Development of Aluminium Composite and its Foams for Mechanical Applications

Abstract

The present work contains the details and discussion on the development and characterization of zircon sand reinforced LM13 aluminum matrix composites (AMCs) and LM13 aluminium matrix foam (AMFs) and its composite (AMCFs). The entire work in this thesis is presented in seven chapters. In the chapter 1, general introduction to particle reinforced aluminium matrix composite is given. A summary of particle reinforced aluminum matrix composite, aluminum foam and aluminum composite foam along with their production methods are also presented in this chapter. The main factors responsible for the mechanical properties of the AMCs, AMFs and AMCFs along with their properties and applications in different sectors are also discussed in brief. Chapter 2 covers the literature review regarding the work done on the development of AMCs, AMFs and AMCFs by many researchers using different fabrication techniques and their study based on wear behavior. As our work is based on the stir casting process, hence we focus on the works done by the researchers in the related area for development of AMC, AMF and AMCF and their physical properties, hardness, wear resistance and blast mitigation. The last section of this chapter presents the aims and plan of the work of the thesis. Chapter 3 contains the experimental procedure followed in the present work. Detailed procedure to develop the AMCs, AMFs and AMCFs and their characterizations are given in this chapter. Different characterization techniques such as X- ray diffraction (XRD), Optical microscopy, Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Vickers hardness testing and Wear testing with pin-on-disc machine and blast mitigation test along with different operating parameters are also discussed. A flow chart of the methodology used to develop for AMCs and AMF/AMCFs are also given in this chapter. xvii Chapter 4 deals with microstructural analysis and discussions of developed AMCs, AMFs and AMCFs. The structural analysis of the developed AMCs, AMFs and AMCFs with reinforcement of different size zircon sand particles in the alloy matrix at different conditions has been done critically. Al-Si alloy (LM13) was used as the matrix material for the composites. Composites with reinforcement 2.5- 15wt.% (average particle size range fine (1- 32 μm) and coarse size (106- 125 μm) were prepared. Optical microscopy and SEM were used to examine the distribution of reinforced particles in the matrix of AMCs and AMCFs. In this chapter, results of microhardness and wear tests obtained from cast AMCs, AMFs and AMCFs is discussed. Reinforcement of fine (1-32μm) and coarse (106-125μm) size ZrSiO4 particles from 2.5- 15 wt.% have been used to develop AMCs and AMCFs. The particle bonding with matrix was tested by measuring hardness at the interface. Wear behavior with variation in applied load of fine and coarse size ZrSiO4 particles reinforced composites is described in this chapter. The results show that wear characteristics of the AMC-15Cfine, AMF-2F900 and AMCF-15Cfine is better than other developed AMCs, AMFs and AMCFs. The operative wear mechanism has been established by analyzing the wear track and wear debris under scanning electron microscope. The overall results of all the developed samples have also been discussed at the end of the chapter. Chapter 5 gives the details of the blast mitigation test of AMFs and AMCFs. The effective range of blast pressure depends on the density and cell geometry of the AMFs and AMCFs. Blast mitigation test were performed on AMFs and AMCFs samples prepared by using different wt. % of blowing agent (for AMFs) and ZrSiO4 reinforcement (for AMCFs). Blast mitigation trials were conducted using CE pellet having 35g of tetryl charge. The results of the blast tests and their failure study of deformed materials done on developed foams in Terminal Ballistics Research Laboratory, Defence Research and Development Organization, Ramgarh, Chandigarh, India have been compiled and discussed. xviii Chapter 6 describes the conclusion of the entire work done in the present investigation along with the future scope. The present work shows a good distribution of the zircon sand particles in LM13 alloy matrix developed by stir casting process. XRD data shows the presence of zircon sand particles as well as new phase developed during the casting process. Uniform distribution and bonding of zircon sand particles with the matrix was observed. It was found that hardness of the base alloy was improved with increasing the amount of zircon sand particles in the matrix. However, with decreasing the particle size hardness of the composites was increased significantly. Wear tests of all the developed composites were done at different loading conditions. It was observed that wear resistance of the base alloy improved with increasing the amount as well as decreasing the size of the reinforced particles. However, wear rate of the composites increases with increasing the applied load. In case of AMFs and AMCFs factors which are affected by the foaming temperature on alloy foam and composite foams were investigated. It was found that the foaming temperature for alloy foam and composite foams influence the cell geometry which ultimately generates different structures. Addition of zircon sand particles influences the foaming temperature and viscosity for the internal diffusion pressure of the melt material. The optimized condition of foaming temperature for composite foam containing 5wt.% zircon sand and alloy foams are 875 ºC and 850 ºC respectively when 2wt.% CaCO3 as foaming agent having narrow particle size (1-32μm) has been used. Cell size of the sample foamed increases with increasing particle size of blowing agent. By properly controlling the foaming temperature and zircon sand content of the melt, which is different for alloy and composites, it is possible to optimize the condition to get uniform size foams having high porosity. The increase in foaming temperature and gas flow rate enlarge the cell size and decrease the cell wall thickness due to the difference pressure between cell wall and node. AMCF-15Cfine shows better wear resistance in comparison to all AMFs and AMCFs at different applied loads.