The Army Research Laboratory (ARL) conducted a long time on the performance and dimensions of the armored vehicle's side and front armor alloys and a series of simulated live-fire experiments to select the two best-performing aluminum alloys. The strength, the anti-ballistic explosiveness, the bullet-resistant breakdown resistance and the corrosion resistance are well combined, and the formability is also obtained by the intermediate heat treatment. These two alloys are 2139 and 7056 alloys that have been used in the aerospace industry. The armor plates are manufactured by Constellinm, and their registrars are branded Keikor 2139TM and Keikor 7056TM.
Keikor 2139 alloy is a structural alloy developed for the aerospace industry. It has high strength and fracture toughness. It is an aluminum alloy with excellent comprehensive performance. It has undergone a series of standardized gun test and field test in the US Army Research Laboratory for a long time. It is also considered to be a good armored aluminum alloy. In addition to qualified anti-ballistic properties, it also has good corrosion resistance and heat resistance. It does not soften at higher temperatures. For armored vehicles, it is highly resistant. Corrosion is also an important technical indicator because it operates and operates in extremely severe and complex environments. It is commendable that the 2139 alloy has very low stress corrosion sensitivity.
2139 alloy is an Al-Cu-Mg-Mn-Ag alloy with low impurity content. As of December 2016, 535 of the commonly used alloy alloys (Active alloy) registered with Alcoa, the alloy type (inactive) Alloys) 158, a total of 693, plus the aluminum companies have characteristics are not registered, it is estimated that the deformation of the aluminum alloy model is about 1000. There are 18 silver-containing alloys in the 693 alloy models, including 16 of the 2XXX series, 2 of the 7XXX series (7009 alloy, 7047 alloy), and the maximum silver content is 0.7%. The solid solubility of Ag in aluminum can reach 55.6% at 566 °C, and then it changes drastically with the decrease of temperature. Adding (0.1%-0.7%) Ag to 2XXX series and 7XXX series can improve their mechanics. Performance and resistance to stress corrosion cracking, 2139 alloy contains 0.15% Ag - 0.6% Ag. Ag can form an Ag2Al compound (γ phase) with Al at 727 ° C, which contains 88.9% Ag, dense hexagonal lattice.
The earliest used for armor plate was the 2519-T87 alloy thick plate, which was later found to have high stress corrosion cracking sensitivity and was eliminated because it is not suitable for combat under complex conditions. The composition (% by mass) of the 2139 alloy is as follows: Si 0.10, Fe 0.15, Cu (4.5 - 5.5), Mn (0.20 - 0.60), Mg (0.20 - 0.80), Cr 0.005, Zn 0.25, Ti 0.15, V 0.05, Ag (0.15 - 0.60), other impurities a single 0.05, a total of 0.15, the rest is Al.
According to the US military material standard MIL-DTL32341A, the minimum mechanical properties of the 2139 alloy are shown in the table below. It is known from the composition of 2139 alloy that it is an alloy with a very low impurity content, so it has high fracture toughness and fatigue resistance, and the damage resistance is also good.
The Keikor 2139 alloy slab has two states: AP/FSP (US Patent/Federal Patent) anti-shooting level, ie T8 state. The production process in the former state is to perform artificial aging after appropriate cold working rate, that is, to perform cold working and then artificial aging after solution treatment, so that it has good comprehensive performance and is used for manufacturing the side deck and the top deck of the armored vehicle. The production process of the T81 state thick plate is that after the solution treatment, the deformation is slightly processed by about 1%, so that the strength is slightly improved, and then artificial aging is performed. The armored vehicles made of 2139-T81 alloy thick plates have stronger protection performance. That is to say, when the armored vehicles are protected, the 2139-T81 alloy armored vehicles are much lighter, with higher operational flexibility and faster speed.
Research by the US Army Research Laboratory shows that 2139 alloy plates can withstand 2110 ft/s shots when the thickness of the armor plate is equal, while the safety shot speeds of the 5083-H131 alloy and the 7039-T64 alloy plate are 1780 ft/s, respectively. 1910ft/s.
The antiknock performance of Keikor 2139 alloy is generally superior to traditional alloys, especially 2139-T84 alloy. Because T84 state plate has higher tensile strength and fracture toughness, they are well combined. In the standard blasting test, its plastic deformation is much smaller than that of the 5083-H131 alloy slab. The permanent deformation of the 2139-T84 alloy thick plate is about 50% smaller than that of the 5083-H131 alloy. Therefore, when the explosion occurs on the battlefield, the impact of the 2139-T84 alloy armored vehicle will be significantly reduced, which can greatly reduce the potential damage.
The anti-explosive state plate (T84) is usually used as the lower deck of the armored vehicle. The plates are artificially aged and the aging temperature is quite high, resulting in excellent formability. The 2139-T84 alloy armor plate is also subjected to a patented intermediate solution treatment. This sheet has both high strength properties and good formability, and the stress in the molded part is low, which is very advantageous for subsequent processing.
In the manufacture of armored vehicles, the structural strength of the plates will be reduced, whether it is welded or screwed. For this reason, Kenli Aluminium has successfully developed a series of 2138-T84 alloy wire, which is welded with the structural weld strength and The matrix strength is almost equal and the welding thermal stress is also lowest. The Keikor 2139-T84 alloy armor plate is produced by Kennedy Aluminium's Revenswood (WV) rolling mill in West Virginia. Its high-end materials such as aerospace are its leading products.
After extensive laboratory tests and field live-fire exercises in the US Army Research Laboratory, the 2139-T84 alloy anti-piercing projectile and explosive shrapnel are superior to the traditional 5083-H131 and 7039-T6 alloy thick plates, which has been obtained by the Army Research Laboratory. Certification. The United States has used the Keikor 2139-T84 alloy plate to manufacture a new generation of advanced CAMEL (Concept for Advanced Mititary Explosion-Mitigating Land). The car is manufactured by Pratt & Miller of Detroit, USA, and is fully evaluated and field-run by the Army's Tank Automotive Resarch Development and Engineering Center (TARDEC). All indicators of aluminum alloy armored vehicles are qualified and perform well. The work was also supported by the Combat Vehicle Prototype (CVP).