Mesomechanics Simulation Of Pure Zr Processed By Mutipass Of ECAP

The pure Zr was processed by one pass of ECAP using a die with the internal angle of 90° at room temperature. Measuring and testing techniques such as optical microscope（OM）, transmission electron microscope（TEM）, scanning electron microscope（SEM）, X-ray diffraction（XRD） and so on, were used to analyze the microstructure and texture evolution. Based on the data of one pass of ECAP from electron back scattering diffraction（EBSD）, texture evolution was simulated with the help of ABAQUS and VPSC. Texture prediction of two passes of ECAP was carried out by VPSC. The pole figures and ODFs were obtained by MTEX.The results of microstructure evolution show that most of coarse grains are broken and the dislocation density increases dramatically after one pass of ECAP. Meanwhile, lots of dislocation tangles and shear bands can be observed. The results of tensile test, microhardness and SEM show that the yield strength, ultimate tensile strength and microhardness increase simultaneously while the ductility is good enough. The analyses of XRD indicate that the typical bimodal base texture of as-received pure Zr disappears and B texture and C₂ texture are formed after one pass of ECAP. And B texture and C₂ texture rotate a certain angle around TD axis. Based on extended Taylor model and VPSC model, the texture evolution simulations of one pass of ECAP were implemented at room temperature. The initial texture evolves into C₁ texture and C₂ texture with the Taylor model, and the results of VPSC model agree with the experimental results. On the basis of one-pass simulation, the texture evolution of second pass with route C was predicted using the VPSC model at room temperature. The results show that C₂ texture disappears basically and develops into B texture. But the pole density does not change obviously due to the limited number of grains. Under the shear stress state, the schmid factors show that the bimodal texture activates pyramid-<c+a> slip system accompanying with tensile twin and compression twin. B texture and C₂ texture formed during the one pass of ECAP activate prism-<a> pyramid-<a> slip systems and compression twin. B texture obtained by prediction activates pyramid-<a> slip system and compression twin.