Cube texture due to dynamic recrystallization in Pb and PbSn alloys under Equal Chanel Angular Extrusion processing

R. E. BOLMARO; V SORDI,; M FERRANTE,; WEIMIN GAN,; G BROKMEIER, H

Pittsburgh

Congreso; 15th International Conference on Textures of Materials; 2007

ECAE has been one of the most prolific techniques in the study of severe deformations of metallic alloys. Severe deformation on low melting temperature alloys has been scarcely studied due to the high dynamic recrystallization effects they usually present. In the current presentation we show ECAE deformation experiments performed in a 120o tool at room temperature in pure Pb and eutectic Pb-62%Sn alloy. The samples were passed 5 times in a route A. Metallographic observation after each pass showed a completely recrystallized structure. Due to the high absorption presented by Pb for X-rays the textures were measured by neutron diffraction. Because of their high penetration and superior statistical capabilities the textures showed well defined patterns even in the cases when the strength was rather weak. The textures presented a well defined Cube component rotated approximately -26 degrees around an axis coincident with the transversal direction. Even on the two-phase Pb-62%Sn samples the cube component was clearly the major and better defined one. Despite Pb is a Low Stacking Fault Energy (LSFE) FCC metal, the pure Pb sample and the Pb-rich phase in Pb-62%Sn sample show a recrystallization texture resembling the regular static recrystallization texture presented by High Stacking Fault Energy (HSFE) FCC materials after rolling and heat treatment. The nature of the recrystallization process is discussed taking into account the texture results. Because of the severe deformation it is possible that the subgrain size, due to fragmentation, might have reached a value close to the thickness of the original grains after they have been deformed. Geometric Dynamic Recystallization (GDR) is the most probable mechanism but that hypothesis is difficult to test because of the readily occurring recrystallization.