Research On Process And Mechanism Of TIG Additive Manufactured Aluminium Alloy With Nano-TiC Particles

As a lightweight and high-strength material,aluminum alloys are widely used in aerospace and automotive industries.Traditional methods such as cutting or casting can not meet the requirements for the rapid manufacturing.Wire and arc additive manufacture has a low manufacturing cost.The arc filler wire additive manufacturing has become one of the rapid forming methods of metal parts because of low manufacturing cost and high production efficiency.However,the problem of coarsening of the aluminum alloy in the arc additive has not been solved.The addition of nano-particles can refine the grain structure,which is expected to solve the problem.In this paper,4043 aluminum alloy wire was selected as welding wire.6061-T6 aluminum alloy plate with a thickness of 4 mm was selected as substrate.Nano-Ti C particles with a particle size of 50-200 nm were added during additive Manufacturing.Then single-pass single-layer and single-pass multi-layer additive experiments were performed.In this paper,the influence of process parameters on the macro morphology of welding specimens was first studied.For the single-pass single-layer welding samples,the effects of various process parameters on the weld width and height were obtained.And the forming law was further characterized by the appearance forming coefficient.For single-pass multi-layer welding samples,the effect of various process parameters on layer width and layer height was obtained.It was found that with increasing coating amount of nano-Ti C particles,the layer width decreases and the layer height increases.When the coating amount of Ti C particles is too large,macro morphology was deteriorated.Then the influence of different process parameters on the microstructure and mechanical properties of the welding samples was studied.According to the difference of microstructure,the samples were divided into three areas.The upper layer,the middle layer and the bottom layer.The microstructural characteristics of each area were analyzed in detail.It was found that increasing the coating amount of nano-Ti C particles,reducing the wire feeding speed,and reducing the welding current can refine grains.In addition,the proportion of different crystal grains in the same weld bead is changed.The proportion of fine equiaxed crystals is increased.The ratio of coarse cylenoids and columnar crystals is reduced.The strength and hardness of the samples are improved.When the coating amount of nano-Ti C particles is too large,the elongation rate of weld samples decreases.Finally,combined with the distribution of nano-Ti C particles and its influence on the microstructure evolution,the strengthening mechanism of nano-Ti C particles in the aluminum alloy arc additive manufacturing was analyzed.The nano-Ti C particles are stable during the additive manufacturing process.Most of the particles are distributed at the grain boundaries and some are in the interior of the grains.Grains at the grain boundary can obstruct the grain boundary movement,inhibit grain growth,finally refining the grain structure.Fine grain strengthening is the most important strengthening mechanism.