Characterizing Microstructure Evolution and Kinetics of a Spray Formed Ultrahigh Strength Aluminum Alloy during Isothermal Aging

To better understand microstructure evolution during thermal mechanical processes, electrical conductivity tests were introduced to evaluate microstructure change in a spray formed ultra-high strength aluminum alloy. The results showed that porosity significantly influenced electrical conductivity in as-deposited state, and dissolution of alloying elements was the main factor for the variation during heat treatments. Microstructure observations revealed that porosity closure led to the increase in electrical conductivity after hot extrusion. The depletion of these atoms from Al matrix through precipitation nucleation, growth and coarsen contributed to the increase in electrical conductivity during aging treatments. Each contribution of microstructure matched well with Matthiessen rule.