Experimental investigation into the statistics of pop-ins during nanoindentation of FCC metal Ni and single-crystal ceramic 4H-SIC and 6H-SIC

• Main Author: Goh, Yong Xin
• Other Authors: Upadrasta Ramamurty
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/149458
• Institution: Nanyang Technological University

Due to the growing implementation and interest in nanoscience and nanotechnology, there has been an increase in attention towards the deformation behaviour of materials at the nanoscale lately. It is especially useful for studying the mechanical properties of thin films in the semiconductor industry. Nanoindentation has become a popular technique to measure the mechanical properties of materials, such as their hardness and elastic modulus, which can be obtained from the load-displacement curves. [1] It is also used for the measurements of hardness exponents, creep parameters, and residual stresses. [2] This report presents the results of an experimental investigation and the statistical analysis of the first pop-ins during nanoindentation of single-crystal Face-Centered Cubic (FCC) Nickel and single-crystal ceramics, 4H-Silicon Carbide and 6H-Silicon Carbide. Nanoindentation tests were conducted using three spherical indenters with different tip radii at varying loads and loading rates. The effects of tip radius and loading rates on the yield stress of Ni, 4H-SiC, and 6H-SiC are observed and analyzed. The objectives of this project are experimentally observing the nanoindentation pop-in phenomena, and the statistical analysis on the yielding behaviour in the different materials. The following can be concluded from the results. • For all the single crystals, with increasing tip radius, maximum shear stress decreases, and activation volume increases. • For all the single crystals, with increasing loading rate, there is a general trend of increase in τmax. The overall increase in τmax is lowest in Ni. Hence, loading rate affects the τmax of ceramics more as compared to Ni. • For ceramics, as the loading rate increases, activation volume decreases then increases. The range of differences is greater for 4H-Silicon Carbide as compared to 6H-Silicon Carbide. Also, linearity is better in Silicon carbide samples than in Nickel sample, possibly due to the relatively lower densities of defects in Silicon carbide. • For metals, as the loading rate increase, activation volume increases then decreases. Ni has a larger range of differences in activation volume as compared to ceramics. When comparing the properties between Nickel and Silicon carbides, we observe that pop-in displacement is greater in Ni as compared to Silicon Carbide. Activation volume is also greater for Ni than SiC.