Alloys
Alloys are solid solutions composed of two or more metals, or a metal and a non-metal, that are mixed together at the atomic level. This results in a material with properties distinct from those of its individual components. Alloys are commonly used in various industries due to their enhanced strength, durability, and resistance to corrosion compared to pure metals.
5 Key excerpts on "Alloys"
eBook - ePubApplied Welding Engineering
Processes, Codes, and Standards
- Ramesh Singh(Author)
- 2011(Publication Date)
- Butterworth-Heinemann(Publisher)
...Chapter 2. Alloys Chapter Outline Alloys 7 Effects of Alloying Elements 8 Carbon Steels 8 Sulfur 8 Manganese 8 Phosphorus 9 Silicon 9 Alloy Steels 9 The Effect of Alloying Elements on Ferrite 9 Effects of Alloying Elements on Carbide 10 Nickel Steels (2xx Series) 10 Nickel-Chromium Steels (3xx Series) 10 Manganese Steels (31x Series) 10 Molybdenum Steels (4xx Series) 11 Chromium Steels (5xx Series) 11 An alloy is a substance that has metallic properties and is composed of two or more chemical elements, of which the primary one is a metal. The added elements create intermetallic or interstitial compounds. Metals are generally alloyed with the aim of improving a property or a specific set of properties. A number of elements are added to steel, including sulfur, manganese, phosphorous, silicon, nickel, aluminum, silicon, copper, and cobalt. These elements affect the phase transitions and crystal structure of the steel and so change its mechanical properties. Keywords alloy, metal, steel, mechanical property, phase transition Alloys An alloy is a substance that has metallic properties and is composed of two or more chemical elements, of which at least one, the primary one, is a metal. A binary alloy system is a group of Alloys that can be formed by two elements combined in all possible proportions. Homogeneous Alloys consist of a single phase and mixtures consist of several phases. A phase is anything that is homogeneous and physically distinct if viewed under a microscope. When an allotropic metal undergoes a change in crystal structure, it undergoes a phase change. There are three possible phases in the solid state: • Pure metal • Intermediate alloy phase or compound • Solid solution. Compounds have their own characteristic physical, mechanical, and chemical properties and exhibit definite melting and freezing points...
eBook - ePub- W. Bolton, R.A. Higgins(Authors)
- 2014(Publication Date)
- Routledge(Publisher)
...If present in an alloy in large amounts, an intermetallic compound will often form brittle intercrystalline networks. The strength and toughness of such an alloy would be negligible. 8.5 Summary: Alloys In a study of metallurgy, the term phase refers to any chemically stable, single homogeneous constituent in an alloy. Thus, in a solid alloy, a phase may be a solid solution, an intermetallic compound or, of course, a pure metal. A homogeneous liquid solution from which an alloy is solidifying also constitutes a phase. Any of the solid phases form the basic units of which metallic Alloys are composed. It may be helpful therefore to summarise their properties: Solid solutions are formed when one metal is very similar to another, both physically and chemically, and is able to replace it, atom for atom, in a crystal structure or if the atoms of the second element are very small and able to fit into the spaces between the larger atoms of the other metal. Solid solutions are stronger than pure metals, because the presence of atoms of the second metal causes some distortion of the crystal structure, thus making slip more difficult. At the same time, solid solutions retain much of the toughness and ductility of the original pure metal. Intermetallic compounds are formed by chemical combination, and the resultant substance generally bears little resemblance to its parent metals. Most intermetallic compounds are hard and brittle, and of limited use in engineering Alloys. Eutectics are formed when two metals, soluble in each other in the liquid state, become insoluble in each other in the solid state. Then, alternate layers or bands of each metal form, until the alloy is completely solid. This occurs at a fixed temperature, which is below the melting-point of either of the two pure metals. When two metals are only partially soluble in each other in the solid state, a eutectic may form consisting of alternate layers of two solid solutions...
eBook - ePub- Sankara Papavinasam(Author)
- 2013(Publication Date)
- Gulf Professional Publishing(Publisher)
...The atoms are not in their proper places in grain boundaries because the periodic nature of the grain formation has been disrupted. Because of this different orientation of the atomic structures, the properties of grain boundaries are different from those of grains. The study of the structure of metals, i.e., the study of grains and grain boundaries by optical microscopy is called metallography. Standards providing guidelines on terminology related to metallography include: • ASTM E7, ‘Terminology Relating to Metallography’ In general, as the number of grain boundaries increases (consequently as the grain size decreases) the mechanical properties (strength, ductility, and toughness) improve, but chemical and corrosion resistance decrease. Grain boundaries have higher energy than the grains, hence are preferentially attacked by chemicals. Most pure metals do not possess the properties (mechanical strength, chemical resistance, and corrosion resistance) necessary for engineering applications. Therefore other elements are introduced into the metal to provide these. A combination of two or more elements in which at least one of the elements is a metal is called an alloy or solid solution. In an alloy, the parent metal is the solvent and the alloying element is the solute. If the solute element is small (e.g., carbon, nitrogen, or hydrogen) the energetically favorable situation is one in which the solute element occupies the interstitial positions; i.e., the alloying elements occupy the interstitial holes between the parent metal atoms (Figure 3.4 (A)). 4 The resulting alloy is known as interstitial solid solution. If the solute element is large (e.g., chromium, nickel, or manganese) then it will substitute the atom of the parent metal...
eBook - ePub- R. Winston Revie, R. Winston Revie(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
...Chapter 42 Metastable Alloys K. Hashimoto Tohoku Institute of Technology, Sendai, Japan A. Structural Characteristics Amorphous Alloys consist of at least two components and have no long-range atomic order. They are produced by a variety of methods based on rapid solidification of the alloy constituents from the gas, liquid, and aqueous phases. Mechanical alloying, that is, solid-state mixing, is also effective for preparation of amorphous alloy powders. Vitrification of metal surfaces is also made by destruction of the long-range atomic order in the surfaces of solid metals. The formation of the structure with no long-range atomic order is based on the prevention of solid-state diffusion during solidification, and hence the Alloys are free of compositional fluctuations formed by solid-state diffusion, such as second phases, precipitates, and segregates. The amorphous Alloys are therefore regarded as ideal, chemically homogeneous Alloys composed of thermodynamically metastable single-phase solid solutions supersaturated with alloy constituents. This characteristic is particularly suitable in producing new Alloys possessing specific properties. Even if amorphous single-phase Alloys are not formed, Alloys prepared by amorphization methods are often composed of nanocrystalline phases supersaturated with alloying elements. From a corrosion point of view they can be considered as homogeneous Alloys. B. Corrosion-Resistant Alloys in Aqueous Solutions The corrosion behavior of amorphous Alloys has received particular attention since the extraordinarily high corrosion resistance of amorphous Fe–Cr–metalloid Alloys was reported in 1974 [1]...
eBook - ePubHandbook of Non-Ferrous Metal Powders
Technologies and Applications
- Oleg D Neikov, N. A. Yefimov, Stanislav Naboychenko, Irina B Mourachova, Victor G Gopienko, Irina V Frishberg, Dina V Lotsko, Stanislav Naboychenko, Oleg D Neikov, Irina B Mourachova, Victor G Gopienko, Irina V Frishberg, Dina V Lotsko(Authors)
- 2009(Publication Date)
- Elsevier Science(Publisher)
...Chapter 13 Advanced Aluminum Alloy Powders Oleg D. Neikov Frantsevich Institute for Problems of Materials Science (IPMS), Kiev, Ukraine Emerging processes, such as rapid solidification, mechanical alloying and spray forming, create powders that upon subsequent consolidation provide significant improvements in room and elevated temperature strength, fracture toughness, fatigue life and corrosion resistance. The real advantage of powder metallurgy processing is in the production of new Alloys and composites with metallurgical structures and compositions that cannot be produced by ingot metallurgy. Rapid solidification extends the solubility of alloying elements, particularly transition and rare earth elements, and refines the structure of inter-metallic phases responsible for improved mechanical properties. Mechanical alloying (MA) is a dry, high-energy milling process producing dispersions of insoluble oxides and carbides that stabilize the microstructure leading to high strength at elevated temperatures in the consolidated materials. By blending the alloy powder with a strengthening phase, discontinuously reinforced aluminum–matrix composites containing insoluble dispersoids (oxides and carbides), particulates, whiskers or fibers are produced for high-performance structural applications [ 1 – 5 ]. Table 13.1 contains the chemical composition commercially available of aluminum PM Alloys and dispersion-strengthened composites. Table 13.1 Nominal chemical composition of aluminum PM Alloys and dispersion strengthened composites The discontinuously reinforced aluminum–matrix composites are generally isotropic and less costly in comparison with continuous-fiber-reinforced aluminum–matrix composites. Silicon carbide or alumina-particle-reinforced aluminum composites have higher stiffness and, principally, high wear resistance in comparison with the unreinforced aluminum Alloys...
