Analysis of precipitation, dissolution and incipient melting of Al2Cu in B206 Al alloy using in-situ neutron diffraction

The B206 Al alloy is a commonly used automotive alloy for powertrain, suspension and chassis components. Heat treatment is an important post-casting process used to improve the mechanical properties of cast components. Improvement of the heat treatment process requires a better understanding of phase evolution of Al2Cu as a function of temperature. In this study, a novel application of in-situ neutron diffraction was used to examine precipitation, dissolution and incipient melting characteristics of Al2Cu as a function of temperature during sample heating. Additional experiments, where samples were quenched at each examined temperature and analyzed in the SEM, were performed to confirm the reason for changes in the amount of Al2Cu at each stage. The results show that neutron diffraction effectively measured Al2Cu precipitation at temperatures between 200 and 440 °C. At temperatures between 460 and 520 °C, the reduction in Al2Cu peak intensity was due to dissolution of precipitates and interdendritic Al2Cu, while above 530 °C, it was primarily due to incipient melting. This research suggests that neutron diffraction is an effective technique in the in-situ analysis of solid-state and solid-to-liquid state phase transformations during heating.