Precipitation hardening behaviour of AA6111

The precipitation hardening behaviour of AA6111 was investigated by: (a) a comprehensive experimental study on the relationship between thermal processing and the evolution of microstructure and properties of the alloy, and (b) integrating the acquired knowledge with the established physical theories and models to develop a new process model to predict the yield strength of the alloy during artificial aging. Two thermal processing histories were examined: (a) artificial aging of the solution treated materials and (b) artificial aging of the materials with variable levels of natural aging. The kinetics of precipitation for the solution treated material was determined using isothermal calorimetry in the temperature range of 160–220°C. A new simple analytical procedure was also introduced to obtain the kinetics of precipitation through a set of differential scanning calorimetry experiments. A new model was proposed to describe the kinetics of concurrent precipitation and dissolution of natural aging zones during artificial aging of the naturally aged materials. The kinetics for the formation of natural aging zones was also modeled. A new process model was developed to predict the yield strength of the alloy during the entire aging process. The validity of the model was verified by the excellent agreement between the predictions of the model and independent experimental results.