The Solidification Simulation And Properties Study Of Al-Zn-Mg-Cu Alloy With Zr And La Elements

Due to their high specific strength, good toughness, better corrosion resistance and other advantages, Al-Zn-Mg-Cu(7000) series aluminum alloys have been widely used in aerospace field and other transportation sectors. With the light weight of the aerospace equipments, Al-Zn-Mg-Cu alloys should have higher strength, toughness and stress corrosion resistance. However, the existing aluminum alloy treatment processes do not keep the high strength-high toughness-high resistance to stress corrosion good compatible. The comprehensive properties of Al-Zn-Mg-Cu series aluminum alloys can be improved by improving the casting process, optimizing the chemical compositions and designing the heat treatment process. The micro alloying can significantly improve the performance of the aluminum alloys. However, there are few reports on the Al-Zn-Mg-Cu-x Zr-x La. In this paper, we used ProCAST simulation software to simulate the casting solidification process of Al-Zn-Mg-Cu-0.1Zr-0.2La aluminum alloy, optimized the process parameters, combined with experiment and related performance test. Thus, we obtained the good aluminum alloy castings. The main conclusions of this paper are as follows:(1) The addition of trace Zr and La elements could be reacted with the aluminum alloy, fined the cast grains, improved the mechanical properties. The research showed that: 0.1Zr and 0.2La elements were the optimal amount of Al-Zn-Mg-Cu alloy.(2) The physical parameters, thermo mechanical coupling model and other related parameters of Al-Zn-Mg-Cu-0.1Zr-0.2La aluminum alloy were established by using ProCAST simulation software. Finally, we simulated the filling and solidification process of the aluminum alloy. We analyzed the distribution regularity of the temperature field and the stress field in different conditions, optimized the best casting process. The casting process parameters are as follows: the casting temperature is 740℃; the mold temperature is 210℃; the casting speed is 780mm/s. The flow field, shrinkage, microstructure, strength and crack of the best casting were simulated and analyzed. The simulation results were consistent with the experimental results.(3) According to the optimized casting process parameters of ProCAST simulation software, Al-Zn-Mg-Cu and Al-Zn-Mg-Cu-0.1Zr-0.2La aluminum alloys castings were cast. We studied the tensile properties and fracture morphology. Tensile strength test results indicated the tensile strength of the aluminum alloys with the addition of 0.1Zr and 0.2La elements after the solution aging treatment were significantly increased. Through analyzing the tensile fracture morphology, we found that adding 0.1Zr and 0.2La, the fracture mode of the alloys changed from the intergranular fracture to the dimple transgranular fracture, so the toughness of the alloys were improved.