Effect Of Heat Treatment On Microstructures And Mechanical Property Of Inconel718 Alloy By 3D Print

Compared with forging which is a traditional forming technology of Inconel 718 alloy,3D printing has some advantages,such as short production cycle,low production cost,easy preparation of complex parts,etc.For this reason,Inconel718 alloy and TiC nano-particles reinforced Inconel718 alloy were preparated by SLM(a class of 3D printing technology)in this work.In order to research the microstructure evolution and the precipitation patterns of ? phase,?" phase,?? phase of Inconel718 alloy and TiC nano-particles reinforced Inconel718 alloy under different heat treatment process,the alloy were subjected to solution treatment,solution + aging treatment.Besides that,the relationship between the addition of precipitated phase,TiC nanoparticles and the mechanical behavior(tensile strength,Vickers hardness and elongation)of the alloy was studied,and the influence mechanism.The main conclusions are as follows:The SLM processing elliptical structure of Inconel718 alloy is composed of columnar crystals,with different sizes,with obvious direction,and the columnar grains in the microstructure of TiC nano-particles reinforced Inconel718 alloy are smaller in size.After 940?~1100? solution treatment,the columnar grains in the alloy is converted into equiaxed fine grains,there will be two morphological features ? phase precipitation in the alloy: short rod and needle,? phase has the chemical formula Ni3 Nb.When the solution temperature is 940 ? ~980 ?,the short-rod ? phase can be precipitated in the grain boundary,and the needle-like ? phase is precipitated in the crystal.The fracture surface of the alloy has dimples with uneven size,a small number of pores and crack source.When the solution temperature exceeds 1000 ?,the intra-crystal needle-like ? phase disappears,there is only the short rod ? phase at the grain boundary,and the number of short rod ? phase is obviously reduced,the fracture dimples increase and bigger than the alloy treated by lower solution temperature.The short rod ? phase can hinder the dislocation movement of the alloy during the tensile plastic deformation process,which is one of the main factors of the tensile strength and Vickers hardness of the alloy after 940?~980? solution were significantly higher than deposited alloy.When the solution temperature is1020?~1100?,the grain coarsening compare to the alloy after 940?~980? solution,and the elongation of the alloy is improved due to the dissolution of the harmful phase Laves phase and the dendritic segregation is improved.After 620-720? aging treatment aging treatment,a large number of dispersed acicular ? phases,disc-like ? " phases and the fine black dotted ??phases are precipitated in the crystal.Due to the covalence of the ?",?' phases and the matrix ? phase,a significant cohesive strengthening effect can be produced,which is one of the main reasons for the significant increase in tensile strength after aging.After adding TiC particles,the columnar grains are smaller in the sedimentary state of Inconel718 alloy.During the heat treatment,the precipitated phase in the alloy has similarity with the alloy without adding TiC.TiC particles has a good combination with the matrix of Inconel718 alloy,due to the strengthening of TiC particles,the tensile strength of the TiC nano-particles reinforced Inconel718 alloy is obviously improved compared to the alloy without adding TiC.