Tensile deformation behaviors of pure nickel fine wire with a few grains across diameter
(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)
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