SAXS high-temperature analysis of heat treatment conditions in AA7050 to assess precipitate evolution and strengthening mechanisms

Metal microstructure analysis during high-temperature exposure relies on using furnaces and other machinery to heat and then quench samples to analyze residual material microstructure in order to gain insight on heat treatment efficacy. This traditional workflow is effective but can limit the ability to fully understand high temperature conditions in the material, particularly precipitation kinetics and other material dynamics. Characterization of materials in high temperature conditions becomes increasingly important so that these materials can be more closely observed and better understood in order to improve process and heat treat design. Current work at University of Kentucky focuses on the ability to analyze metal microstructure evolution during heat treatment by using small-angle x-ray scattering techniques in combination with a heated stage to simulate four different heat treatment conditions in AA7050 aluminum. In this study SAXS was used to measure precipitate size and volume fraction at regular intervals while heat treating samples at 160 – 220℃ for 0 – 120 minutes. Precipitates were measured with diameters ranging from 5 – 10 nm with samples heat treated at 220℃ showing largest precipitate growth, increasing in size from 5.5 – 9 nm during the 0 – 120 minute heat treatment time. Connections between precipitate growth, volume fraction, and material hardness are explored as microstructures evolve during these various heat treatment conditions.