Experimental investigation on the post-fire mechanical properties of structural aluminum alloys 6061-T6 and 7075-T73

•Test on specimens of aluminum alloys 6061-T6 and 7075-T73 after fire exposure.•Related post-fire mechanical properties of 6061-T6 and 7075-T73 were obtained.•Mechanical properties significantly changed after exposure to certain temperatures.•The influences of two different cooling methods were considered.•Predictive equations were proposed to evaluate the post-fire mechanical properties.

Aluminum alloys are increasingly used in engineering structures. During fire hazards, aluminum alloy structures are inevitably exposed to elevated temperatures. Provided structural collapse does not occur after a fire, a reliable evaluation of the residual performances of the structures is needed to decide whether the structures should be dismantled, repaired, or directly reused. Therefore, an experimental investigation was conducted to reveal the post-fire mechanical properties of two widely used structural aluminum alloys, namely, 6061-T6 and 7075-T73. Specimens were initially heated to nine various pre-selected temperatures up to 550 °C and subsequently cooled down to ambient temperature by two different methods: air cooling and water cooling. Tensile coupon tests were performed on the specimens until fracture, and the post-fire stress–strain curves, elastic modulus, yield strength, ultimate strength, and ductility were obtained. The mechanical properties of 6061-T6 were dramatically reduced after exposure to temperatures exceeding 300 °C. For 7075-T73, the corresponding temperature was 200 °C. The post-fire mechanical properties were obviously influenced by cooling methods, particularly after cooling from a relatively high fire temperature. New predictive equations, where the influences of different cooling methods were incorporated, were proposed to evaluate the post-fire mechanical properties of the aluminum alloys 6061-T6 and 7075-T73. The results presented in this study are expected to lead to an accurate assessment of the post-fire performances of aluminum alloy structures.