Study On The Dynamic Microstructural Evolution Of The2026Aluminum Alloy During Hot Deformation

2026aluminum alloy is developed to enhance and improve the safety and durability ofexisting airplanes, it contains low levels of Fe and Si, and minor addition of Zr to inhibitrecrystallization during thermo-mechanical processing. In this paper, the compression tests of2026aluminum alloy were performed at elevated temperature on Gleeble-1500. Therelationships between flow stress and strain rate，deformation temperature and deformationdegree of2026aluminum alloy during compression at elevated temperature were studied.Microstructure evolution and dynamic precipitation behavior of2026aluminum alloy duringcompression at elevated temperature were analyzed by using optical microscopy（OM）,transmission electron microscopy（TEM）, scanning electron microscopy（SEM） and X-raydiffraction（XRD）. The relationship between the performance and the microstructure of thealloy was studied by hardness test.The result shows as follows:（1） The flow stress of2026aluminum during compression at elevated temperaturedepends strongly on the strain rate and deformation temperature. The results show that thetrue stress-true strain curves exhibit a peak stress at a critical strain, after which the flowstress decrease monotonically until the high strain, showing a dynamic flow softening, thepeak stress level decreases with increasing deformation temperature and decreasing strainrate.（2） With the temperature increasing and the strain rate decreasing, the grains trended togrow up. The disloation density increased first and then decreased, the dislocation andsubgrain displayed different configurations as the true strain increased. With increasingtemperature, the microstructure evolution process completed earlier.（3） The2026aluminum alloy showed a dynamic precipitation behavior during hotdeformation, the main three precipitates were the S（Al₂CuMg） phase, the θ（Al₂Cu） phase andthe Al₃Zr phase. During the early deform stage, the orientation and the distribution of S and θprecipitations were damaged, and then, the re-dissolution and re-precipitation of theprecipitation happened. The re-dissolution rate of S phases was faster while the re-dissolutionof θ phase and Al₃Zr particles seldom occurred. As strain increases, the three phases nucleatedin terms of homogeneous nucleation and heterogeneous nucleation. Some S phases and θphases nucleated on the Al₃Zr particles. There was a trend of increasing in number andcoarsening after deformation. The Al₃Zr precipitates grew faster when they were connectedwith S phases and θ phases, and they displayed an evolution from the LI12type to the DO23 type. With higher temperature, the dissolution rate was faster, the particles tended toprecipitate from saturated solid solution and with lower temperature and higher strain rate,particles prefered a heterogeneous nucleation and precipitation. Under high deformation rate,the dissolution rate was also faster and the heterogeneous nucleation increased but the growthand coarsening of precipitates reduced.（4） The hardness of2026aluminum alloy have close relationship with deformationtemperature, stain rate and true stain. The hardeness increased first and then decreased duringdeformation.With the deformation temperature and strain rate increasing, the HV hardnessincreased obviously. The hardness change of2026aluminumduring hot deformation was themultiple effects of strain hardning, solid solution strengthening, precipitation strengtheningand precipitation redissolved and coarsening.