Optimization of heat treatment in cold-drawn 6063 aluminium tubes

The effect of heat treatment condition on mechanical properties and bendability of 6063 aluminium cold-drawn tubes was investigated. The standardized heat treatment presently used in manufacturing of cold-drawn tubes increases the cost and time of the process which ultimately reduces plant productivity. The effects of time, temperature, and furnace heating rate were studied in order to identify an optimized heat treatment for tubes with different cold work levels. Drawn from the as-extruded state, tubes were heat treated to under-aged, peak-aged, and over-aged conditions with time and temperature ranging from 1 min to 24 h and 130–200 °C, respectively. Mechanical properties were determined with full section tensile tests whereas tube bendability was evaluated on an industrial draw bending machine. These characteristics were evaluated in each condition in order to identify the heat treatment which allows conforming to 6063-T832 temper requirements and gives sufficient bendability. Moreover, bendability was successfully correlated to fracture strain measured during a uniaxial tensile test and a threshold value over which problem-free bending operation was determined.