Preparation And Properties Research Of High Strength And Toughness Al-Cu-Mg-Zn Alloy For Liquid Forging

In order to improve the defects that current aluminum alloy of liquid forging forming technology is easy to produce hot cracking, this paper mainly started from the aspect of optimizing the components of the aluminum alloy to design and produce new type of aluminum alloy with high strength and toughness that used in Liquid die forging technology. The new alloy’s hot cracking tendency should be as low as possible and its best mechanical properties can be reached the requirements: (?)≥450MPa、(?)≥7% and HB>115N/mm~2. Therefore, the new alloy can be used in place of conventional aluminum with higher hot cracking tendency and promote the development of liquid die forging technology further.The paper added a certain content of Zn, Mg and Cu elements on the basis of Al-Cu alloy to make the total elements beyond the traditional Al-Cu alloy and become a new type of Al-Cu-Mg-Zn alloy. The author changed Zn, Mg and Cu content of three primary elements by using a single variable method and designed twelve kinds of new type of alloy with different composition.2024 aluminum alloy was used as the substrate so as to prepare the new type alloy cylinder parts after alloy melting and unified process parameters of liquid forging technology.The relative size of the hot cracking tendency of the new alloy was tested by the constrained rod method, and compared it with the 7075 and 2024 aluminum alloy. The results showed that the HCS of 7075 and 2024 aluminum alloy is 68 and 64 respectively, and there were ten kinds of new alloys’HCS less than 64. Among the influence of the three main elements on the hot cracking tendency of alloys, the content of Cu element had the greatest influence on the HCS. When the content of Cu is about 5%, the hot cracking tendency of the alloy is the lowest and is 40.Using the tensile test, hardness test, TEM, SEM, XRD, OM and other testing and also micro structure analysis methods to compare alloy mechanical properties and microstructure observation. At last, the author selected the optimal performance of 8~#(Al-5Cu-4.5Mg-2.5Zn) alloy, and the mechanical properties of the original liquid forging parts is:σ_b=327MPa、δ=2.7%、HB=107N/mm2 and HCS=40. Similarly, the content of Cu had the greatest impact on the mechanical properties of the alloy.In order to further develop the mechanical properties of the new alloy, the paper explored the best technological parameters of ordinary heat treatment of 8~#(Al-5Cu-4.5Mg-2.5Zn) alloy by experiments. The result showed that when the homogenization treatment was at 470℃ for 24 hours, solution treatment was at 495℃ for 4.5 hours and artificial aging was at 200℃ for 18 hours, the microstructure of the workpiece is composed of G.P, S(Al2CuMg) phase and the PFZ and the optimal mechanical properties were obtained under this heat treatment process parameters. This subject achieved the purpose of the initial research, because of the optimal mechanical properties is:σ_b=469MPa、δ=7.6% and HB=208 N/mm~2.