Microstructure and tensile properties of hot fogred high Nb containing TiAl based alloy with initial near lamellar microstructure

High Nb containing TiAl based alloy with a nominal composition of Ti–44Al–8Nb–0.2W–0.2B–Y (in at%) exhibiting near lamellar microstructure was fabricated. Cylindrical blanks were quasi-isothermal forged at 1275°C for 0.05s−1, with a total reduction of 70%. The as-forged blanks were furnace-cooled (F...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2015-08, Vol.642, p.16-21
Main Authors: Zhang, S.Z., Zhang, C.J., Du, Z.X., Hou, Z.P., Lin, P., Chen, Y.Y.
Format: Article
Language:English
Subjects:
Blanks
EBSD
Intermetallic compounds
Intermetallics
Mechanical characterization
Microstructure
Orientation relationships
Phase boundaries
Recrystallization
Tensile properties
Thermomechanical processing
Titanium aluminides
Titanium base alloys
Titanium compounds
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Summary:High Nb containing TiAl based alloy with a nominal composition of Ti–44Al–8Nb–0.2W–0.2B–Y (in at%) exhibiting near lamellar microstructure was fabricated. Cylindrical blanks were quasi-isothermal forged at 1275°C for 0.05s−1, with a total reduction of 70%. The as-forged blanks were furnace-cooled (FCed) or air-cooled (ACed). The microstructure of the as-forged alloy mainly consists of remnant lamellar colonies (RL) and broken-down (BD) area caused by inhomogeneous deformation. Lamellar orientation and α2 lath thickness strongly affect the deformation of lamellar colonies. In the RL structure, the α2 phase s are remain in lath states and the γ laths recrystallized. The Blackburn relationship between the previous α2 lath and the γ lath in the RL structure is disrupted. Meanwhile, stress induced α→γ phase transformation generates the optimal perfect Blackburn relationship between the parent α2 lath and newborn γ grains. Cooling rate significantly affects the as-forged microstructure, thereby influencing the bulging rate of γ phase boundaries into α2 phases. Cooling rate also influences the tensile properties of the alloy.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2015.06.066