The effect of different microstructure on environmental embrittlement in a chromium-containing TiA1 alloy has been analyzed. The alloys having fully lamellar, nearly lamellar and duplex structure exhibited no apparent difference in the fracture strength and the tensile elongation at two test environments, vacuum and air. The near gamma alloy shows more strength higher and ductility in the vacuum than in the air. Tensile ductility increased to 3.5% in the vacuum, compared with 0.3% in the air. It can be argued that the gamma phase itself has relatively high intrinsic ductility, although a relationship with the ductility of alpha-2 is not yet clarified. An important factor to determine the environmental effect is the morphology and the volume fraction of alpha-2 phase in the alloy.
TiAl alloys incorporated in (0,3,5,10) wt.% TiB 2 dispersoids were manufactured via mechanical alloyingspark plasma sintering (MA-SPS), and their cyclic oxidation characteristics were studied at 800, 900 and 1000 o C in air. The cyclic oxidation resistance of the prepared TiAl-TiB 2 composites effectively increased with increases in TiB 2 content. The oxide scale formed consisted of an outer TiO 2 layer, an intermediate Al 2 O 3 layer, and an inner (Al 2 O 3 +TiO 2 ) mixed layer. The scale adherence was relatively good, and much thinner oxide scales, when compared to TiB 2 -free TiAl alloys, were formed on the prepared composites. The incorporated TiB 2 dispersoids oxidized to TiO 2 and B 2 O 3 which evaporated during oxidation.
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