Effect of Sn, In, and Sb microalloying additions on the nucleation behavior of L12 Al3Zr precipitates

As the electrification of the automotive industry continues, dilute Al-Zr alloys have received increased interest due to the balanced strengthening and electrical conductivity provided by L1₂-Al₃Zr nanoprecipitates. Unfortunately, Al-Zr alloys require aggressive heat treatments due to the slow diffusion of Zr in Al. We recently found micro-alloying additions of Sn accelerate the isochronal age-hardening response of dilute Al-Zr alloys due to the favorable binding energy of Zr-Sn-vacancy triplets that lead to the nucleation of L1₂-Al₃Zr on Sn precipitates at 200°C. Based on characterization and first-principles calculations, we proposed a general Low melting point Element-Assisted Nucleation (LEAN) mechanism to explain the observed modified precipitation observed in the Al-Zr-Sn system during isochronal aging. Based on the first-principles binding energy calculations in our previous work, it is predicted micro alloy additions of In and Sb may produce a similar accelerated L1₂-Al₃Zr precipitation to the LEAN mechanism developed for Sn. To further validate the LEAN mechanism, this work examines the effects of In and Sb micro-alloy additions on the precipitation, age-hardening, and electrical conductivity behavior of a dilute Al-Zr alloy. The age-hardening and electrical conductivity behavior of the Al-Zr-Sn alloy are evaluated in simplified two-step heat treatments relative to isochronal aging.