Microstructure and mechanical properties of Ti–6Al–4V alloy fabricated using electron beam freeform fabrication

Abstract

Electron beam freeform fabrication (EBF3) has drawn increasing attention over the past decade due to its potential for time and cost savings. The microstructure and mechanical properties of EBF3- fabricated Ti–6Al–4V block have been investigated and discussed in this work. The microstructure of the as-fabricated block was found to be dominated by columnar grains and equiaxed grains. The phase constitutions were identified by X-ray diffraction and transmission electron microscopy. The results reveal that the as-fabricated Ti–6Al–4V samples consist of lamellar structure, basketweave structure and Widmanstätten structure. The graded Ti–6Al–4V microstructure was observed which mainly arise from the complex thermal cycles. The average width of lamellar α phase and element content of Al are decreased with the increasing of the building height. Graded mechanical properties of Ti–6Al–4V with microhardness and tensile strength were found. The microhardness and ultimate tensile strength increase while decreasing elongation as the increasing of build height. This work provides a better understanding of microstructural evolution during the EBF3 process, which will be conducive process control, improvement, and optimization.