SEM analysis of high strain tested specimens

• Main Author: Muhammad Syafiq Shamsuri.
• Other Authors: Shu Dong Wei
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/50029
• Institution: Nanyang Technological University

Lightweight materials have been in focus in recent times for their use in automobiles, planes and protective structures for numerous benefits ranging from reduction in fuel consumption and increased payload in vehicles to lighter and stronger protective structures. For efficient use of materials in applications where they are subjected to unusual higher sudden loads, it is necessary to understand their mechanical behaviour under such conditions. In this project, the effect of strain rate on deformation of magnesium alloy AZ31B under compression has been investigated as well as the effect of temperature. The alloy is subjected to various strain rates such as 10-4/s, 500/s and 2500/s, and temperatures of -30oC, 25oC and 200oC. A collision test of AZ31B magnesium alloy was conducted to investigate the effect of the compression as well as temperature in order to relate the stress-strain characteristics of the samples. Samples which are attained from the collision test of AZ31B are then being analysed by observing the changes in microstructure through the use of the Optical Microscope (OM) as well as Scanning Electron Microscope (SEM). Material composition of the microstructure is identified by using the Energy-dispersive X-ray spectroscopy (EDX). Sample preparation are done using the methods of 1)cutting, 2) grinding, 3) moulding, 4)polishing and 5)etching. Microstructure images are collected and compared in order to understand the relation of strain effect and temperature effect on the AZ31B magnesium alloy. Microstructural analysis was performed to see the changes in the microstructure of the alloy and their effect on the mechanical response of the alloy is portrayed. Microstructural analysis was done for specimens of various orientations such as angular, normal, transverse and rolling directions in order to study their behaviour. As the strain rate increases, it was observed that there was a refinement in the grain boundaries of the alloy and micro structural twins are becoming less significant. Shear bands, micro-cracks, elongated and broken grains are also visible at higher strain rates.