塑性流动挤出切削制备梯度结构铝薄板的仿真分析

Simulation analysis of aluminum sheets with gradient structures produced by plastic flow machining

塑性流动挤出切削(plastic flow machining,PFM)工艺是一种新型的大塑性变形(severe plastic deformation,SPD)工艺,所制备的铝薄板沿厚度方向呈现明显应变梯度,且晶粒尺寸由一侧的超细晶粒逐渐过渡到另一侧的粗大晶粒。这种梯度结构铝薄板兼顾了高强度与高塑性,具有很好的应用前景。在PFM工艺中,模具结构对梯度结构薄板成形起到了关键甚至决定性的作用,但目前缺少相关研究。采用控制变量法,通过有限元模拟不同模具结构下梯度结构铝薄板的成形。结果表明,梯度结构铝薄板的侧向挤压比x、左侧等效应变ε_(L)及右侧等效应变ε_(R)均与模具的开口圆角R及挤压角度C的取值密切相关,且x随着R及C的增大而减小。此外,当R为1.5 mm、C为120°时,ε_(R)与ε_(L)之差最大。

Plastic flow machining(PFM)is a new process of severe plastic deformation(SPD).The aluminum sheets produced by PFM show obvious strain gradient along the thickness,and the grain sizeof them gradually changes from ultrafine grain on one side to coarse grain on the other.This kind of aluminum sheets with gradient structures have both high strength and high plasticity,which have a great application prospect.The die structure plays a crucial and even decisive role in the forming of gradient-structural sheetsproduced by PFM,but so far there is no few relevant research.In this paper,the control variates method is used to simulate the forming of aluminum sheets with gradient structures under different die structures by finite element method.The result shows that the lateral extrusion ratio x,the left equivalent strainε_(L) and the right equivalent strainε_(R) of the aluminum sheets with gradient structures are closely related to the value of the opening rounded corner R and the extrusion angle C of the die,and x decreases with the increase of R and C.In addition,when R is 1.5 mm and C is 120°,the difference betweenε_(R) andε_(L) becomes the largest.