A Method of Controlling Shock Induced Damage in Aluminum Alloys,

In the design of armor to protect a vehicle, suppression of behind the armor fragments spall resistance can have significant influence on mission survivability. It is shown that, once a microscopic mechanism is postualted for the occurence of spall fracture, it is possible to tailor the response of a material to suppress the spall fracture process. Al-4 12 wt. Cu was selected as the material for testing. By selection of suitable heat treatments prior to shock-loading a variety of homogeneous precipitate distributions with differing potential as vacancy getters may be obtained. The alloy, fabricated as Instron tensile specimens and shock loading specimens, was heat treated to three conditions designated under-, critical- and over-aged. The experiments to-date indicate that a Vacancies are significant to the nucleation of porosity damage during shock loading as evidence by strong precipitate growth in the under-aged alloys. b At the shock strengths examined the potential for vacancy gettering action is more important to suppressing damage than are yield strength, ultimate strength, work handening rate or ductility as shown by comparison of the results of the under-, over-, and critical-aged alloys.