Materials Science and Engineering A 527 (2010) 2572–2578 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea Sub-surface and surface analysis of high speed machined Ti–6Al–4V alloy J.D. Puerta Velásquez a , A. Tidu a,∗ , B. Bolle a , P. Chevrier b , J.-J. Fundenberger c a Laboratoire d’Étude des Textures et Applications aux Matériaux (LETAM), CNRS FRE 3143, Ecole Nationale d’Ingénieurs de Metz (ENIM), F-57012 Metz Cedex 01, France b Laboratoire de Mécanique Biomécanique, Polymère Structures (LaBPS), EA 4632 Ecole Nationale d’Ingénieurs de Metz (ENIM), F-57012 Metz Cedex 01, France c Laboratoire d’Étude des Textures et Applications aux Matériaux (LETAM), CNRS FRE 3143, Université Paul Verlaine de Metz (UPVM), F-57012 Metz Cedex 01, France article info Article history: Received 6 May 2009 Received in revised form 9 December 2009 Accepted 9 December 2009 Keywords: High speed machining Surface integrity Orthogonal cutting Titanium alloy abstract To understand the effects of cutting the surface integrity is an important goal to control the quality of a work piece. The current paper summarizes an extensive experimental study of the surface integrity and the sub-surface microstructure during high speed machining in orthogonal cutting condition. This study includes measurements of residual stresses and crystallographic texture in addition to electron microscopy observations. Our observations and conclusions are primarily focused on the effect of cutting speed considering a set of constant machining parameters on the microstructure evolution of the sub- surface of the material. The results allow a better understanding of the cutting process in high speed machining of titanium alloy Ti–6Al–4V. © 2009 Elsevier B.V. All rights reserved. 1. Introduction High speed machining (HSM) is a metal removing process widely used in industry for manufacturing various machine parts. It is well appreciated due to its high removal rates, reduction in production dead-times, low cutting forces and high precision. Moreover, it can achieve an excellent surface finish [1]. Titanium alloys are attractive materials for industrial applica- tions because of their high mechanical properties and excellent corrosion resistance at elevated temperatures together with a com- paratively low density. Despite these features, the utilisation of titanium alloys is still limited due to their poor machinability due to their thermal and chemical properties at high temperatures [2]. Because of the low thermal conductivity of titanium, the heat generated during the cutting process leads to an increase in the temperature around the cutting tool edge. Furthermore, the high chemical reactivity of titanium, which increases with the tempera- ture, produces an early damage of the cutting tool. This affects the final quality of the obtained metal surface, increasing the produc- tion costs [2]. Machining of titanium alloys has been a field of major inter- est for industrial applications and scientific research. During the cutting process, the original work piece is dissociated into the machined metal surface and the removed chips. Previous researches on chips obtained by high speed machining have been ∗ Corresponding author. Tel.: +33 387315395; fax: +33 387315377. E-mail address: tidu@enim.fr (A. Tidu). focused on the mechanics of chip formation [3,4], the chip geometry and morphology [5–10] and their microstructure and metallurgy [10,11]. Their investigations are fundamental to a better under- standing of chip formation and cutting process. A good amount of researches have also been conducted to characterise the plas- tically deformed sub-surface layer of the machined material. The depth of this deformed layer mainly depends on the mechanical and physical properties of the material but also on the machining parameters. High speed machining of the titanium alloys is an interesting subject because of the uniqueness of this cutting process. It is gen- erally believed that the deformation energy used during the metal cutting is transformed into heat energy near the cutting edge of the tool [8,12]. More precisely, heat energy is generated by the severe plastic deformation and heat conducts away from the pri- mary shear zone [4,8,12]. This phenomenon produces an important rise in the temperature followed by a rapid cooling in the adiabatic shear bands of the chips. A recent paper has shown that, in the case of the Ti–6Al–4V alloy, no phase transformation occur in this narrow zone [13]. Depending on the cutting speed, a percentage of this heat is transferred by conduction to the uncut material ahead of the tool. This phenomenon affects the mechanical and physical properties of the metal surface and sub-surface [8] The potential use of the EBSD technique for the investigation of deformation zones in metal cutting has been explored and was extensively introduced for steels by M’Saoubi and Ryde [14]. They investigated the extent of plastic deformation zones in chip root specimen and machined surfaces of single and two-phase steels. 0921-5093/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2009.12.018