Influence Factors On Microstructure And Mechanical Properties Of TC4 Titanium Alloy By Electron Beam Wire Deposition

Electron Beam Wire Deposition(EBWD)is a near net forming additive manufacturing technology that uses an electron beam as a heat source and melts the external wire material to form a desired part and finally forms the desired part.It can realize moldless,high efficiency and low waste processing of complex titanium alloy structural parts.However,generally the macroscopic structure of EBWD titanium alloy is coarse columnar,and inhomogeneous microstructure in the columnar,which will have an adverse effect on the mechanical properties of the deposited layer,making it obvious anisotropy.How to improve the columnar grains in the deposited layer,homogeneous microstructure and reduce the anisotropy is an urgent problem to be solved in the EBWD titanium alloy.Therefore,in this paper,the TC4 titanium alloy as the research object,The macro and microstructure evolution,the method of controlling the homogeneous microstructure and the anisotropy of mechanical properties were studied by EBWD deposited titanium alloy.The main results are as follows:Heat input and wire feed speed have a direct impact on the macroscopic morphology of the deposited layer.When the heat input is too small,the wire cannot be melted smoothly.If the heat input is too large,the spatter is too serious to form.In the range of suitable heat input parameters,the height of the deposition layer decreases after the electron beam is increased,and the width of the deposit increases.After increasing the welding speed,the height of the deposition layer did not change significantly but the width decreased.After the wire feeding speed was increased,the height of the deposition layer increased but the width did not change significantly.Small heat input and high wire feed speed can deposit a fine layers.Reducing the heat input can shift the columnar grains in the deposition height direction.Increasing the wire feeding speed can cause the columnar grains transfor to equiaxed grains.When a small heat input and high wire feeding speed is used in TC4 titanium alloy EBWD,the coarse epitaxial growth of columnar grains in the deposition layer was improved,but there was a significant difference microstructure in the deposition height.The tensile strength of the deposited layer in the Z direction is comparable to the tensile strength in the middle-lower X direction but less than the tensile strength in the upper X direction.Solution temperature,solution time,cooling rate,aging temperature,and agingtime all have a direct effect on the homogeneity of the EBWD deposition samples.Increasing the temperature and time of solution and aging within a certain range can improve the homogeneity of the microstructure.However,if the temperature is too high or the time is too long,the microstructure will be coarsened,thereby reducing the homogeneity of the microstructure and mechanical properties;960°C,2h/AC+550 °C,4h/AC solution and aging heat treatment can make the EBWD deposition samples microstructure homogeneity.After EBWD deposition samples were treated by solution and aging heat treatment,the inhomogeneous structure along the deposition height direction was improved,homogeneous ? phase structure was obtained in the deposited layer,and the mechanical properties of the deposited layer were optimized to meet the requirements of the AMS4999 A standard,while further reducing The anisotropy of the deposited layer.