In-fire Material Properties of High-strength Aluminium Alloys

Fire is a significant threat to aluminium alloy structures, as they can lose material strength rapidly when exposed to elevated temperatures. To understand the in-fire material response, an experimental investigation on structural high-strength aluminium alloy 7075-T6 at elevated temperatures is presented in this paper. A testing programme including a series of in-fire steady-state and transient-state material tests was carried out on at elevated temperature levels ranging from 20 ℃ to 550 ℃, to obtain the in-fire material responses. The key temperature-dependent material properties, mainly including the stiffness and strengths, were derived from the obtained stress–strain curves and normalised by their room-temperature counterparts, resulting in a set of in-fire retention factors. They were adopted to analyse how elevated temperatures affect the residual stiffness and strengths of high-strength aluminium alloys. The design in-fire retention factors, as specified in the European, American and Chinese design codes, were also evaluated quantitatively and qualitatively based on the test data. The results of the design analyses reveal that the codified retention factors are very inaccurate when used for high-strength aluminium alloys. To address this issue, a set of new predictive models was developed, to provide more accurate predictions of the residual strengths and stiffness of high-strength aluminium alloys in fire.