螺旋通道长度对纯铝粉末多孔材料等径角挤扭变形的影响

针对等径角挤压和挤扭两种工艺的不足,在充分发挥各自优势的基础上,提出了一种新型的大塑性变形工艺——等径角挤扭(Equal Channel Angular Pressing and Torsion,ECAPT)。采用DEFORM-3D软件对纯铝粉末多孔材料等径角挤扭成形过程进行单道次三维有限元模拟,重点分析螺旋通道长度对变形试样挤压载荷、等效应变、致密行为等场量变化规律的影响。结果表明,相比于传统的ECAP变形,ECAPT工艺螺旋通道的存在,可大大增加变形试样内部的静水压力;合理的螺旋通道长度,可有效提高变形试样的累积应变量和应变分布均匀性,显著改善变形试样的整体致密效果。文章在综合考虑最优数值模拟结果的基础上,自行设计了螺旋通道长度为30mm的ECAPT模具,并进行了相关实验验证,证明了所建立有限元模型的可靠性。

Effect of length of twist channel on porosities of pure aluminum powder during equal channel angular pressing and torsion

A new type severe plastic deformation technique was developed to improve the non-uniformity and discontinuity of deformed billet.This novel technique,named equal channel angular pressing and torsion(ECAPT),combines two severe plastic deformation methods:equal channel angular pressing and twist extrusion.The effect of length of twist channel on porosities of pure aluminum during a single pass of ECAPT was investigated by using three-dimensional finite element method.The pressing load,effective strain distribution and relative density of deformed billet were also analyzed.It is indicated that compared with the conventional ECAP,the hydrostatic stress of deformed billet was largely increased due to the existence of twist channel.Imposing appropriate length of twist channel is helpful to increase the effective strain of the billet and to improve its deformation homogeneity and relative density as well.ECAPT experiment with 30 mm long twist channel has been carried out and the reliability of the established finite element model is verified.