Interface Reaction Behavior And Microstructure Control Of Laser Melting Deposation Welding Of SiCp/2024Al

SiCp/2024Al composite materials have many excellent properties,such as high specific strength,low density,high wear resistance,good thermal conductivity,and low coefficient of thermal expansion.It is mostly used in parts that require light weight but high wear,such as automobile pistons and fighter landing gear.For its thermal performance,it can be used in places where the heat is extremely uneven on the aerospace.At present,there is not much research on the connection of SiCp/2024Al composite materials,mainly diffusion welding and friction stir welding.Aiming at various problems caused by it,such as: burning loss of reinforced phase,uneven distribution of reinforced phase,low welding efficiency,pores,and cracks,the principle of laser fusion deposition was proposed to connect them.First of all,this subject uses a mixed powder of 20% SiC and 2024Al powder to conduct a flat plate laser melting deposition additive manufacturing test.The main research is on the influence of process parameters(laser power,scanning speed,powder feed amount)on the forming quality.It was found that this method can be used to deposit the powder on the surface of the flat plate,but there are some problems that the layers are not fused and the interface reaction is violent.By adjusting the amount of heat input,a deposition area with less interfacial reaction and good interlayer fusion can be obtained.On this basis,the V-groove flat butt welding of the composite material was developed,and the plate used was 2 mm thick.During the welding process,the back side is not fully penetrated.By changing the groove angle and gap,the wettability of the melt on the back side can be improved.Porosity and cracks extending to the base material were generated in the deposition area.By controlling the combination of process parameters,the generation of porosity and cracks was effectively controlled,and a well-formed joint was obtained.Tested for its performance,the tensile properties reached about 147 MPa.Secondly,this article conducted a thermodynamic analysis of the interface reaction of the joint and found that the main guiding factor of the interface reaction is temperature.Under the premise of controlling the temperature,the occurrence of the interface reaction can be effectively controlled.However,controlling the temperature will bring about problems such as macro forming and poor connection between the deposition zone and the base metal,so the possibility of controlling the interface reaction by adding other elements is analyzed next.The addition of Si element can prevent the generation of intermetallic compounds by inhibiting the reaction,and the addition of Ti element can replace Al element to preferentially react with SiC to generate TiC without significant effect on the joint strength.On this basis,the temperature field simulation was carried out under different heat input of the joint.At 0.01 m/s,the tendency of the interface reaction of the laser power less than 1000 W was low.Finally,for the problem of poor fusion at the interface,an energy spectrum analysis was performed on the unfused region,and it was found that SiC particles were aggregated between different deposition layers.In order to quantitatively study the mechanism of SiC being expelled,a model of SiC particle motion near the interface was established,and it was found that the main forces acting on the SiC particles were gravity,viscous resistance,and interface force.Taking the 10?m particle size as an example,the movement speed variation rule near the interface is calculated.If it is not captured before it reaches the interface,it will eventually remain relatively still with the interface in the liquid phase and eventually be discharged from the deposition area.Then,the critical velocity curve of SiC particles with different particle diameters was analyzed,and finally the SiC particles with a particle diameter of 40-60 ?m were more easily captured by the interface.