Semi-solid Powder Rolling of AA7050 Alloy Strips: Densification and Deformation Behaviors

Abstract

Semi-solid powder rolling (SSPR) is a novel strip manufacturing process which combines the features of semi-solid rolling and powder rolling. SSPR involves rolling procedure of metallic alloy powders when both liquid and solid phases coexist. In this study, densification process and deformation mechanisms of AA7050 powder in the presence of liquid phase were investigated. The relationships between the apparent plastic Poisson's ratio and the relative density as well as the thickness reduction ratio and relative density were calculated. The relationship between deformation strain and relative density was calculated as well. The experimental data of relationship between rolling forces and relative density were achieved. The results show that the densification process of SSPR also can be divided into three stages and liquid phase mainly affects stage I. In stage I, semi-solid particles' rearrangement and restacking are the main densification mechanisms when the initial liquid fraction is lower than 20 pct. When the initial liquid fraction is higher than 20 pct, flowing and filling of liquid, semi-solid particles rearrangement and restacking are the densification mechanisms. In stage II, severe deformation of particles associated with a rapid increase in the apparent plastic Poisson's ratio and interparticle contact area contributes to the densification process. In stage III, the densification mechanisms are the deformation and collapse of isolated pores. The calculated deformation strain increases gradually with the same slopes as the relative density increases in stages II and III no matter how much the liquid fraction is. Higher liquid needs less deformation degree that contributes to the densification.

Synergetic effect of milling speed and duration on particle morphology and mechanical properties of nanocrystalline Al matrix containing SiC

“…Moreover, the consolidation by plastic deformation, such as powder rolling [17][18][19] and sheath rolling [20,21] of as received metal powder or low energy ball milled powder, was investigated by many researchers. It has been seen from the literature that there is no significant improvement in the mechanical properties of sheath-rolled Al/Al 2 O 3 [20] and Al/SiC [22] metal matrix composites.…”

Deformation behavior and forming process simulation of semi-solid powder rolling based on the combined constitutive model

“…The numerical simulation is the best method to study the forming process of SPF but the present simulated constitutive relationships were mostly obtained from dense or porous materials [7,[11][12][13]. However, the material during SPF changes from discontinuous semi-solid particles with an apparent relative-density of 30%-50% into a continuous porous solid body with a relative-density of 90%-100% [14,15]. Single constitutive model of dense or porous materials cannot well meet the actual forming situations of SPF.…”