Creep Behavior of As-cast Ti-43Al-6Nb-1Mo-1Cr-0.2TiB2 Alloy at Elevated Temperature
The microstructure of as-cast Ti-43Al-6Nb-1Mo-1Cr-0.2TiB2 alloy was analyzed by XRD and SEM,and the creep tests were carried out at 760～840℃under 240～300 MPa.The deformed microstructure and fracture mor-phology were observed by SEM,EBSD and TEM to explore the effects of temperature and stress on creep deforma-tion and fracture behavior at elevated temperature.The results reveal that the as-cast alloy exhibits nearly lamellar structure,and the borides are dispersed in the matrix.According to the creep data,the stress exponent n and apparent activation energy Qc of the alloy in the test range are 6.64 and 388.37 kJ/mol,respectively.Meanwhile,it can be inferred that the creep deformation rate of the alloy is mainly controlled by dislocation climb combined with TEM obser-vation.Deformed microstructure and fracture morphology demonstrate that the creep fracture mode of the alloy is dominated by ductile-brittle mixed fracture.With the increase of temperature,the local ductile fracture area is expanded.With the increase of stress,the quantities of crack are increased.EBSD and TEM analysis indicate that great stress concentration occurs at the interface between B2 phase and γ phase at the grain boundary,leading to crack initiation.In addition,borides can hinder dislocation movement and promote dynamic recrystallization during creep.
High Nb-containing TiAl AlloyMicrostructureCreepDeformation BehaviorBoride
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