Influence of Shake-Out Time on the Solidification Deformation and Mechanical Properties of A357 Stress Frame Casting

摘要

The Al-Si-Mg ternary eutectic alloy of A357 was applied to the aviation and aerospace field widely due to itsrnexcellent casting process performance, the thin-walled structures that manufactured by this alloy was prone to occurrndeformation by the solidification residual stress. The effect of shake-out time on the solidification deformation has notrnbeen given sufficient attention and research. In this study, a stress frame casting was designed and manufactured with therngravity pouring, the distribution of temperature difference field under different shake-out time (33.3 min, 66.6 min andrn133.3 min) was tested with using of K-type thermocouple, the microstructure and mechanical properties of the stressrnframe castings were investigated by means of OM, SEM, EDS analysis and tensile testing machine, the solidificationrnresidual stress and deformation analysis were completed by the X-ray residual stress analyzer and three-dimensionalrnlaser scanner. The results indicate that the cooling rate of the thin rod area is greater than the intersection region, the flatrnarea has the lowest value in the initial solidification process, then the intersection region is higher than the thin rod arearnafter 12.4 min. With the delay of shake-out time, the distribution of temperature difference field is decreasing, along withrnthe continuous reducing of cooling rate. Choosing the shake-out time at the medium solidification temperature stage (33.3rnmin), the overall cooling rates of stress frame casting are rising continuously due to the huge heat transfer between therncasting and the air, owing to the larger heat transfer surface area of flat region, the distribution of temperature differencernbetween the thin rod and flat areas are changing conversely, which offset the solidification deformation partially. A largerrnsolidification deformation is obtained when shake-out at the 66.6 min because of its increasing temperature difference, thernsolidification process is completed absolutely when choosing the shake-out time at 133.3 min. The maximum solidificationrnresidual stress and deformation are attained at the shake-out time of 66.6 min, solidification deformation of the flat andrnthin rod regions obey the four polynomial mathematical distribution, the shake-out time has a little effect on thernmicrostructure and mechanical properties of the stress frame casting.