Ductility Anisotropy Induced by Ferrite in Direct Laser Deposited 17-4 PH Steel: Combined Microstructure and Dislocation Density Simulation

摘要

The anisotropic ductility of a direct laser deposited 17-4 PH cubic part was investigated.Anisotropic elongations in the specimens from varied surfaces of the part were obtained:~6.2%,~1.5%,and~4.5%in XY,YZ,and XZ samples,respectively.Furthermore,various orientations of ferrite were found in different specimens,taking the loading direction as reference.A finite element analysis depending on actual microstructures and dislocation density revealed that the orientation of ferrite caused the ductility anisotropy.The orientation of ferrite affected its plastic deformability and the deformation compatibility between phases during the uniaxial loading.The ferrite parallel to the tensile direction in the YZ sample had the worst deformability and induced severe strain localization and stress triaxiality,which resulted in inferior ductility.The ferrite perpendicular to the tensile direction showed the best deformability,whereas strain localization remained intense in the XZ sample owing to the unmatched deformability of martensite.The inclined ferrite in the XY sample exhibited moderate deformability and was found to enhance the plastic flow of martensite,leading to the best deformation compatibility and ductility.