**1. Introduction**

Additive manufacturing (AM) is the newest powder metallurgy (PM) technique [1-3] while Ti-6Al-4V is the single most important Ti alloy [4-9]. AM Ti-6Al-4V is being widely pursed by research community and industry for its capability to produce complicated, net-shape engineering parts and/or customised, biomedical implants.

This chapter begins with an introduction of the fundamental properties of Ti-6Al-4V, and its densification mechanism, typical microstructure and mechanical property achievable by conventional PM routes. This functions as a point of reference for the following discussion of the AM Ti-6Al-4V in terms of densification, microstructure, and mechanical property. The mostly popular laser-based AM techniques, namely selective laser melting (SLM), electron beam melting (EBM), laser metal deposition (LMD) and selective laser sintering (SLS), for the fabrication of Ti-6Al-4V have been overviewed based on an analysis of over 100 individual studies. Heat treatment is essential to most of the AM Ti-6Al-4V. Principles for selecting appropriate heat treatment for the AM Ti-6Al-4V are proposed based on martensite phase transformation and optimisation of mechanical properties. Oxygen impurity is an issue to most Ti materials and it is addressed in this chapter as well; counter measurements to mitigate oxygen have been suggested which involves the use of rare earth based materials.

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
