Large Deformation Asynchronous Arb Prepares The Microstructure And Properties Of Ultrafine Grain Copper

Grain refinement is an effective method to improve the intensity of materials. Superior to the traditional pile rolling, severe plastic deformation with Asymmetrical Accumulative Roll-bonding (AARB) has strong ability to refine grain and improve the precision rolling method of the products greatly because of its machining process. So AARB has a great extent of application prospects.In the paper, the present state of ultra-fine-grained materials, severe plastic deformation and Asymmetrical-ARB are introduced in detail. Utilizing the analysis methods of Optical Microscopy, Scan Electron Microscopy, Transmission Electron Microscopy, Atomic Force Microscopy and mechanical properties testing, we have studied that microstructure's change in materials had effect on mechanical properties in the process of AARB;recrystallization annealing had a significant role of preparing ultra-fine grain copper and the change of microstructures and properties. On base of having prepared ultra-fine grain copper, we have studied its microstructures and properties.Studies have shown:1. After six passes by AARB, materials' σ_0.2 has rised from 101.5MPa to 349.6MPa, σ b has rised from 231.3MPa to 455.7MPa,microhardness has rised from 63.0HV to 110.7HV, but the percentage elongation drop seriously.2. After six passes by AARB and recrystallization annealing at 220℃ for 35min,we have prepared ultra-fine grain copper with well microstructure and the size of grain is between 100 and 200nm.Its σ)( 0.2) is 318.8MPa, σ_b is 420.8MPa , the microhardness is 123.0 HV, fracture elongation is 7.20% and the ductibility is well.3. The relation between grain size and mechanical properties in the ultra-fine grain copper was still accord with Hall-petch relation, and microstructure defect influenced its plasticity strongly.4. Fracture mechanism of the ultra-fine grain copper is plastic fracture mostly and brittle fracture little.5. In condition of different deformation ,the grain size of ultra-fine grain copper after rolling was not changed, σ_0.2 and microhardness were increased and percentage elongation was reduced.