介观尺度磷青铜薄板韧性断裂和变形行为的尺寸效应

借助单轴微拉伸试验研究了磷青铜薄板力学性能和韧性断裂的尺寸效应。结果表明，屈服强度与材料厚度t、晶粒尺寸d之间均存在着第Ⅱ类尺寸效应，但与t/d之间却存在着第Ⅰ类尺寸效应。断口形貌显示，随着t的减小，断裂机制由韧窝-微孔聚集断裂向滑移分离过渡；随着d的增大，韧窝逐渐变大变深，但当t/d<1时，拉伸过程过早形成微裂纹，导致试样迅速断裂。最后，基于表面层模型构建了介观尺度磷青铜薄板的混合本构方程。

Size Effects of Deformation Behaviour and Ductile Fractures in Meso-scale Thin Sheet Metal of Phosphor Bronze

Size effects of mechanics properties and ductile fractures for ultra thin sheet metal of phosphor bronze sheet were studied by uniaxial micro tensile test. Experimental results show that yield strength has second order size effeets with metal thickness t and grain size d， and has first order size with t/d. Fracture surface shows that the fracture mechanism is composed of transitions from dimple-microvoids accumulation fractures to slip separation with the material thicknesses decrease, and dimple morphology becomes larger and deeper with the increases of grain sizes, but when t/d＜1, initiation of micro cracks is geminated, and fracturs are occurred immediately. At last, a hybrid constitutive equation was established based on surface layer model.