Study On The Process And Mechanical Properties Of ZL205A Aluminum Alloy Parts Prepared By Selective Laser Melting Technique

ZL205A alloy is a high strength and toughness cast aluminum alloy.With high specific strength and stiffness.Is in the aerospace field some key parts mainly used alloy materials.But its casting properties are poor.In addition,the shape and structure of aluminum alloy parts become more and more complicated and require high performance.The Aluminum Alloy traditional casting technology has been difficult to achieve.In this paper,ZL205 A alloy powder is taken as the object of study.The SLM forming parameters of ZL205 A alloy powders were mainly studied,microstructure and mechanical properties of its formed parts.The main research contents and conclusions are as follows:Studied that the influence of the technological parameters of selective laser melting forming on the densification of ZL205 A alloy powder SLM forming sample was studied,In the other process parameters within a certain range,the thickness of the powder layer has little influence on the density of the sample.The optimum processing parameters for SLM forming of ZL205 A alloy powder were obtained: The laser power 450 W,scanning speed of 1200mm/s~1400mm/s,scanning spacing0.09 mm,thickness of 40?m,the density can reach more than 98%.Paper has analyzed microstructure and mechanical properties of ZL205 A alloy powder SLM forming sample,Microstructure grain of ZL205 A alloy powder SLM forming sample is very small,the phase size of the alpha-Al matrix is about 1?m,and the solid solution phase is first crystallized,most of the Cu exists in the liquid phase.Because of rapid cooling,the Cu element precipitates blocked,and then the Al2 Cu phase is formed.The Al2 Cu phase distributes uniformly in the alpha-Al matrix and divides the alpha-Al matrix into small islands.The microstructure is divided into three regions: fine crystalline region,heat affected zone and coarse grain region.The microstructure of specimen is not completely uniform,fine grained region as the center area of the molten pool,for the fine grain structure;coarse grain zone is the molten pool or overlapping zone remelting zone,due to repeated remelting,become coarse grain structure.In the range of other technological parameters,with the increase of scanningspeed,the tensile strength and yield strength of SLM formed ZL205 A alloy firstly increased and then decreased.When the scanning speed is 1000mm/s,Ultimate tensile strength and yield strength are 281 MPa and 221 MPa,and the elongation is 4.2%.In the process of selective laser melting,the thermal influence between the inner parts of the sample leads to the formation of SLM.The average hardness of the ZL205 A alloy in the X-Y section is higher than that of the X-Z section.When the laser energy density is 140J/mm3 and 112J/mm3,the SLM forming ZL205 A alloy sample has many obvious small dimples at the fracture surface,and it is a typical ductile fracture,A small amount of spherical particles on the surface,and a small number of round holes,are caused by inert gas argon deposited in the molten pool during melting.When the laser energy density is 80J/mm3 and 62J/mm3,the dimple of the alloy sample is less,and more aluminum alloy powder particles can be seen clearly.The formation and mechanism of the main defects such as residual stress and warpage during SLM forming of ZL205 A alloy powder were investigated.It is found that the ZL205 A alloy powder forming SLM than other Aluminum Alloy powder(Al-Si alloy powder)is more difficult,mainly in the powder forming difficulty,easy ball and poor surface quality,large size spherical particles are significantly more obvious hot crack.The internal temperature gradient of SLM forming parts is the main cause of residual stress,decrease the pool surface temperature difference can reduce the residual stress,the risk of warpage and cracking of parts can be reduced by appropriately reducing the laser energy density and adding a reasonably dense support structure type.Through the study on technology and properties of ZL205 A alloy powder forming SLM,ZL205 A alloy samples were prepared,provides a theoretical basis for the industrial application of selective laser melting of ZL205 A alloy powder rapid prototyping.