Manufacturing Lightweight Structures with Dissimilar Metals
Similar to the development of selectively-reinforced composite materials, REL is developing process techniques to manufacture lightweight structures with dissimilar metals. Also called “bi-metal,” the structure utilizes one metal in a certain region to serve a particular need, and is surrounded or carried by a lower density metal to deliver a lighter-weight structure.
REL uses the squeeze casting process to manufacture a high integrity cast structure that incorporates steel inserts. In addition, REL uses its proprietary thermal barrier technology to coat the inserts to prevent premature solidification and to cast extremely thin walls.
The ultimate goal in bi-metal structures is to achieve complete load transfer across the joint, and this requires a high integrity joint. Without a mechanical feature, the joint as shown is apparent, unfortunately without significant load transfer:
To overcome the lack of a metallurgical bond between dissimilar materials, it’s typical to design with interlocking mechanical features that remain within the cast matrix. The downside of this approach is the thick wall around the features minimizing the weight reduction. REL’s technology and approach will enable thin walls without the quality issues that are common typical process methods.
The applications are primarily focused on efficiencies in transportation, in automobiles, military vehicles and aviation. In an automobile, a frame node made of cast aluminum could incorporate a high strength steel pillar structure. In a combat vehicle, a cast lightweight aluminum structure could incorporate armor steel inserts to protect soldiers.
REL’s work is intended to optimize the performance of bi-metal cast components, developing lightweight structures while minimizing costs associated in manufacturing these joints. REL is under contract with US Army TARDEC to develop a lightweight gun rotor to showcase this technology.