Abstract
A novel strategy of microstructure design is introduced to improve the mechanical properties of TiAl alloys, fabricated by powder metallurgy. The gas atomization powder and as-HIPed (Hot isostatic pressing) TiAl are investigated by scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy, and electron backscattered diffraction. The dispersed submicron precipitate in the microstructure is determined to be Y2O3. A microstructure with uniform fine grain is obtained. The room temperature strength and strain reach 793 MPa and 1.5%, respectively. The strength and strain at 700 °C are still as high as 664 MPa and 9.2%, respectively. The fine grain and precipitate lead to a high room-temperature plasticity.
Highlights
TiAl alloys are a new type of promising lightweight material [1,2,3]
The microstructural development and mechanical properties of the submicron precipitate-reinforced β-TiAl alloys produced by powder metallurgy (PM) are investigated
The powder of the TiAl alloys was produced by electrode induction melting gas atomization (EIGA)
Summary
TiAl alloys are a new type of promising lightweight material [1,2,3]. The TiAl alloys could be a good substitute for superalloys due to their low density, high specific strength, high Young’s modulus, and oxidation resistance at 700–900 ◦ C [4,5]. The TiAl produced by the traditional casting method and ingot metallurgy method have coarse grains and a non-uniform microstructure, which is disadvantageous for the high-temperature performance of TiAl alloys. TiAl alloys via powder metallurgy (PM) result in outstanding mechanical properties, owing to their uniform and fine microstructure [8]. TiAl powder needs to be degassed in a vacuum before HIP. Gerling degassed TiAl powder at 500 ◦ C/0.003 Pa [9]. Liu degassed TiAl powder at 500 ◦ C in a vacuum for 12 h [10]. Combining the Y addition and PM method might result in high-plasticity precipitate-reinforced TiAl alloys. The microstructural development and mechanical properties of the submicron precipitate-reinforced β-TiAl alloys produced by PM are investigated
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