Effect of cold-work on the Hall–Petch breakdown in copper based micro-components

• Main Authors: Ghassemali, Ehsan, Tan, Ming-Jen, Wah, Chua Beng, Lim, S.C.V., Jarfors, Anders E.W.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2016
• Subjects: Microforming; Subgrain; Microstructure; Size effect; Dislocation cells
• Online Access: https://hdl.handle.net/10356/81567; http://hdl.handle.net/10220/39595
• Institution: Nanyang Technological University

Effects of substructural dimensions on the mechanical properties of micro-pins produced by an open-die micro-extrusion/forging process were studied. Micro-pins of diameter 0.3 mm were manufactured from copper strips, having different initial grain sizes. Micro-compression tests on the micro-pins revealed no significant size effect, even if the number of grains over the diameter of the micro-pins falls below its critical value. However, relaxation of the as-formed substructure using recovery annealing led to a surprising drop in the flow stress of the micro-pins. This was explained and attributed to the number of subgrains over the diameter of the micro-pins, showing the important role of subgrains rather than grains in determining the mechanical properties.