Papers by Author: Yu Xuan Du

Abstract: Void growth in aluminum single crystals is simulated using the finite element method, to illustrate the effect of grain orientation on void growth, a rate dependent crystal plasticity constitutive theory is implemented as a user-defined plasticity subroutine. A three-dimension unit cell including a sphere void was employed using three-dimensional 12 active slip systems. The computed results for several grain orientations are compared, which have shown that crystallographic orientation has significant influence on growth behavior of void. And the void growth direction and shape significantly depend on the crystallographic orientation. Due to plastic flow localization and anisotropic behavior, void which has an initial sphere shape, develops an irregular shape and some corners.

Abstract: Grain refinement of 01420 Al-Li alloy through particle stimulated nucleation(PSN) of recrystallization is reported. The results showed that the rolling in the overaged 01420 Al-Li alloy resulted in the formation of the deformation zones associated with the second phase particles larger than 0.80 μm which can act as the nucleation sites for recrystallized grains. The precipitates larger than 0.80 μm are sticked shaped S-phase(Al2MgLi) and globular β-phase(Mg2Al3), and the density of β-phase particles is approximately as two to three times as the S-phase particles. The S-phase particles can’t be as PSN sites since they were broken to small dispersoid particles during rolling. The average grain size of 01420 Al-Li alloy solutioned at 470°C for 2h, aged at 300 °C for 48h, 81% rolled at 300 °C and finally recrystallized at 500 °C for 10min is approximately 10 μm.

Abstract: A novel shear-deformation technique, named ‘shear pressing’ (SP), was developed for fabrication of plate-shaped fine grained metallic materials. The principle of SP is that a material is subjected to shear deformation by utilizing pressing with inclined plane dies. A micrometer order grain structure was obtained in an Al-Mg-Li alloy at strain of ε = -2.3 by utilizing this technique. The grain refinement sequences during pressing were examined by electron backscatter diffraction. The enhancement of grain refinement to the Al-Mg-Li alloy was compared with plane strain compression (PSC) at similar strains. The effect of the shear strain on the accelerated grain refining during compressing has been discussed.