微米尺寸不锈钢的形变与疲劳行为的尺寸效应

采用聚焦离子束溅射蚀刻加工了微米尺寸304不锈钢悬臂梁试样．利用静态及动态弯曲加载研究了微米尺寸材料的形变与疲劳开裂行为．结果表明：随薄膜厚度的减小,材料的屈服强度升高,塑性下降．屈服强度随悬壁梁厚度的变化关系与Hall—Perch晶粒强化关系相似．微小悬壁梁屈服强度的升高来源于小尺度材料在非均匀变形下引起的应变梯度贡献的增加;而塑性下降则归因于较薄薄膜的晶粒内较少的可动位错．疲劳裂纹从尖缺口处萌生的门槛值接近块体材料．

Size Effects On Deformation And Fatigue Behavior Of A Micron-Sized Stainless Steel

Micron-sized cantilever beams of a 304 stainless steel were fabricated by focused-ion beam (FIB). The static bending and dynamic bending tests of the microbeams were carried out. The results show that with decreasing the beam thickness, the yield strength of the microbeam increases and .the ductility decreases. The relation between the yield strength of the microbeam and beam thickness is similar to the Hall-Petch relation of the grain size strengthening. The increase in the yield strength of the thinner microbeam is attributed to the increase in the strain gradient contribution due to inhomogeneous deformation of the small dimensional material. The decrease in the ductility of the microbeam is attributed to fewer mobile dislocations in the grain. The threshold of the fatigue crack initiation from the notch of the microbeam is close to that of the bulk material.