Grain Size Effect on the Nanomechanical Properties and Deformation Mechanisms of Copper

• Main Authors: Ting-Kui Chang, 張庭魁
• Other Authors: Shou-Yi Chang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/03908963965482226685

碩士 === 國立中興大學 === 材料工程學系所 === 94 === In the study, the mechanical properties and deformation behaviors of copper with different grain sizes have been investigated by instrumented nanoindentation. For the copper specimens with large grain sizes, hardness was found to increase with decreasing grain size, from 1.0 GPa increase to 2.3 GPa, following the “Hall-Petch relation”. Dislocations were clearly observed in the deformed regions around indent marks, indicating the plastic deformation by dislocation formation and sliding. However, the hardness of electroless copper films with an ultrafine grain size of about 10 nm dropped to 1.0 GPa. Voiding at grain boundaries and triple grain junction was observed as a consequence of grain boundary sliding and grain rotation which were expected as the dominant deformation mechanism and resulted in the hardness decrease. The critical shear stresses for the initiation of plastic deformation in the copper specimens with large grain sizes were close to the theoretical value of 1.3 GPa, but however it was much lower for the electroless copper films with an ultrafine grain size. Fast diffusion paths through the large amounts of grain boundary lead to a more large creep rate.