Investigatinng Of The Structure Of Bulk Ultrafine-Grained Material Prepared By Equal Channel Angular Pressing (ECAP)

Equal channel angular pressing technology (ECAP) provides an effective procedure for obtaining the bulk sub-micrometer or nanometer scale materials by sever plastic deformation. However, the best process has not been found in technique since the structural homogeneity of the ultra-fine grained materials depends on the applied technologic processes and the original structures of materials and so on.An overall investigation on the choices and optimization of technologic parameters for different materials is still lacking. And the mechanisms of grain refinement need to be put forward further.According to the fundamental theories and the latest research progress, we analyze systematically the influences on microstructures and properties of the ultra-fine grained materials caused by technologic parameters such as structure and dimensions of ECAP dies, the number of pressing ,the routes of ECAP, the velocities , temperature and the friction states of the ECAP.Al-5Ti-B alloy, one kind of grain refiners for aluminum and aluminum based alloys, was used as the experimental object of ECAP experiment. By the experiment the optimizing technologic parameters were determined and the corresponding die was designed and manufactured. By performing the experiments in different technologic processes, we observed the changes of microstructures and properties, measured the stress-strain curves and beat out the influences of technologic parameters on microstructures and properties in the deformation. Then the evolution of ultra-fined structures of the object was discussed in the experiment.Meanwhile, the deformation and the structural evolution in the ECAP were...