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A Ti-47Al-2Cr-2Nb (at.%) material was fabricated using two laser-based methods, “Selective Laser Melting” (SLM) and “Direct Metal Deposition” (DMD), for potential uses in aircraft jet engines. Experiments were conducted under controlled atmosphere by changing the processing parameters. Optimal parameters were searched for this relatively low ductility material to prevent cracking due to built-up residual stresses during fast cooling. It was observed that these non-equilibrium cooling conditions were fast enough to generate ultra fine and metastable structures exhibiting high microhardness values. Post heat-treatments were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve the residual stresses. A comparison of these two methods is provided in terms of powder requirements and of process parameters to achieve noncracked structures and fully dense materials.

Increased demands are reported from the commercial and military sectors for longer range, greater endurance, and improved durability aircraft, thus requiring more efficient turbine engines with reduced fuel consumption. The durability of components in aircraft engines, such as blades, depends on their ability to withstand the extreme thermomechanical stresses to which they are subjected under operational conditions. Meanwhile, the International Civil Aviation Organization (ICAO) is expected to implement further regulation in order to protect the environment from noise and greenhouse gas emissions, thus pushing engine developers to develop improved emission control systems. Therefore, there is still a strong need to develop cleaner and more efficient engines, which require technological advances in the thermal and mechanical properties of highperformance materials. With this increased demand of new generation engines requiring higher thrust/mass ratios, gamma titanium aluminide (g-TiAl) intermetallic alloys have a combination of properties which offer many benefits for low pressure turbine blades of aircraft engines. In this Communication, we show that the production of turbine blades in gTiAl alloys through spark plasma sintering (SPS) is a viable manufacturing route, by demonstrating that near-net shaping of g-TiAl blades is successful, and by developing an alloy with balanced and outstanding mechanical properties at room and high temperatures in a single run and without subsequent thermal treatments.It is recalled that intermetallic compounds are defined by a combination of two or more metal elements with simple atomic concentrations (50/50, 75/25, etc.) which results in an ordered crystallographic structure. In the aeronautic sector where qualities of strength and lightness prevail, TiAl was the first intermetallic compound to be investigated for substitution to conventional Ti-based alloys and Ni-based superalloys. Replacing nickel-based superalloys (density %8 g cm À3 ) by such intermetallic g-TiAl alloys (density %4 g cm À3 ) with high specific modulus and mechanical strength, combined with an exceptional resistance to oxidation, is an effective contribution to the development of lighter aircraft engines with high performance.Strong interest traces back to the late seventies with the difficulties to increase the operating temperature of Ti-based alloys due to serious problems of oxidation above 600°C. Since the early 1980s, Wright-Patterson Air Force Laboratories envisaged g-TiAl for applications in military turbine engines, but were confronted to its low deformability. The National Research Institute for Metals (NRIM) in Japan devoted extensive work based on alloying addition for ductilizing TiAl compound with some success. [1] Meanwhile, general electric developed in 1989 the reference Ti-48Al-2Cr-2Nb (at%) alloy [48-2-2], which is still widely studied today for turbine blade application. [2] Chromium and niobium elements were added to improve the tensile ductility and resistance to oxidation, respectivel...

a b s t r a c tSpark Plasma Sintering (SPS) is used to process TNB alloys. Pre-alloyed powders (Tie46Ale9Nb) were sintered between 975 C and 1300 C under 100 MPa. The microstructures of the products are determined by X-ray diffraction and by scanning and transmission electron microscopy. Their mechanical properties are evaluated by tensile tests performed at room temperature and creep experiments at 700 C under 300 MPa stress.Depending on the sintering temperature, two-phased, duplex and lamellar microstructures have been obtained. A quasi-a 2 phase has been observed, which is in fact an a 2 phase in which Nb atoms have substituted Ti atoms. The TNB alloys consolidated by SPS are stronger than the alloys previously elaborated by SPS using Tie47Ale2Cre2Nb and Tie44Ale2Cre2Nbe1B powders but they exhibit a lower ductility. Moreover, some specimens broke prematurely due to Fe inclusions.

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