5052铝合金板材磁脉冲动态拉伸塑性失稳分析

PLASTIC INSTABILITY ANALYSIS OF 5052 ALUMINUM SHEETS IN MAGNETIC DYNAMIC TENSION PROCESS

为揭示磁脉冲成形的增塑机制,采用理论分析与微观组织观察相结合的方法对5052铝合金板材磁脉冲动态拉伸过程中动态成形行为和塑性失稳机制进行了系统研究.结果表明,惯性力在动态成形中起主要作用,惯性力对试样的结构失稳具有抑制作用,从而使试样的塑性提高并产生分散失稳;5052铝合金动态成形和准静态成形的成形性质相似,不会产生特殊的组织结构,塑性变形机制均为位错滑移机制;准静态成形过程以均匀单系位错滑移为主,断裂伴随着位错的缠结和攀移;而动态成形过程中,位错滑移趋于多系开动,在大面积区域出现明显的交滑移现象,且滑移带较准静态成形时窄且密,位错组态更均匀;动态成形的多系滑移和位错均化作用可在比准静态成形高的多的塑性应变水平下形成,从而使材料表现出较高的塑性和强度.

In order to reveal the hyperplasticity mechanism of electromagnetic forming（EMF）, the plastic instability mechanisms and formation behaviors of 5052 aluminum alloy sheets in pulsed magnetic tension process were investigated by theoretical analysis and microanalysis.Results show that inertia force plays an important role in dynamic forming,which has the suppression effect on structural instability and thus improves the formability of sheet and spreads instability.The nature of dynamic formation is much similar with that of quasi-static formation and no special formation structures arise in dynamic process for 5052 aluminum alloy sheets.The formation mechanism of both processes is dislocation slip mechanism.For quasi-static formation,the dislocations show a uniform single-slip pattern,fracture combined with dislocation tangling and climbing.While for dynamic formation, dislocation system tends to more slips,large areas showing clear cross-slip structures.The dislocation bands are narrower and much denser than those shown in the quasi-tatic process,and a much more uniform dislocation configuration is also exhibited after pulsed magnetic loadings.The characteristics of multi-slips and uniform effect of dislocations under pulsed magnetic loading conditions will result in much higher plasticity and strength of materials.