Firefighter Ladders Made of AA6063 Alloy Exposed to Elevated Temperatures and its Influence onto Mechanical Properties

The firefighting ladders belong to essential tools used by members of the Fire Rescue Service of the Czech Republic. In the past, wooden ladders were used although their applicability and duration were strongly limited. Formerly used wooden ladders were then replaced with steel-made. However, the weight of such ladders caused big problems during the firefighting and therefore an aluminium ladders made of AA 6063 alloy are nowadays used. The ladders are however susceptible to thermal effects during firefighting and may reduce its mechanical properties. The present paper reports the microstructural change of two different ladders both made of AA 6063 alloy when annealed at different temperatures and duration. Both the ladders showed almost similar behaviour reaching the highest decrease in theirs TYS and UTS when exposed to a temperature of 400 °C reducing its initial TYS of 229 MPa for ladder no.1 and 237 MPa for ladder no.2 down to 71 MPa and 81 MPa, respectively.