Effect of Hot Deformation on Microstructure and Porosity of Additively Manufactured 7050 Al Alloy

Abstract

Wire arc additive manufacturing technology of 7050 aluminum alloy has a broad application prospect in aerospace field. But the lack of comprehensive properties caused by coarse columnar grains and pores becomes an important bottleneck. In this study, hot compression is conducted to simulate forging process to investigate the microstructure improvement of as‐deposited 7050 Al alloy by plastic deformation. The effect of temperature at 390–540 °C and deformation at 20%–60% on the microstructure and porosity is revealed. In the results, only slip deformation occurs at 420 °C and below. Local dynamic recrystallization occurs at columnar grain boundaries at 450 °C. Complete dynamic recrystallization occurs at 480 °C with the average grain size of about 60 μm. The microstructure overburns at 510 °C and above. The η eutectic phases are broken during deformation. The hot deformation accelerates the dissolution of η eutectic phases and the dissolution temperature of nano‐phases is 30 °C lower than solid solution. As the deformation amount increases from 20% to 60%, the deformation gradually extends from interlayer to inner of columnar grain layers. The spherical pores are first compressed to ellipsoid and then further compressed until completely closed. The pores are basically annihilated completely at 60% deformation with porosity of less than 0.1%.