Rolling Equipment Performance Asynchronous Stack Of Ultrafine Copper And Twins

The ultra-fine-grained twin copper with special grain boundary structure performs high strength and excellent electrical conductivity properties, it has become an important research problems in materials field. The optical microscope, scanning electronic microscrope (SEM) and transmission electronic microscope (TEM) technique were used to experimentally investigate the ultra-fine-grained twin copper prepared by AARB (Asymmetrical Accumulative Rolling Bonding) and treated by recrystallization annealing. The grain refinement mechanism of AARB copper, mechanism of interface composite, the character of grain boundaries in annealing, the recrystallization and ultrafine twins mechanism of six passes AARB copper were studied. Meanwhile, the mechanical properties, microhardness, electrical conductivity and corrosion resistance of copper were researched. The conclusions are listed below:1. The mechanism of grain refinement was obtained in AARB process:with the shear strength and pressure stress, the original grains were crushed and stretched along rolling direction when AARB for one and two passes. After three passes of AARB deformed, the grains further refinement, part of grains were splited into small large angle grains and dislocation transfered form grain boundary to intercrystalline gradually. When AARB for four and five passes, grain refinement mainly based on accumulation strain, most of grains broken into small grains and subgrains. When AARB for six passes, cumulative strain effect became weaker and obtained relatively uniform copper grain, the average grain size was1.0p.m.2. The compound mechanism of the interface during AARB process:under the effect of shear stress and compressive stress, parts of original grains were flatten and breaken to piece in planting plane. After2passes, it appeared fiber structure and during the increased of deformed passes, the fiber structure became thin and some of them cut off. When AARB for six passes, the interface compound very well.3. The recrystallization and ultrafine twins mechanism of six passes AARB copper:Recovering of deformed grains was observed first in the recrystallization annealing of six passes of AARB copper. During the increased of annealing times, the density of dislocation in dislocation cells were reduced greatly, during the crystal mutual migration, polymerization and grain nucleation, some small grains appeared. Further increased the annealing time, obtained some subgrains with low density dislocation, the low-angle boundaries decreased and high-angle boundaries increased with which migrated to the dislocation area of high density.The existence of shear strength changed the atomic stacking fault, it was benefit for the formation of annealing twins. During the recrystallization annealing process, some dislocations of cell wall caused some dislocation extension to the adjacent cell structure within a row of{111} plane and grown up in the migration interface{111} plane accidentally. Shockley partial dislocation contacted with the grain boundaries, the partial dislocations repel each other and slip away from the grain boundaries, then obtained annealing twins. Finally, when annealed at240℃for40min the ultra-fine-grained twin copper was obtained.4. When Six passes of AARB copper annealed at240℃, the low-∑CSL boundaries increased during the increased of annealed time, and reached the recrystallization copper GBDC optimization.5. The mechanical properties, microhardness and electrical conductivity of copper under different conditions were determined and analyzed:during the increased of equivalent strain, the tensile strength increased; the microhardness also increased; the conductivity decreases gradually. When Six passes of AARB copper annealed at240℃for40min, the strength and elongation became very well, the electrical conductivity is equal to the standard annealed state1#Cu and corrosion resistance was much better than original copper.