Microstructure And Mechanical Properties Of Ti-Ni-Based Functionally Graded Materials Fabricated By Dual-Wire Arc Additive Manufacturing

Ti-Ni-based functionally graded material（FGM）is a new material,suitable for aeroengines,large condensers and gas turbines and other fields that require high and complex service environments.The traditional preparation methods of Ti-Ni-based FGM has shortcomings such as hard to control the composition,limited size,and insufficiently dense parts.Dual-wire arc additive manufacturing（D-WAAM）technology can directly prepare Ti-Ni-based FGM through in-situ alloying,and has the advantage of precise control of composition,preparation component with large scale,dense parts,high efficiency,low cost,etc.Therefore,in this study,the preparation of Ti-Ni-based FGM was carried out by using D-WAAM technology,and related research was carried out.The main research includes:1)The effect of the gradient layer number on the microstructure and properties of FGM.The deposition experiments from Ti6Al4V to Inconel 625 were carried out with gradient layers of 1-layer,2-layer,and 4-layer,respectively.The results show that the FGM with gradient layer of 1-layer generated a large amount of Ni Ti₂ in the middle and lower area of the component and caused fracture.The deposition height of FGM with gradient layers of 4-layer was too high,so that the temperature difference between the top and bottom of the entire component is too large,then fracture occurs.Therefore,2-layer is the optimal number of gradient layers.2)The evolution of the microstructure of TA1/Ti6Al4V-Inconel 625 FGM.TA1/Ti6Al4V and Inconel 625 were used for the deposition experiment of Ti-Ni-based FGM,and the evolution of microstructure along the deposition direction of TA1/Ti6Al4V-Inconel 625 FGM was explored.The phase evolution of TA1-Inconel625 FGM from bottom to top can be summarized as follows:α-Ti+β-Ti+Ni Ti₂→β-Ti+Ni Ti₂+Ni Ti→Ni Ti+Ni₃Ti+（Cr,Mo）→γ-Ni+Ni Ti+Ni₃Ti+Laves+（Cr,Mo）.The phase evolution of Ti6Al4V-Inconel 625 FGM from bottom to top can be summarized as follows:α-Ti+β-Ti→α-Ti+Ni Ti₂→Ni Ti₂→Ni Ti₂+Ni Ti→Ni Ti+Ni₃Ti+（Cr,Mo）+Laves→Ni₃Ti+（Cr,Mo）.3)Mechanical properties of TA1/Ti6Al4V-Inconel 625 FGM.The minimum of the microhardness of Ti6Al4V-Inconel 625 FGM of 370 HV_0.2 is 108.72%larger than that of TA1-Inconel 625 FGM,which is 177 HV_0.2,indicating that Ti6Al4V-Inconel 625FGM is more resistant to deformation or damage.The compressive strength and strain is also better than that of TA1-Inconel 625 FGM,which is due to the presence of a large amount of Ni Ti₂ in the fracture of TA1-Inconel 625.Comprehensive consideration,Ti6Al4V is more suitable for the preparation of titanium-nickel FGM.In a word,this study systematically studied the preparation of Ti-Ni-based FGM by D-WAAM,provide new methods and research ideas for the preparation of FGM,broaden the application of WAAM,which is great significance to the research and development of FGM.