Fatigue Strength Plateau Induced by Primary Alpha Phase Size in TC11 Alloy

Enhancing the fatigue strength of materials by increasing their tensile strength is generally considered as an effective strategy. This study observed a fatigue strength plateau in TC11 alloy: despite significant variations in tensile strength, the fatigue strength of TC11 alloy demonstrates remarkable stability. It is determined that this anomalous behavior is governed by a unique fatigue cracking mechanism associated with the primary α phase (α p ) in dual‐phase titanium alloys due to the pilling‐up of dislocations and consequent cleavage (pillingup‐cleavage). Under this mechanism, the critical cracking stress is predominantly influenced by the pilling‐up distance of dislocations (reflected in the size of α p phase) and is relatively independent of the lattice frictional resistance (expressed in the nanoindentation hardness of α p phase). This leads to the occurrence of fatigue strength plateau in TC11 alloy in this study.