Research On Laser Welding Of Silicon Carbide Particles Reinforced Aluminum Matrix Composite

Silicon carbide particle reinforced aluminum matrix composite material（Si C_p/Al）has a wide range of engineering application prospects in aerospace,shipbuilding,automobile,electronics and other fields,and is a comprehensive and excellent metal matrix composite material.It not only has high hardness and low thermal expansion coefficient of Si C particles,but also has high specific strength and good plastic workability of aluminum alloy matrix,good thermal conductivity and good wear resistance.Although Si C_p/Al materials are considered to have great promise in composite materials,they are still not widely used.This is because the physical and chemical properties between the aluminum matrix of the material and the silicon carbide reinforced phase are quite different,and various welding defects are easily generated in the weld during welding,resulting in low weldability of the material.Common welding methods have various problems when welding this composite material,and the resulting joints are of poor quality.Therefore,on the basis of the past research,this paper carried out the research test of Si C_p/Al composite material weldability.Through the process test,parameter influence analysis,microstructure analysis,and mechanical property analysis,the welding process technical parameters that can realize reliable Si C_p/Al composites are found.In the research of this paper,it is found that the weldability of laser self-fusion welding is not good for Si C_p/Al composites,and there are two major problems of porosity and interface reaction.Therefore,a two-step solution was proposed.The first was to innovatively heat-extrude the original as-cast Si C_p/Al composite material;The second is to weld by adding an intermediate layer,innovatively using an inert intermediate layer that does not react with the base metal.In this paper,aluminum alloy and inert interlayer Ti B₂/Al are selected for welding experiments.After adding the interlayer,the weld formation is better,and the interface reaction is suppressed to varying degrees.It can be seen that when aluminum alloy is used as the intermediate layer,the hardness of the joint does not decrease significantly.Due to the fine grain strengthening in the center,the hardness is higher than that of the aluminum alloy itself.The tensile strength of the joint reaches 228MPa,which is much higher than that without the addition of the intermediate layer,which is increased by 80%.The joint hardness with the addition of 20%Ti B₂/2024Al intermediate layer is lower,which is caused by the existence of a large number of pores in the weld.Although the coexistence of Si C particles and Ti B₂ particles can improve the hardness,it still cannot offset the effect of pores.Due to the existence of pores,it is still difficult to greatly improve the joint strength.The tensile strength of the joint is 36MPa,which is only half of the welding without adding the intermediate layer.After adding Ti B₂,the fracture shows the form of brittle and ductile mixed fracture.The decrease in the tensile strength of the joint is largely due to the generated pores.Based on the theory of fluid dynamics and thermodynamics,this paper establishes a laser welding molten pool flow field analysis model,analyzes the distribution and migration process of the particle reinforcement phase during the composite welding process,and studies the influence of different intermediate layers on the molten pool flow.The finite element numerical simulation process is coupled with the results of welding experiments,weld morphology,weld particle distribution,and hardness testing.It is found that in the Ti B₂/Al intermediate layer welding model,the interface reaction of the weld is effectively suppressed,which is feasible Si C_p/Al welding method.