Microstructure and Mechanical Properties of Ti-6Al-4V by Electron Beam Rapid Manufacturing

Abstract:

Electron beam rapid manufacturing (EBRM) is a novel layer-additive manufacturing process which was developed to directly fabricate metal parts from computer aided design (CAD) data. The present study was conducted to evaluate the microstructure and the mechanical properties of Ti-6Al-4V by EBRM. Results show that typical microstructures exhibit large columnar β grains nucleated at the substrate and grew epitaxially along the height direction of deposits through many deposition layers, and alternately light and dark banded textures at layer-layer and bead-bead interfaces have been also found due to complex thermal history during deposition process. As a result, the tensile properties of the as-deposited and the as-annealed deposits exhibit distinct anisotropy. The strength in X and Y directions are similar and markedly higher than that in Z. No significant impact of annealing treatment has been found on room temperature tensile properties. Hot isostatic pressing (HIP) treatment obviously decreases the dispersion of the high cycle fatigue data and improves both ductility and toughness, while at the expense of the tensile strength. The tensile properties of the as-deposited and as-annealed Ti-6Al-4V by EBRM can meet the mechanical property requirements of AMS4999 standard, but can not fully meet the requirements of HB5432 standard.

Key words:electron beam rapid manufacturing; Ti-6Al-4V; microstructure; mechanical property