Microstructural Study to Investigate Creep Properties of IMI685 Near Alpha Ti Alloy
Abstract
Jayanthi A, M. Anil Kumar and B. Ravisankar
IMI 685 is a near alpha (a) titanium alloy used in compressor discs for aero engines due to its high creep resistance. This work mainly focuses on detailed microstructural study of a real forging of size Æ400 x 75mm height both in as forged and heat-treated condition. The forging was carried out in a+b(beta) region and b region. Creep properties at 520°C, stress of 300MPa for 100h duration were evaluated for both conditions and compared. The b forged forging showed higher creep resistance (0.06% plastic strain) than a+b forged forging (0.14% plastic strain) due to the difference in grain size and grain boundary thickness which is reflected in steady state creep rate also. The steady state creep rate was nearly 3 times higher in a+b forged compared to b forged suggesting forging at b region gives higher creep resistance.