Effect of primary α phase fraction on tensile behavior of IMI 834 alloy

Abstract

In the present work, the tensile behavior of IMI 834 alloy with varying primary α (αp) fraction in the transformed β matrix was studied at room temperature. Variation in αp phase fraction was obtained by changing the solution treatment temperature of the material in the α+β region from 1288K to 1333K. All the solution treated samples were then aged at 973K for 2hrs and cooled in air. Final microstructures consisted of various αp fractions (0.045 to 22 %) along with incoherent silicide precipitate (Ti, Zr)6Si3 and coherent Ti3Al precipitates which resulted in bimodal and lamellar microstructures. The αp phase fraction for bimodal microstructure was ranging from 3 to 22 % and that for lamellar microstructure 0 to 1 %. Tensile test results show that tensile strength increased with increase in αp up to ~ 15 % and further increase in αp from ~15 % to 22 % lead to decrease in tensile strength. The tensile test result also shows improvement in strain hardening with increase in αp. The higher tensile strength for samples with αp fraction up to ~ 15 % and lower tensile strength for sample with αp fraction ~15% - 22 % is attributed to effective slip length and solute partitioning effect, respectively.