The limited formability of non-heat treatable 5000 aluminum alloys can be enhanced through warm sheet forming methods. Nevertheless, common heat assisted forming processes, as for example the super plastic forming, do not satisfy the discerning automotive industry due to low cycle times and high costs. A possible approach to overcome the drawbacks of limited ductility and strain rate is the so-called “flash-forming process” (FFP) consisting of a rapid blank heating and a subsequent cold die stamping. Novel in the FFP is the usage of aluminum blanks in a fully work hardened H18 state which allows to manufacture parts with a strength usually achievable only with 6000 aluminum alloys. However, the ductility and damage behavior during this non-isothermal forming process depend upon a number of non-steady state variables which are activated and affected by temperature and deformation. In order to characterize the predominant damage mechanisms a series of uniaxial tensile tests is carried out. By varying the testing temperature between room temperature and 300 °C the influence of crystal lattice recovery and increased diffusion processes on deformation and fracture is investigated. Subsequently, the damage mechanics are qualified by scanning electron microscopy. It is shown that elevated temperatures lead to an altered strain hardening behavior that affects the ductility of the material and leads to an excessive void growth.