金属箔材轧制过程中第二相颗粒的尺寸效应研究

The size effect of different types of secondary particles in metallic foils during its foil rolling process

金属箔材轧制时,箔材的厚度最小为几个微米.微米级甚至是亚微米量级尺寸的第二相颗粒都可能对基体的力学性能,甚至是箔材的表面形状造成影响.相对于基体而言,颗粒的软硬程度及其大小对轧制过程中箔材的影响是截然不同的.该文通过有限元模拟的方法研究了单个的硬质及软质第二相颗粒对箔材基体性能及形状的影响.论文中引入参量:颗粒直径/箔材厚度比(以下简称d/T).结果表明,箔轧时,相较于硬质颗粒而言,不同尺寸的软质颗粒对箔材的影响较大.第二相颗粒为软质颗粒时,应力集中程度及箔材表面变形程度随着颗粒尺寸的增大而增大,当d/T小于1/20时,第二相颗粒周边基体应力集中现象不明显;当d/T为1/20~1/5时,应力集中比较明显,箔材表面发生轻微变形;当d/T大于1/5时,基体中应力集中明显,箔材表面变形严重.第二相颗粒为硬质颗粒时,随着d/T的增加应力集中现象越不明显,基体表面几乎没有变形.

In foil rolling, the minimum thickness of metallic foils is usually several microns, while the size of the secondary particles in alloys is from several nano-meters to tens of microns. It is necessary to know the effect of hard and soft particles in different sizes on stress concentration and the shape of the foil surface in the foil rolling process. In this study, a parameter of particle diameter to foil thickness ratio has been introduced. Finite element simulation was used to investigate the effect of this parameter on the mechanical properties and the shape of the foil surface. It is found that for soft particles when the d/T is less than 1/20, the second particles result in a slight effect on stress concentration of its surrounding matrix and foil surface shape. When d/T is in 1/20～1/5, the stress concentration caused by the secondary particle is dramatic, and the surface shape change of foil is observed. When this ratio is over than 1/5, severe stress concentration and surface shape distortion occurs. For hard particles with the increment of d/T,the second particles have nearly no effect on stress concentration of its surrounding matrix and foil surface shape.