| Aluminum bronze alloys have excellent strength,corrosion resistance,and wear resistance,making it widely used in the manufacture of propellers,turbines,flanges,and other marine equipment.The above components are traditionally manufactured by casting technology.However,defects such as pores in the castings will reduce the mechanical properties of the components.In addition,the production technology such as mold opening makes the manufacturing cost high and the production cycle long in the personalized and small-batch production process.Cold metal transfer wire arc additive manufacturing has advantages such as low heat input,short production cycle,low manufacturing cost,and good mechanical properties.It has important application prospects in the manufacturing of large and complex aluminum bronze alloy components.Therefore,based on the CMT-WAAM,this thesis conducted aluminum bronze alloy WAAM experiment on Q235low-carbon steel substrate,and studied the macro-forming,microstructure,and mechanical properties of single-layer single-pass deposited layer and single-pass multi-layer thin-wall.Firstly,the effects of wire feeding speed and other parameters on the macro-morphology,microstructure and mechanical properties of single-layer single-pass deposited layer were studied.The results show that with the increase of wire feeding speed,the width,depth,height coefficient,cross-sectional area and dilution ratio of cladding layer increase,and the height of cladding layer increases first and then decreases.Other process parameters,such as welding speed,CTWD and welding torch angle,all have certain influence on the macroscopic size.It is found that when the process parameters are not suitable,the surface of the cladding layer will appear uneven spreading and fold oxidation phenomenon,so it must be appropriate to match the process parameters.With the increase of wire feeding speed,the morphology of Fe-rich phase changed from needle shape and granular shape to snowflake shape and dendritic shape.Controlling other parameters unchanged,when the wire feeding speed is 7m/min,due to the large increase of Fe-rich phase,the microhardness of the cladding layer reaches the maximum of 165 HV.The bonding strength between cladding layer and matrix is higher,metallurgical bonding occurs,and the shear strength is greater than 640 MPa.Secondly,the test results of single-pass multi-layer thin-wall show that the average width of the sample is positively correlated with the wire feeding speed,while the average height of the sample is negatively.When the wire feeding speed increases,the roughness increases and the forming accuracy decreases.The maximum effective area reached 79.57%when the wire feeding speed was 5m/min.The microstructure is mainly composed of α-Cu phase,β’ phase and κ phase.The bottom area of the sample is mainly fine and dense equiaxed crystal,and the grain size changes abruptly with the increase of the number of deposited layers,showing a larger columnar crystal.The inner region of the sample is still dominated by columnar crystals,but the grain size increases somewhat.The size of α-Cu phase in the interlaminar region is larger than that in the inner structure,and more β’ phase remains in the laminar zone.The direction of tissue growth in the top region of the sample was disordered.The microhardness of the top region of the sample is significantly lower than that of the middle and bottom regions,and the hardness of the two sides of the wall is lower than that of the central region.The hardness increases gradually with the increase of wire feeding speed,wire feeding speed is 7m/min,up to 154 HV.The tensile strength is anisotropic.The tensile strength of transverse sample is 521 MPa higher than that of longitudinal sample 485 MPa,but the elongation of longitudinal sample is obviously higher than that of transverse sample.The effect of wire feeding speed on tensile strength is not obvious.The impact performance of the samples is good,and the impact energy is above47 J.Finally,it is found that after quenching treatment,α phase grows,β’ phase increases sharply,κ phase is basically solidly dissolved into α phase.After quenching and tempering treatment,the microstructure becomes relatively uniform,the size of α phase is larger than that of additive state,β’ phase decomposes,and κphase dissolves.After tempering treatment,α phase size is smaller than quenching+tempering state,a certain amount of κ phase precipitation,β’ phase in the form of massive distribution on the α phase grain boundary.The hardness of the hardened sample is 189 HV,which is 34.04% higher than that of the additive state,and the hardness of the hardened+tempered and tempered states is 14.89%lower than that of the additive state.The quenched specimens have the highest tensile strength(526MPa)but the lowest elongation after fracture(31%).The tensile strength of quenched+tempered and tempered specimens decreases to a certain extent,but the plasticity increases.The impact energy of the quenched+tempered sample is up to 98 J,which is increased by 71.93% compared with the additive state,and the impact energy of the tempered sample is increased by 56.14% compared with the additive state. |
