Aluminum Alloys in Military Vehicles and Equipment

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Historical Development of Military Aluminum Applications

The military adoption of aluminum began in the late 19th century with innovative applications that demonstrated the material's potential for defense applications. The French Government pioneered military aluminum use by ordering aluminum torpedo boats in 1892, recognizing the strategic advantages of lightweight naval vessels. The United States Army followed this trend by acquiring aluminum picket pins, tent pins, and canteens in 1896, with President Theodore Roosevelt famously carrying an aluminum canteen during the charge up San Juan Hill in the Spanish-American War.

During the 1890s, the United States Navy procured 94-inch-wide aluminum sheets for large naval assemblies, possibly including ship superstructures. This early adoption established aluminum as a viable military material, setting the foundation for expanded applications in subsequent conflicts.

The First World War generated urgent demands for aluminum across multiple military applications. Germany, confronting critical shortages in iron and steel, strategically employed aluminum in army tanks and industrial machinery, demonstrating aluminum's capability to substitute for traditional materials under resource constraints.

The Second World War significantly expanded aluminum's military applications, particularly in naval structural components, functional equipment, and personnel gear aboard fighting ships. Notable military adaptations during this period included aluminum bridges and pontoons, walkie-talkie communication sets, fuel drums designed for air transport, aircraft landing mats, and high-intensity searchlights.

Military Aluminum Armor Systems

Military combat vehicle requirements establish stringent specifications for armor protection, with aluminum alloys meeting these demanding criteria while providing weight advantages. The 5xxx series strain-hardenable aluminum alloys have been utilized in all aluminum military vehicles produced to date, offering proven ballistic performance. The ballistic merit of these alloys relative to rolled homogeneous steel armor varies significantly with impact angle, making alloy selection critical for optimal protection.

The 7xxx series heat-treatable aluminum alloys provide enhanced protection at all impact angles, representing advanced armor technology. Since minimum weight for a given protection level is essential for vehicle mobility, aluminum armor systems are extensively used in modern combat vehicles.

Armor material selection depends on multiple requirements beyond ballistic criteria. For vehicular applications, weldability represents a primary necessity because welding most economically produces the structural integrity and watertightness required for amphibious operations. Satisfactory machinability and formability are essential for efficient shop fabrication processes.

Armor strength must adequately resist service stresses, including severe shocks encountered during airdrops and cross-country operations. Completed vehicles may operate or remain stored for extended periods under extreme temperature conditions (-80 to 165°F) and high humidity environments. Military operations also include movements through corrosive saltwater environments, requiring armor materials that retain mechanical and ballistic properties while resisting corrosion under such demanding conditions.

Aluminum alloy armor provides additional advantages over steel, including freedom from low-temperature embrittlement and greater structural rigidity resulting from thicker sections for equivalent protection levels. This increased rigidity, up to nine times that of steel, typically eliminates the need for secondary structural support systems.

Production forms of aluminum alloy armor include rolled plate, extrusions, and forgings. For alloys with ballistic properties developed through strain hardening, primary use occurs in rolled plate form. Heat-treatable aluminum alloys that can be effectively welded are being developed as weldable armor systems, enabling greater use of forged and extruded armor components. Cast aluminum armor components are being introduced for applications where requirements other than ballistic performance dictate section thicknesses greater than those necessary for wrought armor.

Military Vehicle Applications

Wheeled Military Vehicles

Aluminum's dramatically increased use in military vehicles over recent decades results from requirements for reduced weight to improve vehicle mobility, amphibious capability, air transportability, increased payload capacity, and simplified maintenance procedures. Many successful, economical commercial highway vehicles of aluminum construction have been adopted by military services. However, most combat and tactical vehicles have no civilian equivalents, requiring aluminum components developed specifically for military service.

Wheeled vehicles for general-purpose duty are used predominantly for logistics operations, including support and supply functions. Aluminum 5xxx series alloy sheet and 6061-T6 and 6063-T5 extrusions are employed extensively in large bus bodies, cargo trailers, liquid-transport tanks, and comparable vehicles. Bus and cargo-trailer bodies typically utilize riveted assemblies of aluminum sheet and extrusions, while tankers employ welded 5xxx series alloy sheet assemblies. Tanker pumps, filters, and plumbing systems are manufactured from aluminum castings and tubing.

Special-purpose wheeled vehicles possess standard military functions or characteristics outside normal commercial requirements. The Minuteman missile transporter exemplifies single-purpose highway vehicles with extensive aluminum applications.Its aluminum components include 2024-T6 alloy forged disk wheels, 2014-T6 forged front hubs, fifth-wheel control arms and cross braces, and equalizer beams in tandem axle assemblies. Additional components include 6061-T6 plate and bar stock weldments in trailer-frame cross-assembly rear hinge structures and suspension system brackets, 220-T4 alloy sand-cast support brackets for auxiliary transmission and gasoline tanks, welded 5052 sheet gasoline tanks, and 1100 alloy brazed tube-and-fin radiators.

Specialized Combat Vehicles

The M-102 trail-gun-type 105-mm howitzer represents a lightweight weapon carriage designed for rough terrain operations, fabricated almost entirely from aluminum alloys. Fusion welded box sections of 5086-H32 sheet and 5086-H112 extrusions provide structural efficiency and minimal weight in trail, body, and base assemblies. Functional extruded tubes, including those in cradle structures, utilize 5086-H32 alloy. Forged 7075-T6 and 7079-T6 structural brackets support trunnion and cradle systems, while ground stakes are 7075-T6 forgings with hard anodized surfaces for abrasion resistance. Wheel hubs are manufactured from A356-T61 castings.

With a gross weight of approximately 1.6 tons, the M-102 represents the lightest 105-mm conventional gun design achieved. Helicopter transport for maximum tactical effectiveness takes exceptional advantage of its lightweight construction.

The lightweight truck family, including XM-561, XM-410, and XM-656 models, replaced traditional designs with capacities ranging from 1.25 to 5 tons. Combined objectives of cross-country capability and lightness for maximum mobility and air transportability demand highly efficient structural design approaches.

Tracked and Amphibious Vehicles

The M-116 general-purpose tracked logistics vehicle represents lightweight design at 5.5 tons, constructed principally from 5086-H34 sheet on extruded aluminum frames, joined through welding, riveting, and bolting. Its drawn 2024-T4 plate wheels and 6062-T6 extruded clamping plates on track bands characterize current lightweight tracked vehicle designs.

Amphibious vehicles of aluminum construction include the Army LARC (lighter, amphibious, resupply, cargo) group and Navy LVH (landing vehicle, hydrofoil), both representing general-utility craft for ship-to-shore operations. The Army MFAB tactical bridge and ferry system also utilizes aluminum construction.

The Navy LVH represents a cargo or general-utility hydrofoil boat equipped with wheels, differing from LARC vehicles through retractable wheels, foils, and propeller systems. High-speed and efficient performance are achieved through sophisticated structural and hydrodynamic design with extensive aluminum utilization. Sheet, plate, and extrusions of 5083 alloy in H112 and H113 tempers are welded to form stressed-skin hull and superstructure assemblies.

Military Ordnance Applications

Ammunition Systems

Lower costs and equal or superior performance have led to increasing aluminum use in recent years for projectile components, including both cartridge-launched and rocket-launched systems, cartridges, mines, bombs, and their associated components.

The smallest projectiles employing aluminum include several varieties of conventional 20-mm rounds featuring conical aluminum nosepieces machined from 2024-T4 rod or bar stock. Two 40-mm projectile models incorporate machined tubular skirts of 6061-T4 alloy. Aluminum components forged to precise dimensions represent economical solutions for mass-produced ammunition items.

Weapons and Launch Systems

Aluminum utilization in guns and launchers ranges from M-16 rifles to superstructure components of M-474 systems used for transporting Pershing system equipment. One M-16 model with 5.56-mm bore incorporates forged 7075-T6 upper and lower receivers plus several smaller aluminum parts. The M-14 standard automatic rifle employs a 7075-T6 buttplate assembly for light weight and capacity to accept durable anodic coatings.

The M-72 recoilless rocket launcher LAW (light antitank weapon) features a 6061-T6 impact extruded chamber. As a variation of the World War II "Bazooka," it is carried complete with its rocket, fired once, and discarded, making low cost essential. An aluminum impact extrusion utilized as part of the shipping container and firing barrel contributes significantly to low cost while maintaining maximum weight below 4.5 pounds.

Naval Weapons Systems

Naval Weapons Systems Torpedoes commonly undergo several practice firings during service lives and are designed with slight net positive buoyancy for floating and recovery after practice runs. Weight reduction in torpedo shells or machinery allows additional instrumentation or payload capacity. Aluminum is employed extensively for weight reduction in Mark 37, 44, 45, 46, and 48 torpedoes, with aluminum-silicon alloy castings used frequently for major components including outer casings, propellers, and shroud rings.

Additional Military Equipment Applications

Bridge Systems

Military bridges represent typical applications making extensive use of aluminum alloys. A pontoon bridge system designed during World War II and still in production utilizes primarily 2014-T6 alloy extrusions. Assembly involves considerable welding, particularly along neutral axes of tubular beams manufactured from extruded channels where upper webs form roadway surfaces. Roadway faces feature longitudinal extruded and transverse press-formed depressions to improve vehicle traction.

The armored vehicle-launched (AVL) bridge illustrates increasing mobility in military bridging systems. This aluminum and steel structure attaches to modified tank fronts, folds to ride atop vehicles, and operates hydraulically without exposing personnel. Aluminum's superior strength-to-weight and stiffness-to-weight ratios contribute significantly toward maximum portability and operational mobility.

Electronic Hardware Systems

Electronic hardware applications demonstrate aluminum's versatility in military equipment beyond structural components. Various communication systems, radar equipment, and electronic warfare devices utilize aluminum alloys for housings, heat sinks, and structural frameworks, taking advantage of aluminum's electrical conductivity, thermal management properties, and electromagnetic shielding capabilities.

Conclusion

Aluminum alloys have fundamentally transformed military vehicle design and equipment manufacturing since their introduction over a century ago. The continued evolution of aluminum alloy technology, including advanced heat treatments, specialized forming processes, and innovative joining techniques, ensures aluminum's continued prominence in military applications. Modern military requirements for enhanced mobility, reduced logistical burden, and improved performance characteristics align perfectly with aluminum's inherent advantages, positioning these materials as essential components in future military system development.