Analysis of the solidification characteristics of a 319 type Al alloy using in-situ neutron diffraction

Abstract

Aluminum alloy 319 have been used extensively in automotive powertrain applications in recent years to improve vehicle fuel efficiency. To further optimize the casting processes associated with this Al alloy, a better understanding of the solidification characteristics is required. In this study, in-situ neutron diffraction was used to examine the phase formation temperatures and growth characteristics of the primary Al dendrites, Al-Si eutectic and Al2Cu intermetallic phase. Differential scanning calorimetry and FactSage™ simulations were also carried out and related to the results from the in-situ neutron diffraction. The results indicate that the growth profiles as a function of temperature were similar to the Scheil model simulations in FactSage™ for each major phase in the alloy. This shows an initial growth of the primary Al phase followed by a large increase in Al solid fraction near the Al-Si eutectic temperature. The formation and growth of the Al-Si eutectic and Al2Cu were also similar to that predicted by the simulations, which showed a large increase in the solid fraction of these phases near the phase formation temperatures.