(1. 哈爾濱工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，哈爾濱 150001；
2. 哈爾濱工業(yè)大學(xué) 微系統(tǒng)與微結(jié)構(gòu)制造教育部重點實驗室，哈爾濱 150080；
3. 哈爾濱工業(yè)大學(xué) 基礎(chǔ)與交叉科學(xué)研究院，哈爾濱 150080；
4. 哈爾濱工業(yè)大學(xué) 機(jī)電工程學(xué)院，哈爾濱 150001)
摘 要: 研究純鎳絲材單向微拉伸塑性變形過程中的流動應(yīng)力和非均勻變形行為尺寸效應(yīng)。實驗發(fā)現(xiàn)，流動應(yīng)力隨晶粒尺寸的增加(或直徑方向上晶粒數(shù)量的減少)而降低，而非均勻變形程度增加。當(dāng)直徑方向上少于9.3個晶粒時，流動應(yīng)力隨晶粒尺寸增加而快速降低。通過引入晶界尺寸因子構(gòu)建介觀尺度材料本構(gòu)模型揭示絲材微拉伸流動應(yīng)力尺寸效應(yīng)。結(jié)果表明，斷裂應(yīng)變和斷裂應(yīng)力隨著晶粒尺寸的增加而減小。當(dāng)試樣直徑方向上少于14.7個晶粒時，斷裂應(yīng)變和斷裂應(yīng)力快速降低，表明微拉伸過程中的非均勻變形程度隨著直徑方向上晶粒數(shù)量的減小而增加。當(dāng)試樣直徑方向上的晶粒數(shù)量減少時，斷口形貌變得越來越不規(guī)則。從材料微觀組織分布方面分析了不規(guī)則斷口形貌的形成機(jī)理。
關(guān)鍵字: 鎳絲；尺寸效應(yīng)；微拉伸；流動應(yīng)力；非均勻變形；斷裂
（1. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
2. Key Laboratory of Micro-systems and Micro-structures Manufacturing, Ministry of Education,
Harbin Institute of Technology, Harbin 150080, China;
3. Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, China;
4. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China）
Abstract:Size effects on plastic deformation behaviors in uniaxial micro tension of pure nickel fine wires were investigated experimentally, including flow stress and inhomogeneous deformation behaviors. It is found that with the increase of grain size or the decrease of number of grains across the diameter, the flow stress decreases and inhomogeneous deformation degree increases. When there are less than 9.3 grains across the diameter, the flow stress decreases quickly with the increase of grain size. Then, the flow stress size effect in micro tension of fine wires is revealed by a proposed model by introducing the grain boundary size factor. These results also indicate that both the fracture strain and stress decrease with the increase of grain size. When there are less than 14.7 grains across the diameter, both the fracture strain and stress decrease quickly. This indicates that the inhomogeneous deformation degree in micro tension increases with the decrease of the number of grains across the diameter. The fracture topography tends to be more and more irregular with the decrease of the number of grains across the diameter. Then, the formation mechanism of irregular fracture topography was analyzed considering the inhomogeneous distribution of microstructure when there are a few grains across the diameter.
Key words: nickel wire; size effect; micro tension; flow stress; inhomogeneous deformation; fracture
