Research On The Fabrication Process And Characteristics Of Al-Mg Aluminium Alloy By Wire And Double-Pulsed Arc Additive Manufacturing

The double-pulsed arc and wire additive manufacturing,used as the heat source,fabricate high density and mechanical properties metal components rapidly.Besides,it can greatly improve the material utilization rate,shorten production cycle,reduce production costs and increase production efficiency.The subject was based on the double-pulsed arc and wire additive manufacturing technology,taking the aluminum alloy component appearance,critical dimension,porosity,microstructure and mechanical properties as the research object,carrying out research of additive manufacturing process and technology.First,the multi-layer single channel specimens were studied,and the research was divided into two parts,which were the influence of low frequencies and arc characteristics on the structure and properties of the multi-layer single channel respectively.The first part:Under the condition that the other process parameters remained unchanged and only the low frequency changed,noticing that the double pulse arc had a better effect on gas elimination than the DC pulse arc.In addition,the deposited wall had low porosity and only the bottom of the it has the noticeable gas hole.The microstructure of multilayer single channel was composed of equiaxed grains.The deposition wall primarily consisted of a-Al and eutectic phase Al0.56Mg0.44 which formed a series of network structure.With increasing of low frequency,the average grain size firstly decreased and then increased,meanwhile,the micro hardness and ultimate tensile strengths were both firstly increased and then decreased.it reached the maximum at the frequency of 3Hz.However,the elongation rates appeared decreased firstly and then increased,at the same time,it reached the minimum at 3Hz.The ultimate tensile strengths in horizontal direction are always approximately 8.4MPa higher than that in vertical direction.Similarly,the elongation rates of these deposited walls in horizontal direction are also always 5%higher than that in vertical direction.The second part:Under the condition that the other process parameters remained unchanged and only the arc characteristic(characterizing hardness of arc)changed.With arc characteristic increasing,Waveforms of current and voltage transformed from rectangular to trapezoid and then to triangle,meanwhile,di/dt decreased in exponential-type.The roughness of side surface of multi-layer single channel straight wall was reduced,yet ripple profile showing in the vertical view became more and more unnoticeable.Both of graphs of grain size and heat input under various arc characteristics looked like W shape,which was contrary to graphs of the mean micro hardness and ultimate tensile strength showing the M shape.Importantly,the elongation rates of these deposited walls in vertical direction rise continuously.To conduct further study concerning the multi-channel weld spacing which was one of the key factors affecting the forming of deposited wall,steps were performed as follows:set up a simple model for optimal weld spacing algorithm,modify the algorithm based on experimental test and compare the porosity of various specimens which had different distance of weld spacing.It was illustrated that gas holes were mainly located at the welding spacing,the junction between layers and the bottom of central position in the bead.Furthermore,when the weld spacing was the optimal distance,porosity was relatively least.Eventually,the research on depositing 3D component was performed based on the double-pulsed wire and arc additive manufacturing system by establishing the 3D geometry model,planning complex paths,optimizing trajectory,writing online robot program,using relatively optimal parameters to automatically depositing component,finally detecting molding size.It was found that slope angel of oblique thin wall was only 1.7%between theoretical value and the actual.The coefficient of variance of thickness of outer wall was 2.288%,the same value of rib wall was 1.898%,which indicated that the wall thickness was uniform.Consequently,the DP-WAAM system can be used to manufacturing complex samples with high precision.