The heterogeneous precipitation behavior of Al-Zn-Mg-Cu alloy was studied by high-throughput experiment based on end-quenching technology

Based on the quenching experiments and in combination with electrical conductivity measurements and microstructural characterization, the non-uniform precipitation behavior of the 7055 alloy was investigated. The study revealed that as the quenching rate decreased from 20.8 degrees C/s to 2.25 degrees C/s, the electrical conductivity increased from 27.8 %IACS to 30 %IACS, and both the types and nucleation sites of quenching-induced precipitates increased. The favorable nucleation sites for the precipitation were identified in the following sequence: high-angle grain boundaries (HAGBs), low-angle grain boundaries (LAGBs), non-coherent Al3Zr particles, dislocations, and coherent Al3Zr particles. The sequence of non-uniform precipitate formation included eta, S, T, and Y phases. With the reduction in quenching rate, the eta phase successively precipitated on HAGBs, LAGBs, noncoherent Al3Zr particles, and coherent Al3Zr particles. At a quenching rate of 10.5 degrees C/s, not only was the S phase observed to precipitate at high-density dislocation subgrains (SGs), but also the T phase was observed to precipitate at the non-coherent Al3Zr particles and subgrain boundaries (SGBs). When the quenching rate was further reduced to 2.7 degrees C/s, the precipitation of the Y phase was observed at SGs dislocations, and simultaneously, the precipitation of the eta and T phases was observed on the coherent Al3Zr particles within the SGs.