Texture evolution and grain refinement of ultrafine-grained copper during micro-extrusion

Samples of oxygen-free high conductivity (OFHC) coarse-grained (CG) and ultrafine-grained (UFG) copper were micro-extruded to an equivalent strain of 2.8 in one pass at room temperature. Samples of the OFHC copper were annealed at 650°C for 2?h to produce CG copper. Some samples were subsequently processed by equal channel angular pressing of eight passes, route Bc, at room temperature to produce the UFG material. Crystallographic texture and misorientation distributions were obtained locally from EBSD mappings at different radial positions after micro-extrusion. To model the strain path during micro-extrusion, the analytic flow line model of Altan et al. [J Mater. Process. Tech. 33 (1992) p.263] was used and also validated by finite element calculations. Modelling was carried out using the viscoplastic self-consistent (VPSC) model and a recently developed grain refinement model. The results showed large texture variations along the cross-section of the extruded sample for both UFG and CG copper. These cyclic drawing textures in UFG copper were simulated in good agreement with experiments using the presented modelling framework.     

3003铝合金激光冲击微挤压成形研究

微挤压模约束下的激光冲击微体积成形技术是利用激光诱导的冲击波使局部金属在凹模约束下产生体积变形的一种成形新技术。为了分析不同板厚(0.12mm,0.15mm,0.17mm和0.22mm)的3003铝合金在不同凹模孔径(0.4mm,0.7mm,0.9mm和1.1mm)约束下的成形深度,采用建立有限元模型进行数值分析的方法,进行了理论分析和实验验证,取得了不同板厚和不同孔径成形下成形深度的数据。结果表明,成形深度随板厚的增大而增大趋势逐渐减小;对于同一厚度,板料成形深度随孔径的增大呈非线性增大趋势;对于同一点冲击,冲击次数对板料的成形深度影响很大。数值分析结果与实验吻合度较好,这一结果对微体积成形质量控制是有帮助的。