富氧近α钛合金复合片层组织的微织构生成机制和力学行为OA

To address the strength-ductility trade-off dilemma of high-oxygen powder metallurgy(PM)titanium alloys,two types of near-α titanium alloys(880-PE1 and 880-PE2)with α/βt composite lamellar microstructure and oxygen mass fraction of 0.36%are fabricated via the combination of sintering and hot extrusion process.The crystal size and morphological characteristics are analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The crystallographic orientation features are examined through X-ray diffraction(XRD)macro-texture and electron backscatter diffraction(EBSD)micro-texture analysis.The relationships between microstructure and mechanical properties and deformation mechanisms are studied by combining room-temperature tensile tests and dislocation bright-field imaging observations.The results show that the 880-PE1 specimen exhibits no obvious micro-texture.Cracks initiate at grain boundaries of α phases during plastic deformation,resulting in a low elongation to fracture of only 8.9%.The 880-PE2 specimen develops a micro-texture with the<0001>direction of α grains aligned parallel to the extrusion direction.This unique micro-texture can effectively activate pyramidal<c+a>dislocations,which move via wavy slip and give rise to an extraordinary increase in work-hardening rate.Additionally,lamellar distortion and grain-boundary deformation compatibility are effectively promoted,and the initiation of intergranular cracks is suppressed simultaneously.Ultimate tensile strength of the 880-PE2 specimen reaches 1070 MPa,and the elongation to fracture increases to 22.0%,achieving synergistic improvement of strength-ductility.