Acta Materialia 51 (2003) 1651–1662 www.actamat-journals.com Sintering of commercially pure titanium powder with a Nd:YAG laser source P. Fischer a,∗ , V. Romano a , H.P. Weber a , N.P. Karapatis b , E. Boillat b , R. Glardon b a Institute of Applied Physics, Laser Materials Processing, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland b Laboratory for Production Management and Processes, Mechanical Engineering Department, Swiss Federal Institute of Technology, Lausanne, Switzerland Received 20 June 2002; received in revised form 26 November 2002; accepted 28 November 2002 Abstract To understand the process of pulsed selective laser sintering, two different energy coupling mechanisms have to be considered. In a first step, the energy is absorbed in a narrow layer of individual powder grains determined by the bulk properties of the material. This leads to a high temperature of the surface of the grains during the interaction. After thermalization of the energy, heat flows mainly towards the center of the grains until a local steady state of the temperature within the powder grain is obtained. Afterwards, the surrounding powder properties have to be considered for the further thermal development. According to these model assumptions, a numerical simulation of the heat flow equation has been performed and compared with experimentally obtained titanium plates, which allowed to obtain a process map.  2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. Keywords: Pulsed Nd:YAG laser; Sintering; Metals; Numerical simulation 1. Introduction Among layered manufacturing (LM) techniques, selective laser sintering (SLS) [1–3] exhibits a high potential in the field of rapid tooling (RT) and rapid manufacturing (RM), due to its capability to directly build up three-dimensional (3D) metallic components. In SLS, invented in 1991 by Deckard ∗ Corresponding author. Tel.: +41-31-631-8940; fax: +41- 31-631-3765. E-mail address: fischer@iap.unibe.ch (P. Fischer). 1359-6454/03/$30.00  2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. doi:10.1016/S1359-6454(02)00567-0 at the University of Texas at Austin, USA [4], a localized region of a thin powder layer is consoli- dated by means of the energy of a focused laser beam, controlled according to a sliced 3D CAD model. Recent advances in metallic SLS have improved the technology (http://www.eos-gmbh.de), although it still remains limited in terms of material versatility, quality and precision; the method essentially relies on empirical, experimental knowledge and still lacks a strong theoretical basis. In this paper, a very brief theoretical background on laser radiation coupling into material is