Fatigue crack growth behavior in a TiAl based aluminide with lamellar microstructure
Mine Yoji; Morofuji Yusuke; Ando Shinji; Takashima Kazuki; Tonda Hideki
Abstract:Fatigue crack growth behavior of a Ti-48Al-2Mn-2Nb (at%) alloy with lamellar microstructure has been investigated at room temperature in laboratory air. Single-edge-notched (SEN) specimens with different lamellar colony size and lamellar thickness were prepared by appropriate heat-treatments. The values of fatigue crack growth rate scattered largely for the specimens with large colony size. The highest crack growth resistance was obtained when the orientation of lamellar plates was aligned perpendicular to the crack growth direction. These results indicate that the lamellar orientation at crack tip dominates the fatigue crack growth behavior in the large colony sized specimens. For the specimens with small colony size, fatigue crack growth resistance appears to be averaged since the orientation of lamellar colony is random at the crack tip. Fatigue crack growth resistance in the air cooled specimens is higher than that in the furnace cooled ones. This may be due to the difference in lamellar thickness, type of lamellar boundary and/or quantity of a2 phase. Key Words:titanium aluminide, intermetallics, fatigue crack growth, lamellar microstructure, crack tip shielding