Microstructure evolution and properties comparation of industrial grade-maintained 7050-T7451 plate recycled from machining chips

Abstract

There are 45%–71% machining chips generated during the manufacturing process of aviation components. Most of these MCs are down-grade recycled as cast alloy, causing resource waste. In this work, aviation MCs were added into the melt for grade-maintaining recycling. A systematic evaluation was conducted on the melt quality, microstructure evolution, and properties of industrial recycled 7050-T7451 plates with a capacity of 60t/furnace, as well as a comparison with the primary plates. The composition of the recycled 7050 melt is qualified, and the hydrogen content is below 0.075 mL/100gAl. The results of PoDFA and LiMCA show that the inclusions in the recycled 7050 melt are mainly below 40 μm in diameter, and the number of inclusions is 3 times that of the primary melt. TEM shows that the dispersed phase particles of the recycled plate are more uniform and finer. EBSD shows that the recrystallization ratio of recycled 7050-T7451 plate is 8.3%, much lower than the 23.9% of the primary plate. The mechanical and corrosion properties of the recycled 7050-T7451 all meet the AMS 4050 standard. The cost of grade-maintaining recycling can be saved by 6,130,000 USD per year for a production line with an annual output of 20,000 tons of plates. This work clarified the process, cost, microstructure, and properties of recycled 7050-T7451 plate, laying a foundation for the application of grade-maintaining recycled aviation aluminum alloys.

Keywords

• Machining chips
• Grade-maintaining recycling
• Recycled 7050-T7451
• Microstructure evolution
• Properties comparison