Scanning electro-microscopy of alloys

• Main Author: Koh, Jin Ming
• Other Authors: Shu Dong Wei
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials::Material testing and characterization; Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/141385
• Institution: Nanyang Technological University

Over the years, air travel has gained tremendous popularity due to its efficiency and safety. According to the International Air Transport Association (IATA), in 2016 there were a staggering 3.8 billion air travelers. They predicted that this number will balloon to 7.2 billion passengers by 2035 – nearly doubling of current level. [1] In addition, Deloitte forecasted that in the next two decades, passenger and cargo traffic are expected to grow at an average annual growth rate of 4.6% and 4.4% respectively which in turn increases the production of aircraft. The future of the aerospace industry remains bright and will be characterized by the high demand of aircraft for a foreseeable future. [2] The need for improvements in fuel efficiency and strength of the aircraft parts drives aircraft manufacturers to source for materials that have high strength-to-weight ratio. Aluminum naturally comes into the minds of aircraft manufacturers. They identified its lightweight and ductility properties can be beneficial in the aerospace industry because components used in aircraft need to be very light and have the ability to be molded into any shapes. Also, the fact that aluminum is third most abundant metals in Earth’s crusts – approximately 8.1% of Earth’s total mass, makes it common and affordable as compared to other metals. [3] Other than this, pure aluminum can be combined with other metals, non-metals or elements to form aluminum alloys. This in turn alters and improves the chemical and physical properties. As such, a soft pure aluminum with minimal strength can be altered to provide higher strength. Many of the light aircraft today use Aluminum 6061-T6 alloy in their fuselages and wings. [4] Hence, this project will be carried out to determine if the aluminum 6061-T6 alloys produced by two manufacturing methods have the required strength to be used in the production of aircraft components by conducting in-depth study on the fractography and metallography of its microstructures. The aluminum 6061-T6 specimens were manufactured using two methods namely longitudinal and transverse rolling directions and will undergo a constant strain rate of 0.026mms-1 till failure. In addition, the specimens will also undergo a dynamic compression tests at 15 and 20 m/s. After which, the failed specimen will undergo fractography examination and go through material-prepare (Mat-Prep) processes which includes cutting, mounting, grinding, polishing and etching. The advancement in technology has given rise to precise and accurate imaging devices such as the Scanning Electron Microscopy (SEM) and Optical Microscope (OM). Today, researchers from all around the world have been using the SEM as their main imaging device as the magnification of image and depth of view are far greater than that of OM. Composition, contours and morphology can also be attained when SEM is used. For this project, the prepared specimen’s fracture surfaces and microstructures will be analyzed through the OM and SEM to identify the defects such as micro-voids and –cracks so as to determine which specimens display more strength. With this information, we can identify which manufacturing method is preferable. The images and data obtained will be compared to existing results and images from established sources to validate the results.