Study On Preparation And Application Of Al-Cu-Y Alloy Wire For Arc Additive Manufacturing

Alloy 2219（aluminum alloy welding wire grade 2319）has excellent mechanical properties,mechanical processing properties and welding properties,and is widely used in the aerospace field.With the rapid development of aerospace vehicles and weaponry,the requirements for light weight,high strength,large size and structural and functional integration of aluminum al-loy structural parts are getting higher and higher,and the requirements for room temperature and high temperature service performance of aluminum alloy materials are getting higher and higher,and the traditional materials and manufacturing and forming methods cannot meet the above development needs.The emergence of electric arc additive manufacturing technology can effectively solve the above development needs,and has significant advantages in the prep-aration of large and complex structures.Different from the traditional aluminum alloy welding wire,the WAAM technology puts forward higher requirements for the aluminum alloy wire.The uniform and stable control of the wire composition are very important,which is one of the key factors affecting the quality of the WAAM product.In the preparation process of special wire for WAAM,the selection of raw materials with stable process,low cost,uniform and controllable composition,and small fluctu-ation of composition range plays a crucial role in improving the quality and stability of WAAM products.Adding rare earth element Y to Al-Cu alloy can significantly increase and improve the strength and high temperature properties of the alloy.The preparation of Al-Re alloys by elec-trolysis has the advantages of low cost,in-situ synthesis of alloys,and the uniform and control-lable composition of electrolysis products.Therefore,starting from practical engineering appli-cation,this paper intends to develop the dissolution mechanism of rare earth oxide Y₂O₃ in Al F₃-（Li,Na）F fluoride salts system and the migration law of ion Y（III）and research on the physicochemical properties of Re O-Al F₃-（Li,Na）F fluoride salts system,and then electrolytic preparation of Al-Y master alloy.And the master alloy was used as raw material to prepare2319 aluminum alloy wires with different Y contents.The influence of Y contents on the micro-structure and properties of WAAM 2319 aluminum alloy at room temperature and high temper-ature was investigated,and the composition of rare earth Y modified 2319 alloy wires suitable for WAAM process was obtained.The above scope is to achieve application for specific prod-ucts.The main findings obtained are as follows:Based on the measurement of the migration number of Y（III）ions in the Al F₃-（Li,Na）F system by the Hittorf method in a three-chamber tank and the mechanism of migration and the COMSOL system to establish a model of the flow field-electric field coupling in both directions,the internal electric field distribution was simulated to verify the results showed that:in the Al F₃-（Li,Na）F-Y₂O₃ molten salt system in the temperature range of 900℃to 1000℃,the mi-gration number of Y（III）ions increases in the range of 0.70 to 0.80 with the increase of temper-ature,and the relationship is approximately linear;in the molar ratio of（Li,Na）F/Al F₃ in the range of 2.0 to 2.5,the migration number of Y（III）ions is relatively stable with an average val-ue of about 0.75;when the molar ratio of（Li,Na）F/Al F₃ is higher than 2.5,the migration num-ber of Y（III）ions decreases,from 0.75 to about 0.45 linearly;in the current density range of 1.0A/cm² to 2.0 A/cm² range,the mobility number of Y（III）ions increases with the increase of temperature in the range of 0.65 to 0.85,which is approximately linear.The density,conductivity,viscosity,surface tension chang with temperature and composi-tion of Al F₃-（Li,Na）F-（Al₂O₃-Y₂O₃）molten salt system with the（Li,Na）F/Al F₃（molar ratio）=2.5 in the temperature range from 900℃to 1000℃were measured by the Archimedes method,the continuously changing conductance cell constant method,the rotating method and the pull-ing cylinder method,respectively.The results show that the contents of Al₂O₃and Y₂O₃in the Al F₃-（Li,Na）F-（Al₂O₃-Y₂O₃）system is constant in the temperature range from 900℃to1000℃,and the density-temperature,viscosity-temperature and electrical conductivi-ty-temperature are all linearly related.At 950℃,the density of molten salt system decreases linearly with the increase of Al₂O₃ content,and increases linearly with the increase of Y₂O₃content.The conductivity decreases linearly with the increase of Y₂O₃or Al₂O₃ content.The viscosity increases linearly with the increase of Y₂O₃or Al₂O₃ content.By examining the effects of temperature and current density on the composition of electrolysis products,the optimal process conditions for electrolytic preparation of Al-Y alloys were obtained:temperature935℃,current density 0.7 A/cm²,the master Al-Y containing 5 wt%of Y was prepared.Using the Al-5 wt%Y alloy prepared by electrolysis as raw material,2319 alloy wires with different Y contents were prepared,and the effect of Y content on the microstructure and prop-erties of WAAM 2319 alloys was investigated.The result shows that Y can significantly refine the grains of WAAM 2319 alloy.With the increase of Y content,the grain refinement effects increase first and then decrease.When the Y content is 0.15 wt%,the grain refinement effect is the most significant.With the increase of Y content,the strength of WAAM 2319 alloy shows a trend of first increase and then decrease,and the elongation gradually decreases.When the Y content is 0.15 wt%,the WAAM 2319 aluminum alloy shows the best performance,the tensile strength is 484 MPa,the yield strength is 348 MPa and the elongation is 10%.The effect of Y content on the microstructure and properties of WAAM 2319 alloy held at200℃for 30 mins was investigated.The results show that the Y content has no significant ef-fect on the number and size of pores in WAAM 2319 alloy at high temperatures.The addition of Y can significantly refine the grain size of WAAM 2319 alloy under high temperature condi-tions;the grain size is reduced from 43.15μm to 26.15μm,and the grain size is uniform.With the increase of Y content,the grain size of the WAAM accumulation at high temperature de-creased first and then increased,the number and size of the undissolvedθphase continued to increase,and the number of the equilibriumθphase formed by transformation first increases and then decreases.The addition of Y can improve the high-temperature mechanical properties of the WAAM 2319 alloy.With the increase of Y content,the high-temperature mechanical properties of the WAAM 2319 alloy show a trend of first increasing and then decreasing.The accumulation with Y content of 0.15 wt%has the largest number of equilibriumθphases formed by transformation,and the alloy has the best high-temperature mechanical properties,the tensile strength is 319 MPa,the yield strength is 296 MPa,and the elongation is 10%.According to the optimized Y content range,Y-added 2319 alloy wire was prepared,and a certain type of engine nozzle which was implemented in the engineering application was pre-pared by the WAAM process.