Abstract: Experimental verification method and numerical simulation of ABAQUS in different medias were used to explore the mechanism of three quenching medias (water, 10%NaCl solution and engine oil) on the mechanical properties and residual stress of 7075 aluminum alloy. The numerical simulation results show that the residual stress after quenching in three medias shows the typical stress distribution characteristics of "internal tension and external compression". Moreover, the residual stress of the specimen after quenching with 10%NaCl solution is the highest, and that with engine oil is the lowest, which is related to the heat exchange state of the aluminum alloy surface in different medias. The tested results show that the salt crystals precipitated in the brine quenching process can make the vapor film on the surface of the specimen broken and have a better heat exchange rate, while layer of oil film formed in the engine oil quenching process reduces the heat exchange rate between the specimen and oil, leading to differences in mechanical properties of the alloys quenched in different medias. According to the hardness values of the quenched specimen from large to small, the three quenching medias are 10%NaCl solution, water and engine oil, which is consistent with the order of residual stress in the simulation results.

Key words: 7075 aluminum alloy, quenching, residual stress, numerical simulation