Influence of Prior Deformation on the Development of Duplex Microstructures and Fatigue Strengths in Ti-6242

摘要

Unidirectional rolling with and without prior 3-dimensional (3D) pressing was carried out on the near-α titanium alloy Ti-6242. Duplex microstructures (α_p embedded in a lamellar (α+β) matrix) produced by simple unidirectional rolling followed by subtransus annealing exhibited microstructural inhomogeneities in the form of fairly large regions of similarly oriented constituents. Severe 3D-pressing prior to unidirectional rolling was found to homogenize the microstructure by eliminating these micro-textured regions. Comparing 3D-pressed plus rolled with simply rolled material, the fatigue strengths at R = 0.1 were much higher in the severely predeformed material. Slip band investigations indicated more homogeneous slip distribution and resulting higher resistances to fatigue crack nucleation as compared to the simply rolled material.