Research On CMT Additive Manufacturing And Strengthening Mechanism Of 5356 Aluminum Alloy With TiB₂ Particles Added

Aluminum-magnesium alloys are widely used in aerospace,automotive,and other fields due to their lightweight,high strength,excellent corrosion resistance,and other properties.However,the traditional aluminum-magnesium alloy forming technology is increasingly difficult to meet the needs of rapid prototyping of complex components and its performance development has also encountered bottlenecks.CMT arc additive forming technology has become one of the rapid metal forming methods due to its ability to quickly and accurately form complex-shaped components with low cost.However due to the large heat input and complex thermal cycle in the process of additive forming,made of aluminum alloy material after forming organization exists in the uneven porosity,organization,and the problems of coarse grains.It is proposed that adding reinforcing phase particles TiB₂ in the additive process can refine the grain size,homogenize the microstructure and inhibit dendrite segregation,which is expected to solve the shortcomings of the aluminum alloy CMT arc additive forming method.In this paper,the ER5356welding wire is selected,and TiB₂ particles are introduced into the process of CMT arc additive forming 5356 aluminum alloy to carry out the forming test of single-channel layer and multi-layer wall components.In this paper,the effects of TiB₂ particles on the forming and the stability of the CMT arc were firstly studied.The study shows that the addition of TiB₂ particles increases the monolayer melt width and the monolayer height.With the increase of particle content,the melt width decreases first and then increases,and the addition of TiB₂ particles affects the droplet transition of CMT.In the short circuit stage,particles float up,resulting in speckled pits on the surface of forming.When the added content is too high,the forming will be seriously affected.Then,the effects of TiB₂ particles on the microstructure and mechanical properties of the additive samples were studied.The results showed that the addition of TiB₂ particles could significantly refine the grain size,homogenize the microstructure,weaken the texture characteristics of the microstructure,and improve the distribution of the low angle grain boundaries and change the distribution and morphology of the second phase.At the same time,the addition of TiB₂ particles can improve the mechanical properties of the samples and basically eliminate the anisotropy of mechanical properties.The fracture analysis shows that the fracture mode of the additive sample is the ductile fracture and the fracture mechanism is microporous aggregation fracture.Finally,the influence of TiB₂ particles on the thermal cycle and solidification process of the additive was analyzed.The addition of TiB₂ particles can effectively improve the stability of the solidification process,and both the particles themselves and the grains generated by non-uniform nucleation on their surfaces can limit the growth of columnar and dendritic grains.At the same time,there is a good mismatch between TiB₂ particles and Al matrix,which causes the distortion of Al lattice and the increase of lattice constant,thus improving the diffusion ability of solute atoms,and making the second phase disperse and precipitate around the TiB₂ particles.Finally,the microstructure evolution and strengthening mechanism of CMT additive of 5356 aluminum alloy doped with TiB₂ particles were summarized and put forward.