激光增材制造Ti6Al4V-Inconel718功能梯度材料的成分变化和微观结构演变

Ti6Al4V/Inconel718 functionally graded materials were fabricated by laser additive manufacturing technology. The composition, phase composition, microstructure and microhardness of the gradient materials were studied. The results show that a series of phase transitions occur along the composition gradient direction: α+β→β+Ti₂Ni+TiCr₂+Ti-Fe→β+TiNi+TiCr₂+Ti-Fe→γ+Laves. The transition layer is mainly composed of binary phases including TiNi, Ti₂Ni, Ti-Cr, Ti-Fe, etc; the microstructure from the bottom to the top of the material changes from the Widmanstätten α-laths structure to the equiaxed β structure, and then it is epitaxially grown from equiaxed β structure into fine dendritic structure. The results of microhardness test show that the increase of hardness is mainly related to the decrease of α phase volume fraction, the increase of β phase, Ti-Ni, Ti-Cr and Ti-Fe phase, solid solution hardening and grain refinement. The maximum value in this study is 8230 MPa.