Synthesis of nano al2o3 dispersion strengthened cu base composite materials by mechanochemical process
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY SCHOOL OF MATERIALS SCIENCE AND TECHNOLOGY THESIS OF GRADUATION Synthesis of nano Al 2 O 3 dispersion strengthened - Cu base composite materials by mechanochemical process Student: Phung Anh Tuan MSE-ATP-K52 Advisor: Dr. Nguyen Dang Thuy Hanoi, June 2012 1 Table of contents Preface 5 Chapter I: OVERVIEW 6 1.1 Composite materials 6 1.1.1 Definition 6 1.1.2 Class of composite materials 8 1.2 Metal matrix composites 9 1.2.1 Reinforcements 11 1.2.2 Matrix alloy systems 13 1.3 Partical-reinforced composites 14 1.3.1 Large-particle composites 14 1.3.2 Dispersion-strengthened composites 8 1.4 Bearing materials 19 1.4.1 Structure and properties and applications of bearing materials 20 1.4.2 Conventional bearing materials 22 1.5 Copper alumina composite 29 Chapter II: MECHANICAL ALLOYING 30 2.1 History 30 2.2 Milling 34 2.3 Mechanism of alloying 36 2.3.1. Ductile –Ductile components 38 2.3.2. Ductile – Brittle 39 2.3.3. Britle-Brittle component 40 Chapter III: EXPERIMENTAL PROCEDURE 41 3.1 Milling 41 3.2 Pressing 44 2 3.3 Sintering 45 Chapter IV: RESULTS AND DISCUSSION 48 4.1. Results after milling 48 4.2. Results after sintering 56 4.3. Porosity 58 4.4. Hardness 61 4.5. Microstructure 62 4.6. Experimental planning and process optimization 64 Chapter V: CONCLUSION AND SUGGESTION 71 5.1. Conclusions 71 5.2. Suggestions 71 References 72 3 List of figures No Titles Pages 1.1 Schematic representations of the various geometrical and spatial characteristics of particles of the dispersed phase that may influence the properties of composites. 8 1.2 A classification scheme for the various composite types discussed in this chapter. 9 1.3 Modulus of elasticity versus volume percent tungsten for a composite of tungsten particles dispersed within a copper matrix. Upper and lower bounds are according to Equations 16.1 and 16.2; experimental data points are included. 16 1.4 Photomicrograph of a WC–Co cemented carbide. Light areas are the cobalt matrix; dark regions, the particles of tungsten carbide. 17 1.5 Some bearings are made from copper alloys. 19 1.6 The popular designs for Engine bearing structure 25 2.1 Model 1-S attritor and arrangement of rotating arms on a shaft in the attrition ball mill. 35 2.2 Ball-powder-ball collision of powder mixture during mechanical alloying. 37 2.3 Scanning electron micrograph depicting the convoluted lamellar structure obtained during milling of a ductile- ductile component system (Ag-Cu). 39 2.4 Schematics of microstructure evolution during milling of a ductile-brittle combination of powders. This is typical of an oxide dispersion strengthened case 40 3.1 Milling chamber of the attritor. 42 3.2 The balls after milling process. 43 3.3 The synthesis process of materials. 44 3.4 Picture of compaction mold. 44 3.5 Picture of hydraulic pressing machine. 45 4 3.6 Sintering diagram of Cu-Al 2 O 3 46 3.7 Picture of Linn’s furnace for sintering. 46 4.1 SEM images form the initial sample mixture CuO-Cu-Al and after milling with speed 620rpm during 15h. 49 4.2 Powder Diffractometer Siemens D5005. 49 4.3 The X-ray diffraction diagram of original mixed powder material samples, including Cu, CuO and Al powder. 51 4.4 The results of X-ray analysis of powder samples after 4 hours milling. 52 4.5 The results of X-ray analysis of powder samples after 6 hours milling. 53 4.6 The results of X-ray analysis of powder samples after 12 hours milling. 54 4.7 The X-ray diffraction diagram of mixed powder material samples 55 4.8 The X-ray diffraction diagram of mixed powder material samples, after 12 hours milling and sintering. 57 4.9 Schematic of porosity measurement instrument 59 4.10 SEM images samples Cu- Al 2 O 3 (wt.10%) after sintering at 700°C in 3h (X30.000) 63 List of tables No Titles Pages 1.1 Properties of typical discontinuous reinforcements for aluminium and magnesium reinforcements. 12 2.1 Important milestones in the development of mechanical alloying. 33 4.1 Table of porosity of samples 60 4.2 Table of hardness of samples 61 4.3 Table of conditions of experiments 65 4.4 Table of factors 68 5 Preface As the time elapsed, living standard is continuously increased. One of the most important reasons for this is the developing in science and technology. The requirement for the new materials is much debated in our social. It set new challenges for the materials science and technology. In our country, there is a potential market in every fields of the industry. The materials nowadays need to have many unique properties. Moreover, the prices of synthesis have to be as low as possible. Thus, scientists tend to research to find the simplest method to create the best materials with a proper price. That’s a reason why I find interest in the mechanical alloying-the simple method to produce alloys with many advantages. Therefore, I have chosen the project namely “Synthesis of nano Al 2 O 3 dispersion strengthened - Cu base composite materials by mechanochemical process” In my project I will focus on composite base on Cu with Al 2 O 3 dispersion. Cu-Al 2 O 3 composite is one of the newest bearing materials of engines. This bearing system is developing in the world. However the synthesis method is keep in secret. I express my deep gratitude to Doctor Nguyen Dang Thuy who helped me to find enthusiasm in researching, showed me how to think critically and work effectively. He is not only my teacher but also my instructor in researching. I send my true thankfulness to every laboratory in School of Materials Science and Technology, Hanoi University of Science and Technology and all technicians, teachers, professors in School of Materials Science and Technology who have already helped me to complete this project. And, thanks to other lovely members in my research group, who have worked with me and helped me a lot. 6 Chapter I: OVERVIEW 1.1. COMPOSITE MATERIALS 1.1.1 Definition Many of our modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. This is especially true for materials that are needed for aerospace, underwater, and transportation applications. For example, aircraft engineers are increasingly searching for structural materials that have low densities, are strong, stiff, and abrasion and impact resistant, and are not easily corroded.This is a rather formidable combination of characteristics. Frequently, strong materials are relatively dense; also, increasing the strength or stiffness generally results in a decrease in impact strength. Material property combinations and ranges have been, and are yet being, extended by the development of composite materials. Generally speaking, a composite is considered to be any multiphase material that exhibits a significant proportion of the properties of both constituent phases such that a better combination of properties is realized. According to this principle of combined action, better property combinations are fashioned by the judicious combination of two or more distinct materials. Property trade-offs are also made for many composites. Composites of sorts have already been discussed; these include multiphase metal alloys, ceramics, and polymers. For example, pearlitic steels have a microstructure consisting of alternating layers of ferrite and cementite. The ferrite phase is soft and ductile, whereas cementite is hard and very brittle. The combined mechanical characteristics of the pearlite (reasonably high ductility and strength) 7 are superior to those of either of the constituent phases. There are also a number of composites that occur in nature. For example, wood consists of strong and flexible cellulose fibers surrounded and held together by a stiffer material called lignin. Also, bone is a composite of the strong yet soft protein collagen and the hard, brittle mineral apatite. A composite, in the present context, is a multiphase material that is artificially made, as opposed to one that occurs or forms naturally. In addition, the constituent phases must be chemically dissimilar and separated by a distinct interface. Thus, most metallic alloys and many ceramics do not fit this definition because their multiple phases are formed as a consequence of natural phenomena. In designing composite materials, scientists and engineers have ingeniously combined various metals, ceramics, and polymers to produce a new generation of extraordinary materials. Most composites have been created to improve combinations of mechanical characteristics such as stiffness, toughness, and ambient and high-temperature strength. Many composite materials are composed of just two phases; one is termed the matrix, which is continuous and surrounds the other phase, often called the dispersed phase. The properties of composites are a function of the properties of the constituent phases, their relative amounts, and the geometry of the dispersed phase. “Dispersed phase geometry” in this context means the shape of the particles and the particle size, distribution, and orientation; these characteristics are represented in Figure 1.1 8 Figure 1.1 Schematic representations of the various geometrical and spatial characteristics of particles of the dispersed phase that may influence the properties of composites: (a) concentration, (b) size, (c) shape, (d) distribution, and (e) orientation. (From Richard A. Flinn and Paul K. Trojan, Engineering Materials and Their Applications, 4th edition. Copyright © 1990 by John Wiley & Sons, Inc. Adapted by permission of John Wiley & Sons, Inc.) 1.1.2 Class of composite materials One simple scheme for the classification of composite materials is shown in Figure 1.2, which consists of three main divisions: particle-reinforced, fiber- reinforced, and structural composites; also, at least two subdivisions exist for each. The dispersed phase for particle-reinforced composites is equiaxed (i.e., particle dimensions are approximately the same in all directions); for fiber-reinforced composites, the dispersed phase has the geometry of a fiber (i.e., a large length-to- diameter ratio). Structural composites are combinations of composites and 9 homogeneous materials. The discussion of the remainder of this chapter will be organized according to this classification scheme. Figure 1.2 A classification scheme for the various composite types discussed in this chapter. 1.2 METAL MATRIX COMPOSITES As the name implies, for metal-matrix composites (MMCs) the matrix is a ductile metal. These materials may be utilized at higher service temperatures than their base metal counterparts; furthermore, the reinforcement may improve specificstiffness, specific strength, abrasion resistance, creep resistance, thermal conductivity, and dimensional stability. Some of the advantages of these materials over the polymer-matrix composites include higher operating temperatures, nonflammability, and greater resistance to degradation by organic fluids. Metal- matrix composites are much more expensive than PMCs, and, therefore, their (MMC) use is somewhat restricted. The superalloys, as well as alloys of aluminum, magnesium, titanium, and copper, are employed as matrix materials. The reinforcement may be in the form of particulates, both continuous and discontinuous fibers, and whiskers; concentrations normally range between 10 and 60 vol%. Continuous fiber [...]... electrical conductivity of Cu -Al2O3 composite was the object of this paper 29 Chapter II: MECHANICAL ALLOYING There are many methods to synthesis Cu -Al2O3 such as melting, powder metallurgy and mechanical alloying However, mechanical alloying has some advantages By choosing the pure metal as sources of the synthesis Cu -Al2O3, with the room temperature therefore, the vaporizing metal does not occur The chemical... nonmetallic bearing materials are hard to be applied for engineering parts 1.5 COPPER ALUMINA COMPOSITE Dispersion strengthened Cu - Al2O3 composite materials are extensively used as materials for products which require high-strength and electrical properties, such as electrode materials for lead wires, relay blades, contact supports and bearing materials for industry Electrode tips made of this composite material... of units in large item numbers is possible The relatively high isotropy of the properties in comparison to the long-fiber continuous reinforced light metals and the possibility of processing of composites by forming and cutting production engineering are further advantages 12 1.2.2 Matrix Alloy Systems The selection of suitable matrix alloys is mainly determined by the intended application of the composite. .. other materials (e.g., silica) is much less effective because this special interaction between the rubber molecules and particle surfaces does not exist Figure 1.4 is an electron micrograph of a carbon black-reinforced rubber 1.3.2 Dispersion- strengthened composites Metals and metal alloys may be strengthened and hardened by the uniform dispersion of several volume percent of fine particles of a very... in the development of the field are presented in table: Time Milestones 1966 Development of ODS nickel -base alloys 1981 Amorphization of intermetallics 1982 Disordering of ordered compounds 1983 Amorphization of blended elemental powder mixtures 1987/88 Synthesis of nanocrystalline phases 1989 Occurrence of displacement reactions Table 2.1 Important milestones in the development of mechanical alloying... the development of the present process In the early 1960s, INCO had developed a process for manufacturing graphitic aluminum alloys by injecting nickel-coated graphite particles into a molten aluminum bath by argon sparging A modification of the same technique was tried to inoculate nickel-based alloys with a dispersion of nickel-coated, fine refractory oxide particles The purpose of nickel coating... produce pure metals, nano- composites, and a variety of commercially useful materials Efforts were also under way since the early 1990s to understand the process fundamentals of MA through modeling studies Because of all these special attributes, this simple, but effective, processing technique has been applied to metals, ceramics, polymers, and composite materials The attributes of mechanical alloying... withstand the high temperatures generated by the cutting action on materials that are extremely hard No single material could possibly provide the combination of properties possessed by a cermet Relatively large volume fractions of the particulate phase may be utilized, often exceeding 90 vol%; thus the abrasive action of the composite is maximized A photomicrograph of a WC Co cemented carbide is shown... powders are characterized by very fine, nano- scaled grain structure, which may be retained even during compaction This fine-grained structure contributes to copper matrix strengthening together with Al2O3 particles In this study the copper matrix was strengthened by Al2O3 particles by internal oxidation and mechanical alloying The effect of the various size of copper and Al2O3 powder particles on structure,... the atomic or molecular level; rather, continuum mechanics is used For most of these composites, the particulate phase is harder and stiffer than the matrix These reinforcing particles tend to restrain movement of the matrix phase in the vicinity of each particle In essence, the matrix transfers some of the applied stress to the particles, which bear a fraction of the load The degree of reinforcement . namely Synthesis of nano Al 2 O 3 dispersion strengthened - Cu base composite materials by mechanochemical process In my project I will focus on composite base on Cu with Al 2 O 3 dispersion. . UNIVERSITY OF SCIENCE AND TECHNOLOGY SCHOOL OF MATERIALS SCIENCE AND TECHNOLOGY THESIS OF GRADUATION Synthesis of nano Al 2 O 3 dispersion strengthened - Cu base composite materials. rubber. 1.3.2 Dispersion- strengthened composites Metals and metal alloys may be strengthened and hardened by the uniform dispersion of several volume percent of fine particles of a very hard