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Robustness versus Performance Assessment for Different Gamma-TiAl Processing Routes Marc Thomas1 1 ONERA-DMSM, 29 avenue de la Division Leclerc, BP72, 92322 Châtillon, France ABSTRACT One of the main driving force for the development of advanced structural materials is weight saving especially in the transportation industry in order to reduce CO2 emission. The utilization of gamma aluminides, as good candidates for aerospace applications, is strongly related to the development of a cost-effective and robust processing route, as far as possible. It is well established that the processing route, i.e. cast, wrought or PM, has a dramatic effect on the microstructure and texture of gamma-TiAl alloys. Therefore, significant microstructural variations through post-heat treatments coupled with compositional modifications can only guarantee a proper balance of desired properties. However, a number of metallurgical factors during the processing steps can contribute to some scattering in properties. This review will highlight several critical process variables in terms of the resulting -TiAl microstructures. Of primary importance is the as-cast texture which is difficult to control and may contribute to prefer some alternative processing routes to ensure a better repeatability in mechanical results. Some innovative processing techniques for controlling the structure will then be presented. The main point which will be discussed in this paper is whether an approach leading to a robust process would not be at the expense of the high performance of the structural material. INTRODUCTION During the last years, aero-engine applications for -TiAl alloys have been seriously considered with the attractive potential for weight saving. Increased efforts were then devoted to optimize a commercially-viable route for the manufacture of aeroengine components [1], and gamma turbine blades are already introduced to General Electric’s GENx engine. In parallel, TiAl is currently being used for turbocharger rotors in automotive engine [2]. One key issue in processing is to ensure reproducible mechanical properties in order to guarantee minimum values that are acceptable for the end-users. However, the variety of alloys and processing routes reported in the literature result in a broad spectrum of microstructures and property variations for TiAl-based alloys. As a general rule, the processing routes used for a given TiAl-based alloy are known to differently affect the microstructure which in turn strongly governs the mechanical properties. Therefore, the ability to control the non-constant size, morphology, proportion and distribution of the constituent phases in -TiAl alloys and to optimize the microstructure over different length scales is a necessary requirement for a strict control of mechanical properties. Moreover, the variability of mechanical properties can be influenced by some processing factors that affect the microstructure, in particular crystal orientations, boundary misorientations, and structural inhomogeneities, thus leading to un