Microstructure And Properties Of 7075 Aluminum Alloy Fabricated By Controlled Diffusion Solidification

7075 aluminum alloy(Al-Zn-Mg-Cu)is widely used in aerospace and automotive due to its high strength to weight ratio and good ductility.However,7075 aluminum alloy does not offer its best mechanical properties and its microstructural deficiencies such as the macro-segregation and the hot tearing tendency of ingot casting are obvious,and the working process of aluminum alloy is difficult owing to its bad plasticity in ambient temperature.CDS(Controlled Diffusion Solidification)is a novel method in casting.In this paper,Using this method can acquire a fine and uniform primary ?-Al phase with non-dendritic.As it has a better feeding efficiency,this method could reduce the hot tearing and depress the formation of shrinkage.In addition,the CDS process is simple and the cost of production is reduced,so it has a great research significance.The 7075 alloy was fabricated by CDS technology,and the effects of precursor alloying component and mixing methods on the size,morphology and distribution of the primary ?-Al phase in 7075 alloy.Further,the solidification microstructure was investigated and the different process parameters were tested at room temperature,respectively.The main experimental results are as follows:(1)The primary ?-Al phase has the most favorable shape when the mixing ratio is 1:1at 637?.The average size of the primary ?-Al is 91.70 ?m and the shape factor is 2.56.The analysis reveals if the mixing temperature is same,the refining effect is increased when the component of Al-Zn-Mg-Cu is decreasing.If the pouring proportion is a constant,the temperature is lower and the primary ?-Al is fine and rounding.(2)The CDS process was innovated to enable casting alloys with a non-dendritic morphology of the primary ?-Al phase in the resultant cast microstructure and thus alleviating the problem of shrinkage porosity and obtaining a low-cost product with improved mechanical properties.(3)The solute gradient in the grain interface of CDS is smaller than in CC.Zn?Mg and Cu atoms have a high concentration in the eutectic phase of CC and CDS,it can easily form segregation.In the eutectic phase,the content of Cu atoms is the highest,Zn is in medium,Mg is the least.(4)In CC,the eutectic of 7075 aluminum alloy mainly is lamellar.While in CDS,the eutectic phase has much rod-like eutectic.the lamellar eutectic microstructure possibly acts as crack initiation sites during tensile test,thus resulting in the relatively poor tensile properties.While the rod-like eutectic have a excellent capacity to resist the tensile force.Thus,the result leading to the tensile strength and elongation of CDS samples more excellent than CC ones.(5)Compared with the average particle size and shape factor of the primary ?-Al phase,all of the CDS samples are smaller than CC.The tensile strength become increase with the decrease of particle size and shape factor.(6)This experimentation of tensile test could finite with three stages.Further,according to the microstructure morphology of each stage cross-section,combined with the knowledge of dislocation and made an explanation for its movement under the normal stress.In summary,using the method of CC for producing 7075 aluminum alloy is a promising approach.