Effect of Annealing Process on Microstructure and Properties of Rolled Semi-Solid billet

Abstract:

In this paper, deformation heat treatment of 7075 aluminium alloy semi-solid billet was carried out by asynchronous rolling process. The effect of recrystallization annealing on microstructure evolution and mechanical properties of the deformed semi-solid sheets was studied. The recrystallization degree and grain size change trend of the annealed sheet under various process parameters were analyzed, and the recrystallization mechanism of the deformed semi-solid sheet during annealing was summarized. The results show that the recrystallization order of microstructure is deformed eutectic phase, deformed primary solid phase, and deformed intragranular “droplet”. When the annealing process is held at 470 ℃ for 20 min, the recrystallized grain size of the annealed sheet is smaller and the comprehensive mechanical properties are better. The tensile strength and elongation of the annealed sheet are 408 MPa and 28% respectively. The increase of annealing temperature will lead to the transition from brittle fracture to ductile fracture, but too high annealing temperature will lead to hot cracking, which will greatly reduce the mechanical properties of the plate.