Enhanced strength-ductility synergy of β-solidifying TiAl alloy with preferred lamellar orientation by texturing high-temperature α phase through hot extrusion

A preferentially-aligned lamellar structure in TNM alloy with enhanced strength-ductility synergy is successfully obtained by texturing the high-temperature alpha phase through hot extrusion. The lamellar orientations of the resultant lamellar colonies inherit the texture feature of the extruded high-temperature alpha phase ({0001} basal fiber texture), exhibiting a preferential distribution with 60% of the lamellar traces {0001}alpha/{111}gamma nearly parallel to the extrusion direction (ED). The influence of the microstructural variables on the deformation mechanisms and fracture mechanisms are elucidated by microstructural characterization and crystallographic analysis. Results show that when the lamellar trace is parallel to the tensile direction (TD//ED), twinning and stacking faults in the gamma laths are favorable to be activated. The origin of the enhanced strength-ductility synergy is attributed to the combined effects of twinning, stacking faults and its induced dislocation slip, as well as the extra interaction stresses introduced by the multiple deformation mechanisms and the alpha 2/gamma interfaces. This study can provide a novel strategy for microstructural regulation and design of high-performance beta-solidifying TiAl alloys.