| The arc additive manufacturing technology has become one of the most competitive forming technologies in the fields of high quality,full density,forming economy and rapid manufacturing of metal parts due to the advantages of short manufacturing processes and cycles,low raw material waste,high manufacturing efficiency,and low manufacturing cost.However,the technology still needs to be explored to improve forming accuracy,part organization and performance uniformity.In order to enhance the structure and performance of aluminum alloy parts manufactured by arc additive manufacturing,this article studies the CMT arc-micro forging composite additive manufacturing deformed aluminum alloy,including the 5A56 arc free deposition process,the arc-micro forging process for non-heat treatable 5A56 aluminum alloy as well as microstructure and properties of heat treatment 2319aluminum alloy before and after heat treatment effect.The main conclusions are as follows:(1)Based on the response surface method,the response surface regression equation of5A56 aluminum alloy arc free deposition process parameters to arc voltage,welding current,heat input and aspect ratio was established.Based on the multi-objective optimization of the regression equation,the single-pass weld head and the difference in morphology and the problem of liquid metal flow in a single straight wall,the head acceleration and interlayer temperature control strategies were formulated,and the final optimized process parameters were obtained.The results of verification experiments show that the single-pass straight-walled parts obtained by the optimized process have satisfactory macro-morphology and small machining allowance.(2)The morphology and microstructure of 5A56 parts were studied.The results show that the deformation of the arc-micro forging process decreases with the height of the straight-walled parts due to the interlayer remelting.The arc-micro forging process does not change the distribution of inter-layer and inter-layer junction and top,but it reduces the number of columnar dendrites between layers,making the structure of each part finer and more uniform,and transform the?phase(Mg5Al8)from a continuous skeletal distribution to discontinuous spherical distribution,that strengthens the intercrystalline bonding.The arc-micro forging process plays a role in refining and homogenizing the grains and strengthening phase,and the work hardening effect of micro rolling.According to the results,the tensile strength?b,yield strength?0.2 and the elongation?reached 349MPa,205MPa and 20.4%.(3)Comparative analysis of the structure and performance of the 2319 parts before and after heat treatment.The results show that the rolling fracture and heat dissipation of the micro-forged rolls change the Z-structure of the non-heat-treated parts from the as-cast structure and the equiaxed grains to complete equiaxed grains,and greatly improved the distribution of the second phase and grain morphology within the cell boundaries.After heat treatment,the grains grow and the micro-forged parts are released due to the deformation energy,so that the recrystallization is more completely during the heat treatment process.The phase is influenced by the state of the structure before heat treatment,and is more denser and finer than the distribution of the arc-deposition state in the crystal.In terms of mechanical properties,the effect of the micro-forging process after heat treatment on strength has been greatly reduced compared with that before the heat treatment,indicating that the 2319 aluminum alloy mainly focuses on precipitation strengthening after heat treatment,but the micro-forging process has refined the grains and the second phase before heat treatment.The homogenization effect,the suppression of the?"phase precipitation and the GP area by the amount of deformation are still conducive to improving the plasticity and reducing the anisotropy of the performance.The tensile strengths?b of the micro-forged alloy in the X and Z directions are 464MPa and453MPa respectively,the yield strength?0.2 is 314 MPa and 302 MPa respectively,and the elongation?is 11.1%and 8.0%respectively,far exceeding the ASTM B247M-2015 standard die forging standard. |
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