powder in extremely cool temperatures that is obtained by exposure to liquid nitrogen. The process encourages the formation of nano-scale aluminum oxide and nitride particles, which makes materials stronger, as well as stabilizing their microscopic orientation and structure.

Initial tests at Carderock...