Microstructure and mechanical properties of Ti6Al4V/Inconel718 functionally graded materials by directed laser deposition

Ti6Al4V/Inconel 718 functionally graded material combines the advantages of the two materials, it can fully meet the requirements of high temperature resistance, high strength and light weight in the extremely harsh environment of aerospace. Ti6Al4V/ Inconel 718 functional gradient materials were prepared by directed laser deposition. Scanning electron microscopy and electron probe micro-analysis were used to observe the microstructure and element distribution of functional gradient samples. The mechanical properties of the functionally graded sample were measured by Vickers hardness tester. The results show that the interface between Ti6Al4V and Inconel 718 is cleavage fracture, and the cleavage fracture is related to the formation and concentration of Ti2Ni, NiTi and Ni3Ti intermetallic compounds. A well-formed gradient sample is prepared by using gradient transition. Through the effective gradient transition form(100%Ti6Al4V- 90%Ti6Al4V/10% Inconel 718-80% Ti6Al4V/20% Inconel 718-100% Inconel 718), the element inhomogeneity at the interface is alleviated and a good metallurgical bond is formed. Along the gradient direction, the microhardness gradually increases with the increase of Inconel 718, reaching the maximum of 811HV. The reason for the increase in hardness is related to solid solution and precipitation strengthening of Ti2Ni intermetallic compounds.