Serrated flow behavior in a near alpha titanium alloy IMI 834

Serrated behavior of near alpha titanium alloy IMI 834 has been studied at elevated temperature from 400 degrees C to 475 degrees C. Serrations morphology was found as A type of locking serrations followed by B type serrations at 400 degrees C. E type of serrations has been observed at higher strains at 425 degrees C. B type and unlocking serrations of CA type at 450 degrees C and again A and CB type serrations were found at 475 degrees C. In strength parameters, anomalous tensile behavior was found in the variation of tensile strength and yield strength with test temperature in the temperature range between 400 degrees C and 475 degrees C. However, the variation of normalized flow stress showed regions I-III with test temperature. Regions I and III correspond to normal tensile behavior and region II corresponds to anomalous tensile behavior. Blue brittle temperature of IMI 834 was attributed at 450 degrees C by confirming minimum ductility of 8.2%. In present study, a different approach has been adopted to show the change in deformation behavior during serrated region called as abrupt change in strain path. Maximum irregularity in flow behavior has been observed at 450 degrees C and 475 degrees C. Room temperature fractographic features showed transgranular features whereas mixed ductile and cleavage fracture has been observed in the temperature range between 400 degrees C and 475 degrees C. However, reverse slope behavior has been observed in the plot of critical strain versus test temperature at 450 degrees C, which could be due to silicide precipitation. In the present study, interaction of dislocations with interstitial/substitutional solutes is responsible for dynamic strain aging in IMI 834. (C) 2007 Elsevier B.V. All rights reserved.