Research On AlSi10Mg Doped CNTs Laser Selective Melting And Its Process Performance

Due to its light weight,low thermal expansion rate and good mechanical properties,the Al Si10Mg sample with complex geometry manufactured by laser selective melting technology has a wide range of applications in aerospace,automotive and other fields.Although the strength and hardness of Al Si10Mg alloy by laser selective melting have been greatly improved,compared with titanium alloy and stainless steel,its strength and hardness are still relatively low,and its ductility is poor,which limits its wide application.In order to solve the disadvantages of Al Si10Mg alloy with low strength,low hardness and poor ductility,it has been widely used.The researchers added nanomaterials and particulate materials to Al Si10Mg to form aluminum matrix composites that are lightweight,low thermal expansion,good weldability,high strength,high hardness,and good ductility.At present,although some researches have been conducted on the laser-selective melting of aluminum-based composite materials,the laser-selective melting and forming of aluminum-based composite materials is still in the development stage.Carbon nanotubes(CNTs),as a new type of nano-reinforced materials,are rarely reported in China by using laser selective melting to form CNTs-Al Si10Mg composite materials.In this paper,first,AlSi10Mg powder is used as the research object,and the laser selective melting technique is used to discuss the effect of different scanning speeds on the sample forming,and the optimal experimental parameters are obtained.Then laser selective melting to obtain a well-formed sample of CNTs-Al Si10Mg composite material,using OM,XRD,SEM and other instruments to systematically analyze the microstructure and phase composition of the sample,combined with test data such as hardness and tensile,By analyzing the relationship between microstructure and performance,the following conclusions are obtained.Selective melting of the AlSi10Mg laser to obtain the influence of scanning speed on the melting width,penetration depth,depth-to-width ratio,pore type,porosity and surface roughness.After analysis,the optimal process parameters of laser power 160W and scanning speed 800mm/s were obtained.Scanning distance H=70?m,layer thickness L=20?m.Scanning electron microscope was used to compare the microstructure in the XY plane and XZ plane of the CNTs-Al Si10Mg sample.The grain size is different.The size and orientation of the grains at the bottom and middle and upper parts of the XZ plane are different.After analyzing the CNTs-Al Si10Mg sample by transmission electron microscopy,it was found that there were tubular carbon nanotubes with a length of 300-400 nm inside the sample,and the carbon nanotubes were distributed along the grain boundaries.Phase analysis showed that in the CNTs-AlSi10Mg sample,in addition to the?-Al phase and the precipitated eutectic Si,a nano-scale tubular structure with a length of 533 nm and a width of 63 nm was found at the grain boundary of the?-Al phase.It is considered to be a carbon nanotube whose outer wall is covered with Al₄C₃.The hardness of the CNTs-AlSi10Mg sample in the XY plane and the hardness in the XZ plane are different,but they are higher than the laser selection melting and casting Al Si10Mg.At the same time,the tensile properties of the CNTs-Al Si10Mg sample have also been greatly improved.The fracture morphology is a cleavage step,and there are a large number of small dimples at the step.Based on the analysis of the laser selective melting CNTs-Al Si10Mg strengthening mechanism,it is considered that there are three ways to strengthen the material after adding carbon nanotubes to Al Si10Mg:fine grain strengthening,second phase strengthening and load transfer strengthening.These three strengthening methods work together to improve the mechanical properties of aluminum matrix composites.