Local and Global Mechanical Behavior and Microstructure of Ti6Al4V Parts Built Using Electron Beam Melting Technology

Abstract

Laser and electron beam melting are prime technologies in metallic powder bed additive manufacturing in which parts are built layer by layer using high energy source. The technology is at a level where each layer can be as thin as 50 µm. Melting and solidification of each powder layer is typically accompanied by some subsurface melting to assure adherence and fusion of layers. In addition to anisotropic mechanical behavior of material caused by layering phenomenon, it is expected that the local mechanical behavior and microstructure vary throughout each build. In this manuscript, local and global mechanical behavior of Ti6Al4V parts produced using electron beam melting technology is investigated using bulk scale mechanical testing and nanoindentation. Parts fabricated in different build orientation were tested at different strain rates at a large scale. The experiment showed that strength is minimal perpendicular to the build plate. Additionally, material exhibited different local mechanical properties relative to distance from base plate. Investigation of the microstructure indicated very distinguished variations in the grain size and alpha and beta phase formation of material in different locations of part relative to build plate. Strength reduction in perpendicular direction is examined and explained through understanding of the microstructure and plastic deformation mechanism in α phase and prior β grains.