AN ASSESSMENT OF THE MECHANICAL PROPERTIES OF THE ALUMINUM BRONZES

Description

This work studied the assessment of the mechanical properties of the aluminium bronze. Despite some of the desirable characteristics most aluminium bronze exhibits, terribly deficient responses in certain critical applications necessitate mechanical properties enhancement. Hence, the microstructure and mechanical properties of cast aluminium bronze reinforced with iron granules (millscale) were investigated in this paper. Cast samples of the composite made from metal mould contain millscale in varied amount from 2-10 wt.%. The samples were homogenised at 1100⁰C for 10 minutes in order to relief the as-cast structures. Standard specimens were prepared from these homogenised samples for tensile, charpy impact and microhardness tests while the composite microstructures were studied using an optical microscope. Results show that optimum improved mechanical properties were achieved at 4 wt.% millscale addition with ultimate tensile strength (UTS) of 643.8MPa which represents 10.1% improvement over conventional aluminium-bronze. The composite also demonstrated impact resilence of 83.9J and micro-hardness value of 88.7HRB. Millscale presence in the aluminium bronze system induced a stable reinforcing kappa phase by nucleation mechanism which resulted to enhancement of mechanical properties. However, the composite properties were impaired on millscale addition above 4 wt.% due to grain clustering.

 

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• AIM AND OBJECTIVE OF THE STUDY
• SCOPE OF THE STUDY
• LIMITATION OF THE STUDY
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF ALUMINIUM BRONZE
• COMPOSITIONS OF ALUMINIUM BRONZES
• MATERIAL PROPERTIES OF ALUMINIUM BRONZES
• APPLICATIONS OF ALUMINIUM BRONZES
• FABRICATION AND HEAT TREATMENT OF ALUMINIUM BRONZE

CHAPTER THREE

METHODOLOGY

• EXPERIMENTAL PROCEDURE
• SPECIMENS’ PREPARATION AND TESTS
• MICROSTRUCTURAL ANALYSIS

CHAPTER FOUR

4.0      RESULTS AND DISCUSSION

• MICROSTRUCTURE
• TENSILE STRENGTH
• IMPACT ENERGY
• DUCTILITY RESPONSE
• MICROHARDNESS

CHAPTER FIVE

• CONCLUSION
• REFERENCES

 

 

CHAPTER ONE

1.0                                                                      INTRODUCTION

1.1                                                         BACKGROUND OF THE STUDY

Aluminium bronzes are copper based alloys with aluminium as the major alloying element usually in the range 5% – 14% compositionally in the alloy, other alloying elements sometimes intentionally introduced are iron, nickel, manganese, silicon and tin depending on the in- tended application of the aluminium bronze.

Aluminum bronze is very useful in a great number of engineering structures with a variety of the alloy finding applications in different industries (CDA, 1986). According to ISO 428 specifications, most categories of aluminiium bronze contain 4-10 wt.% aluminium in addition to other alloying agents such as iron, nickel, manganese and silicon in varying proportions. The relatively higher strength of aluminium bronze compared with other copper alloys makes it suitable for the production of forgings, plates, sheet, extruded rods and sections (Pisarek, 2007). Its excellent corrosion resistance property recommends it as an important engineering material for highly stressed components in corrosive environments (www.morganbronze.com. The alloy is available both in wrought and cast forms and is readily weldable and fabricated into components such as pipes and pressure vessels. Despite these desirable characteristics most aluminium bronze exhibit deficient responses in certain critical applications such as in sub-sea weapons ejection systems, aircraft landing component and power plant facility. The need to overcome obvious performance limitations in aluminium bronze is imperative to meet today emerging technologies.

This will help to extend the frontier of usage and provide the platform to fully harnessed the potentials and versatility of aluminium bronze apllications in aircraft, petrochemical and offshore components. The feasibility of the foregoings hinges on microstructural modification of the alloy such that relevant physical and mechanical properties improvement are achieved (Yang, et al.,2011). Structure modifications in aluminium bronze are often accomplished through any or a combination of the following processes namely; alloying, heat treatment and deformations. The choice of method however is usually determined by cost and effectiveness. The mechanical properties of aluminium bronze apart from aluminium depend on the extent to which other alloying elements modify the structure. In this regard, iron has been found to be both effective and efficient grain refiner in aluminium bronze systems. The presence of iron in the system enables the inducement of a hard reinforcing phase, CuAl10Fe_3, in proportion to the amount of iron and other alloying agents. According to Oh-Ishi and McNelley (2004), this structure has proven to be responsible for the significant improvement in tensile strength while other desirable properties are not compromised. Cenoz, (2010) also observed that the addition of Fe in the aluminium bronze system in varying amounts may cause just a small change in the transformation products but will definitely contribute significantly to the refinement of the structure. Modification of structure predicated on iron addition affects both the size and morphology of phases (Hassan, et al. 1985). In particular, the precipitation of different stable α, and β phases with intermetallic precipitates of Al₃Fe, Al₅Fe₂ and Al₁₃Fe₄ (depending on both the quantity of Fe in the system and other processing conditions) impact significantly the alloy mechanical chacteristics. Iron (Fe) granules can be cheaply obtained in commercial quantity from its generic oxide for the purpose of alloying same with aluminium bronze. Granulated iron oxide, commonly called millscale is usually formed on the surface of hot rolled profiles such as plates, sheets, bars, etc. Millscale formation invariably represents a significant level of yield loss to millers as it often reflects in huge differences between input stock and final output tonnages (Danilov, 2003). The accumulation of millscale on the shopfloor over time usually create handling and disposal challenges.

Consequently, researchers have proposed various effecient methods and possible areas of its application (Seok-Heum, et al. 2010). For example, in the construction industry, the mixing of millscale in varying proportions has demonstrated increase in soil permeability, strength characteristics and decrease plasticity (Murthy, 2012). Another varitable area in which millscale has found application is in cement mortars (Saud Al-Otabi, 2008). The study reported impressive results on several mortar mixes of concrete made from millscale aggregates in terms of their compressive and flexural strengths including the drying shrinkage. The foregoings indicate high potentials for millscale usage in different engineering materials for enhanced performance. This is also capable of increasing the quantity recyclable thereby reducing drastically the environmental challenges pose by its accumulation on the shopfloor. This has been demonstrated in the recycling of aluminium swarf by direct incorporation in aluminium melts (Puga, et al. 2009). The current study investigates the quantity of iron particles weight percent addition in aluminium bronze that confers improved mechanical properties that makes the material suitable for applications requiring high strength combined with low wear rate.

1.2                                                           AIM OF THE STUDY

The mechanical properties of aluminum bronze depend primarily on aluminum content and other metals, including even copper and the brasses used for general purposes. The main aim of this work is to determine the mechanical properties of aluminium bronzes. The objective is to investigate how the addition of iron granules (millscale) can improve the mechanical properties of aluminum bronze.

1.3                                                         SCOPE OF THE STUDY

This study discussed on how aluminium bronzes give a mix of a chemo-mechanical properties that superseding many other alloy series that make them to be most preferred particularly for demanding applications. “Aluminium bronzes are most valued for their high strength and corrosion resistance in a wide range of aggressive media” [J. A. Wharton, R. C. Barik, G. Kear, R. J. K. Wood, K. R. Stokes and F. C. Walsh, 2005]. The copper component of the alloy prevents colonization of marine organisms including algae, lichens, barnacles and mussels, and therefore can be preferable to stainless steel or other non-cupric alloys in applications where such colonization would be unwanted.

1.4                                                   LIMITATION OF THE STUDY

As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-

1. Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.
2. Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).

• Time Constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work

1.5                                                         RESEARCH QUESTION

1. What are the properties of bronze?
2. What is aluminum bronze used for?

iii. What is the composition of Aluminium bronze?

1. What is added to Aluminium bronze to increase strength and hardness?

1.6                                             RESEARCH METHODOLOGY

In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.

1.7                                   PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.