Microstructure evolution and strengthening mechanisms of electron beam welded 2219 aluminum alloy plate after hot spinning and heat treatment

Abstract

To investigate the feasibility of spinning the welded aluminum alloys, hot spinning tests were conducted on the electron beam welded (EBWed) 2219 aluminum alloy thick plates at 400 °C and successfully obtained a 2.8 mm curved welded-spun plate with a total thickness reduction of 72 %. The abnormal grain growth (AGG) phenomenon of the base material during hot spinning could be observed due to the reduced pinning effect of the θ-Al2Cu phases and static recrystallization, while the fusion zone exhibited homogeneous recrystallized microstructure. After hot spinning, the yield strength of the base material increased from 89.3 MPa to 133.6 MPa and the yield strength of the joint increased from 93.1 MPa to 134.7 MPa. To further optimize the microstructure and improve the mechanical properties of the spun alloy, the subsequent solid solution and aging treatment were conducted. Most of the coarse θ particles dissolved into the matrix and a large quantity of needle-like θ′ precipitates were generated. The yield strengths of the base material and the joint increased to 213.1 MPa and 216.4 MPa, respectively, which was mainly attributed to the precipitation strengthening of the θ′ precipitates. The comparison between the calculated yield stress and the experimental results showed that the contributions of different strengthening mechanisms in strengths were reliable.

Keywords

• Electron beam welding
• Abnormal grain growth
• 2219 aluminum alloy
• Strengthening mechanism