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Aluminum alloys 
Table of Contents 
1 Aluminum Alloys: ......................................................................
Aluminum alloys 
6.1 Classifications of Cast Aluminum Alloys ................................................................
Aluminum alloys 
1 Aluminum Alloys: 
Aluminum the most second plentiful metallic element on earth became an economic compe...
Aluminum alloys 
 7xx.x series zinc 
 8xx.x series tin 
 9xx.x other elements 
4 Heat treatment of cast aluminum alloys...
Aluminum alloys 
alloys include some of the highest strength heat treatable aluminum alloys. The most common 
applications...
Aluminum alloys 
5.1.1 Commercial alloys of 2xxx series 
The three most widely used wrought aluminum-copper alloys are 201...
Aluminum alloys 
Figure 2: Al-Mn phase diagram 
These are moderate strength non-heat treatable materials that retain stren...
Aluminum alloys 
Figure 3: Al-Si phase diagram 
The aluminum-rich portion of the aluminum silicon alloy system is shown. T...
Aluminum alloys 
Figure 4: Al-Mg phase diagram 
5.4.1 Commercial Al-Mg alloys 
The wrought alloys are characterized by goo...
Aluminum alloys 
Figure 5: Al-Mg2Si phase diagram with aluminum rich portion 
The 5xxx series alloy used in the form of pl...
Aluminum alloys 
Figure 6: Al-Zn phase diagram with aluminum rich portion 
Commercial wrought alloys contain zinc, magnesi...
Aluminum alloys 
5.7.4 Titanium (Ti) 
Titanium is added to aluminum primarily as a grain refiner. The grain refining effec...
Aluminum alloys 
similarly classified into non-heat-treatable and heat-treatable types. The major difference is that the 
...
Aluminum alloys 
modifications, as previously mentioned, are identified by a capital letter preceding the numerical 
desig...
Aluminum alloys 
7.3.1 Example Al-Si cast alloy 
Aluminum-silicon casting alloys have excellent castability and resistance...
Aluminum alloys 
7.6 Aluminum-Tin alloy 8xx.x 
Aluminum-tin alloys that contain about 6% Sn (and small amounts of copper a...
Aluminum alloys 
 383 & 384: 
These alloys are a modification of 380. Both provide better die filling, but with a moderat...
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Aluminum alloys cast and wrought

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Aluminum alloys cast and wrought

  1. 1. Aluminum alloys Table of Contents 1 Aluminum Alloys: .......................................................................................................................... 3 2 Types of aluminum alloys .............................................................................................................. 3 3 Cast aluminum Alloys: ................................................................................................................... 3 4 Heat treatment of cast aluminum alloys ......................................................................................... 4 4.1 Heat treatable alloy.................................................................................................................. 4 4.2 Non heat treatable cast alloys .................................................................................................. 4 5 Effect of Alloying Elements: .......................................................................................................... 4 5.1 Copper (Cu) 2xxx: ................................................................................................................... 4 5.1.1 Commercial alloys of 2xxx series .................................................................................... 6 5.2 Manganese (Mn) 3xxx ............................................................................................................ 6 5.2.1 Commercial alloys of 3xxx .............................................................................................. 7 5.3 Silicon (Si) 4xxx...................................................................................................................... 7 5.4 Magnesium (Mg) 5xxx ............................................................................................................ 8 5.4.1 Commercial Al-Mg alloys ............................................................................................... 9 5.5 Magnesium and Silicon (Mg2Si) 6xxx .................................................................................... 9 5.5.1 Magnox Commercial alloys of 6xxx.............................................................................. 10 5.6 Zinc (Zn) 7xxx ...................................................................................................................... 10 5.7 Others elements 8xxx ............................................................................................................ 11 5.7.1 Iron (Fe) ......................................................................................................................... 11 5.7.2 Chromium (Cr)............................................................................................................... 11 5.7.3 Nickel (Ni) ..................................................................................................................... 11 5.7.4 Titanium (Ti) .................................................................................................................. 12 5.7.5 Zirconium (Zr) ............................................................................................................... 12 5.7.6 Lithium (Li) ................................................................................................................... 12 5.7.7 Lead (Pb) and Bismuth (Bi) ........................................................................................... 12 6 Cast Aluminum Alloys ................................................................................................................ 12 Foundry Engineering Page 1
  2. 2. Aluminum alloys 6.1 Classifications of Cast Aluminum Alloys ............................................................................. 13 7 Effect of alloying addition ........................................................................................................... 14 7.1 Aluminum-copper alloys 2xx.x: ............................................................................................ 14 7.1.1 Commercial Al-Cu cast alloy......................................................................................... 14 7.2 Aluminum-Silicon alloy with copper and magnesium 3xx.x ................................................ 14 7.3 Binary aluminum-silicon alloys 4xx.x .................................................................................. 14 7.3.1 Example Al-Si cast alloy ............................................................................................... 15 7.4 Aluminum-Magnesium alloy 5xx.x ...................................................................................... 15 7.4.1 Commercial Al-Mg cast alloy ........................................................................................ 15 7.5 Aluminum-Zinc alloy 7xx.x .................................................................................................. 15 7.5.1 Commercial Al-Zn alloy ................................................................................................ 15 7.6 Aluminum-Tin alloy 8xx.x .................................................................................................... 16 7.6.1 Commercial Al-Ti alloy ................................................................................................. 16 8 Some common casting alloys and their properties: ..................................................................... 16 Foundry Engineering Page 2
  3. 3. Aluminum alloys 1 Aluminum Alloys: Aluminum the most second plentiful metallic element on earth became an economic competitor in engineering applications as recently as the end of the 19th century. It was to become a metal for its time. For the most important industrial development would, by demanding material characteristic consistent with the unique qualities of aluminum and its alloys. Greatly benefits growth in the production and use of new metal. 2 Types of aluminum alloys Aluminum alloys are alloys in which aluminum (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications. Namely 1. casting alloys 2. wrought alloys Both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminum is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminum alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminum alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics. Aluminum alloys are widely used in engineering structures and components where light weight or corrosion resistance is required. 3 Cast aluminum Alloys: The Aluminum Association (AA) has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminum, e.g. 150.x corresponds to a minimum of 99.50% aluminum. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively.[1] The main alloying elements in the AA system are as follows.  1xx.x series are minimum 99% aluminum  2xx.x series copper  3xx.x series silicon, copper and/or magnesium  4xx.x series silicon  5xx.x series magnesium Foundry Engineering Page 3
  4. 4. Aluminum alloys  7xx.x series zinc  8xx.x series tin  9xx.x other elements 4 Heat treatment of cast aluminum alloys When the term is applied to aluminum alloys, however, its use frequently is restricted to the specific operations employed to increase strength and hardness of the precipitation hardenable wrought and cast alloys.  Heat treatable alloy  Non heat treatable alloy 4.1 Heat treatable alloy Aluminum alloy of this type belongs to system with limited solubility in solid solution. These are precipitated hardenable alloy. The main character of this type of alloy system is a temperature dependent equilibrium solid solubility, which increase with increase in temperatue.in addition other requirements are retaining single phase supersaturated solution by quenching and coherent state. Examples of this group is  2xxx Al-Cu alloy and Al-Cu-Mg alloy.  6xxx series include Al-Zn, Al-Zn-Mg alloy  7xxx series include Al-Zn, Al-Zn-Mg-Cu type alloys 4.2 Non heat treatable cast alloys These alloys do not respond to heat treatment because these alloys consist of homogeneous solid solution with or without non-coherent precipitate and show low strength and high ductility.  Pure aluminum (1100), Al-Mn (3003)  5xxx Al-Mg alloys  6xxx Al-Si alloys 5 Effect of Alloying Elements: 5.1 Copper (Cu) 2xxx: The aluminum-copper alloys typically contain between 2 to 10% copper, with smaller additions of other elements. The copper provides substantial increases in strength and facilitates precipitation hardening. The introduction of copper to aluminum can also reduce ductility aönd corrosion resistance. The susceptibility to solidification cracking of aluminum-copper alloys is increased; consequently, some of these alloys can be the most challenging aluminum alloys to weld. These Foundry Engineering Page 4
  5. 5. Aluminum alloys alloys include some of the highest strength heat treatable aluminum alloys. The most common applications for the 2xxx series alloys are aerospace, military vehicles and rocket fins. The maximum solubility of copper in aluminum is 5.56% at 1018oF. Figure 1: Al-Cu phase diagram k This is full phase diagram of aluminum and copper but useful portion is only up to 10% of copper. From 2-5.56% of copper is mostly used for heat treatment purposes. The theta (θ) phase is an intermediate alloy phase whose com-position corresponds closely to the compound CuAl2. These alloys may contain smaller amounts of silicon, iron, magnesium, manganese, chromium, and zinc. Table 1 phases present in Al-Cu phase diagram of heat treatable portion Foundry Engineering Page 5
  6. 6. Aluminum alloys 5.1.1 Commercial alloys of 2xxx series The three most widely used wrought aluminum-copper alloys are 2014, 2017, and 2024. 5.1.1.1 Duralumin 2017 Al-Cu alloy The oldest of all the heat treatable aluminum alloys is duralumin (2017) containing 4 percent copper. This alloy is widely used for rivets in aircraft construction. Since this is a natural-aging alloy, after solution treatment it is refrigerated to prevent aging. As a single phase, in the Solution treated condition, it has good ductility so that the rivet head may be easily formed. Subsequent return of the material to room temperature causes precipitation of the θ phase as small submicroscopic particles, increasing the hardness and strength. 5.1.1.2 2014 Al-Cu alloy Alloy 2014 has higher copper and manganese content than 2017 and is susceptible to artificial aging. In the artificially aged temper, 2014 has a higher tensile strength, much higher yield strength, and lower elongation than 2017. This alloy is used for heavy-duty forgings, aircraft fittings, and truck frames. 5.1.1.3 2024 Al-Cu alloy Alloy 2024, containing 4.5 percent copper and 1.5 percent magnesium, develops the highest strengths of any naturally aged aluminum-copper type of alloy. The higher magnesium content, compared with 2017, makes it more difficult to fabricate. A combination of strain hardening and aging will develop the maximum yield strength attainable in high-strength alloy sheet. Typical uses of 2024 alloy are aircraft structures, rivets, hardware, truck wheels and screw-machine products 5.2 Manganese (Mn) 3xxx The addition of manganese to aluminum increases strength somewhat through solution strengthening and improves strain hardening while not appreciably reducing ductility or corrosion resistance. Foundry Engineering Page 6
  7. 7. Aluminum alloys Figure 2: Al-Mn phase diagram These are moderate strength non-heat treatable materials that retain strength at elevated temperatures and are seldom used for major structural applications. The most common applications for the 3xxx series alloys are cooking utensils, radiators, air conditioning condensers, evaporators, heat exchangers and associated piping systems. . The maximum solubility of manganese in the solid solution is 1.82 at the eutectic temperature of 12160F. Because of the limited solubility, manganese is not used as a major alloying element in any casting alloys and is used in only a few wrought alloys. 5.2.1 Commercial alloys of 3xxx One of the alloys in this group is the popular 3003 alloy, which has good formability, very good resistance to corrosion, and good weldability. Typical applications are utensils, food and chemical handling and storage equipment, gasoline and oil tank, pressure vessels and piping. 5.3 Silicon (Si) 4xxx The addition of silicon to aluminum reduces melting temperature and improves fluidity. Silicon alone in aluminum produces a non-heat treatable alloy; however, in combination with magnesium it produces a precipitation hardening heat-treatable alloy. Consequently, there are both heat-treatable and non-heat treatable alloys within the 4xxx series. Silicon additions to aluminum are commonly used for the manufacturing of castings. The most common applications for the 4xxx series alloys are filler wires for fusion welding and brazing of aluminum. Foundry Engineering Page 7
  8. 8. Aluminum alloys Figure 3: Al-Si phase diagram The aluminum-rich portion of the aluminum silicon alloy system is shown. The maximum solubility of silicon in α solid solution is 1.65 percent at the eutectic temperature of 1071oF. Although the solvus line shows lower solubility at lower temperatures, these alloys are generally not heat treatable. 5.4 Magnesium (Mg) 5xxx The addition of magnesium to aluminum increases strength through solid solution strengthening and improves their strain hardening ability. These alloys are the highest strength non heat treatable aluminum alloys and are, therefore, used extensively for structural applications. The 5xxx series alloys are produced mainly as sheet and plate and only occasionally as extrusions. The reason for this is that these alloys strain harden quickly and, are, therefore difficult and expensive to extrude. Although the solvus line, show considerable decrease in solubility with decrease in temperature of magnesium in aluminum. Some common applications for the 5xxx series alloys are truck and train bodies, buildings, armored vehicles, ship and boat building, chemical tankers, pressure vessels and cryogenic tanks. Foundry Engineering Page 8
  9. 9. Aluminum alloys Figure 4: Al-Mg phase diagram 5.4.1 Commercial Al-Mg alloys The wrought alloys are characterized by good weldability, good corrosion resistance, and moderate strength.  Alloy 5005 (0.8 percent magnesium) is used for architectural extrusions  alloy 5050 (1.2 percent magnesium) for tubing and automotive gas and oil lines  alloy 5083 (4.5 percent magnesium) for marine and welded structural applications; and alloy 5056  (5.2 percent magnesium) for insect screens, cable sheathing, and rivets for use with magnesium alloys. 5.5 Magnesium and Silicon (Mg2Si) 6xxx The addition of magnesium and silicon to aluminum produces the compound magnesium-silicide (Mg2Si). The formation of this compound provides the 6xxx series their heat-treatability. The 6xxx series alloys are easily and economically extruded and for this reason are most often found in an extensive selection of extruded shapes. These alloys form an important complementary system with the 5xxx series alloy. Foundry Engineering Page 9
  10. 10. Aluminum alloys Figure 5: Al-Mg2Si phase diagram with aluminum rich portion The 5xxx series alloy used in the form of plate and the 6xxx are often joined to the plate in some extruded form. Some of the common applications for the 6xxx series alloys are handrails, drive shafts, automotive frame sections, bicycle frames, tubular lawn furniture, scaffolding, stiffeners and braces used on trucks, boats and many other structural fabrications. 5.5.1 Magnox Commercial alloys of 6xxx The wrought alloys include 6053, 6061, and 6063 are mostly used. 5.5.1.1 6061 Al-Mg2Si  Construction of aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft than commercial or military aircraft.  Construction, including small utility boats.  Automotive parts, such as wheel spacers.  Aluminum cans for the packaging of foodstuffs and beverages. 5.5.1.2 6053 Al-Mg2Si  Aluminum 6053 alloy is chiefly used in the manufacture of rod and wire for rivets. It is also used in several cold heading applications, where it is used in the form of T-temper wire. 5.6 Zinc (Zn) 7xxx The addition of zinc to aluminum (in conjunction with some other elements, primarily magnesium and/or copper) produces heat-treatable aluminum alloys of the highest strength. The solubility of zinc in aluminum is 31.6 percent at 527oF, decreasing to 5.6 percent at 257oF. Foundry Engineering Page 10
  11. 11. Aluminum alloys Figure 6: Al-Zn phase diagram with aluminum rich portion Commercial wrought alloys contain zinc, magnesium, and copper with smaller additions of manganese and chromium. The zinc substantially increases strength and permits precipitation hardening. Some of these alloys can be susceptible to stress corrosion cracking and for this reason are not usually fusion welded. Other alloys within this series are often fusion welded with excellent results. Some of the common applications of the 7xxx series alloys are aerospace, armored vehicles, baseball bats and bicycle frames. 5.7 Others elements 8xxx This series include elements which are rarely used in aluminum alloys. Some of these are impurity atoms 5.7.1 Iron (Fe) Iron is the most common impurity found in aluminum and is intentionally added to some pure (1xxx series) alloys to provide a slight increase in strength. 5.7.2 Chromium (Cr) Chromium is added to aluminum to control grain structure, to prevent grain growth in aluminum-magnesium alloys, and to prevent recrystallization in aluminum-magnesium-silicon or aluminum-magnesium- zinc alloys during heat treatment. Chromium will also reduce stress corrosion susceptibility and improves toughness. 5.7.3 Nickel (Ni) Nickel is added to aluminum-copper and to aluminum-silicon alloys to improve hardness and strength at elevated temperatures and to reduce the coefficient of expansion. Foundry Engineering Page 11
  12. 12. Aluminum alloys 5.7.4 Titanium (Ti) Titanium is added to aluminum primarily as a grain refiner. The grain refining effect of titanium is enhanced if boron is present in the melt or if it is added as a master alloy containing boron largely combined as TiB2. Titanium is a common addition to aluminum weld filler wire as it refines the weld structure and helps to prevent weld cracking. 5.7.5 Zirconium (Zr) Zirconium is added to aluminum to form a fine precipitate of intermetallic particles that inhibit recrystallization. 5.7.6 Lithium (Li) The addition of lithium to aluminum can substantially increase strength and, Young’s modulus, provide precipitation hardening and decreases density. 5.7.7 Lead (Pb) and Bismuth (Bi) Lead and bismuth are added to aluminum to assist in chip formation and improve machinability. These free machining alloys are often not weldable because the lead and bismuth produce low melting constituents and can produce poor mechanical properties and/or high crack sensitivity on solidification.  Summary:  There are many aluminum alloys used in industry today - over 400 wrought alloys and over 200 casting allloys are currently registered with the Aluminum Association. Certainly one of the most important considerations encountered during the welding of aluminum is the identification of the aluminum base alloy type to be welded. If the base material type of the component to be welded is not available through a reliable source, it can be difficult to select a suitable welding procedure. There are some general guidelines as to the most probable type of aluminum used in different applications, such as those mentioned above. However, it is very important to be aware that incorrect assumptions as to the chemistry of an aluminum alloy can result in very serious effects on the weld performance. It is strongly recommended that positive identification of the type of aluminum is made and that welding procedures be developed and tested in order to verify weld performance. 6 Cast Aluminum Alloys Aluminum casting alloys are the most versatile of all common foundry alloys and generally have the highest castability ratings. Aluminum casting alloys are based on the same alloy systems as those of wrought aluminum alloys, are strengthened by the same mechanisms (with the exception of strain hardening), and are Foundry Engineering Page 12
  13. 13. Aluminum alloys similarly classified into non-heat-treatable and heat-treatable types. The major difference is that the casting alloys used in the greatest volumes contains alloying additions of silicon far in excess of that found (or used) in most wrought alloys. Aluminum casting alloys must contain, in addition to strengthening elements, sufficient amounts of eutectic forming elements (usually silicon) in order to have adequate fluidity to feed the shrinkage that occurs in all but the simplest castings. 6.1 Classifications of Cast Aluminum Alloys They are classified as under.  1xx.x: Controlled unalloyed compositions  2xx.x: Aluminum alloys containing copper as the major alloying element  3xx.x: Aluminum-silicon alloys are also containing magnesium and/or copper  4xx.x: Binary aluminum-silicon alloys  5xx.x: Aluminum alloys containing magnesium as the major alloying element  6xx.x: Currently unused  7xx.x: Aluminum alloys containing zinc as the major alloying element, usually also containing additions of either copper, magnesium, chromium, manganese, or combinations of these elements  8xx.x: Aluminum alloys containing tin as the major alloying element  9xx.x: Currently unused Designations in the form xxx.1 and xxx.2 include the composition of specific alloys in remelt ingot form suitable for foundry use. Designations in the form xxx.0 in all cases define composition limits applicable to castings. Further variations in specified compositions are denoted by prefix letters used primarily to define differences in impurity limits. Accordingly, one of the most common gravity cast alloys, 356, has variations A356, B356, and C356; each of these alloys has identical major alloy contents but has decreasing specification limits applicable to impurities, especially iron content. In designations of the 1xx.x type, the second and third digits indicate minimum aluminum content (99.00% or greater); these digits are the same as the two to the right of the decimal point in the minimum aluminum percentage expressed to the nearest 0.01%. The fourth digit in 1xx.x designations, which is to the right of the decimal point, indicates product form: 0 denotes castings (such as electric motor rotors), and 1 denotes ingot. In 2xx.x through 8xx.x designations for aluminum alloys, the second and third digits have no numerical significance but only identify the various alloys in the group. The digit to the right of the decimal point indicates product form: 0 denotes castings, 1 denotes standard ingot, and 2 denotes ingot having composition ranges narrower than but within those of standard ingot. Alloy Foundry Engineering Page 13
  14. 14. Aluminum alloys modifications, as previously mentioned, are identified by a capital letter preceding the numerical designation. 7 Effect of alloying addition 7.1 Aluminum-copper alloys 2xx.x: Aluminum-copper alloys that contain 4 to 5% Cu, with the usual impurities iron and silicon and sometimes with small amounts of magnesium, are heat treatable and can reach quite high strengths and ductility, especially if prepared from ingot containing less than 0.15% Fe. The aluminum-copper alloys are single-phase alloys. Unlike the silicon alloys, there is no highly fluid second phase available at the late stages of solidification. When available, a second phase will aid the required feeding of shrinkage areas and will help compensate for solidification stresses. It is the alloy of aluminum and copper. And it is capable of developing highest strengths among all casting alloys. Good casting design and foundry techniques must be used to get full mechanical properties and consistent high quality parts. Good high temperature strength. Heat treatment is required with these alloys. Lower corrosion resistance and surface protection is required in critical applications. 7.1.1 Commercial Al-Cu cast alloy A series of casting alloys such as 85, 108, 319, and 380, classed as aluminum-copper-silicon alloys, have been developed containing less than 5% percent copper and from 3 to 8 percent silicon. 7.2 Aluminum-Silicon alloy with copper and magnesium 3xx.x It is an alloy of aluminum-Silicon alloy with Copper and/or Magnesium. They are in low cost, highest volume usage. There are three main types Al-Si-Mg, Al-Si-Cu or Al-Si-Cu-Mg. Those with copper are heat treatable. Both copper and magnesium increase strength and hardness in the as cast (f) temper and at elevated temperatures. Artificial aging is done of these alloys. Aluminum-silicon alloys that do not contain copper additions are used when good castability and good corrosion resistance are needed. If high strength and hardness are needed, magnesium additions make these alloys heat treatable. Alloys with silicon contents as low as 2% have been used for casting, but silicon content usually is between 5 and 13%. Strength and ductility of these alloys, especially those with higher silicon, can be substantially improved by modification of the Al-Si eutectic. 7.3 Binary aluminum-silicon alloys 4xx.x It is an aluminum-silicon alloy. It is based on the binary aluminum-silicon system and contains 5- 12% silicon. It has moderate strength and high ductility impact resistance. Foundry Engineering Page 14
  15. 15. Aluminum alloys 7.3.1 Example Al-Si cast alloy Aluminum-silicon casting alloys have excellent castability and resistance to corrosion. Alloy 13 (12 percent silicon) and alloy 43 (5 percent silicon) are used for intricate castings, food-handling equipment, and marine fittings. 7.4 Aluminum-Magnesium alloy 5xx.x It is an aluminum magnesium alloy. It has moderate to high strength and toughness. These alloys have high corrosion resistance especially to sea water and marine atmospheres. They can be welded and good machinability, anodized. The relatively poor castability of Al-Mg alloys and the tendency of the magnesium to oxidized increase handling difficulties, and therefore, cost. These alloys are suitable for welded assemblies and are often used in architectural and other decorative or building needs. Best corrosion resistance requires low impurity content (both solid and gaseous), and thus alloys must be prepared from high-quality metals and handled with great care in the foundry. 7.4.1 Commercial Al-Mg cast alloy The aluminum-magnesium casting alloys include alloy 214 (3.8 percent magnesium), alloy 218 (8 percent magnesium), and alloy 220 (10 percent magnesium). The first two are used for dairy and food handling equipment, fittings for chemical and sewage use, fittings for marine use, and aircraft brake shoes. Alloy 220 is the only one in this group which is age-harden-able, resulting in the highest mechanical properties of any of the aluminum casting alloys. The casting properties of alloys in this group are poor, and they require careful foundry practice. 7.5 Aluminum-Zinc alloy 7xx.x These alloys have moderate to good tensile properties in the as-cast condition. Castability of Al-Zn- Mg alloys is poor, and careful control of solidification conditions is required to produce sound, defect free castings. They are not generally recommended for service at elevated temperatures. The tensile properties of these alloys develop at room temperatures during the first few weeks after casting due to precipitation hardening. This process continues thereafter at a progressively slower rate. Heat treatments of the T6 and T7 type may be applied to the 707.0, 771.0, and 772.0 alloys 7.5.1 Commercial Al-Zn alloy The aluminum-zinc casting alloy known as 40E, containing 5.5 percent zinc, 0.6 percent magnesium, 0.5 percent chromium, and 0.2 percent titanium, provides high mechanical properties without solution treatment. This alloy also has fair casting characteristics, good, corrosion resistance, and very good machinability. It is used for aircraft fittings, turret housings, and radio equipment. Foundry Engineering Page 15
  16. 16. Aluminum alloys 7.6 Aluminum-Tin alloy 8xx.x Aluminum-tin alloys that contain about 6% Sn (and small amounts of copper and nickel for strengthening) are used for cast bearings because of the excellent lubricity imparted by tin. These tin-containing alloys were developed for bearing applications (in which load-carrying capacity, fatigue strength, and resistance, to corrosion by internal-combustion lubricating oil are important criteria). Bearings of aluminum-tin alloys are superior overall to bearings made using most other materials. Bearing performance of Al-Sn alloys is strongly affected by casting method. Fine interdendritic distribution of tin, which is necessary for optimum bearing properties, requires small interdendritic spacing, and small spacing is obtained only with casting methods in which cooling is rapid. From a foundry standpoint, the aluminum-tin alloy system is unique. In the mold, the solidification starts at about 650 °C (1200 °F), and the tin constituents of the alloy are liquid until 229 °C (444 °F). This extremely large solidification range presents unique problems. Rapid solidification rates are recommended to avoid excessive macrosegregation. 7.6.1 Commercial Al-Ti alloy Aluminum-tin casting Alloys 850.0, 851.0, and 852.0 can be cast in sand or permanent molds. However, 850.0 (6.3Sn-1Cu-1 Ni) and 852.0 (6.3Sn-2 Cu-1.2 Ni-0.8Mg) usually are cast in permanent molds. Major applications are for connecting rods and crankcase bearings for diesel engines 8 Some common casting alloys and their properties:  A242: This alloy has good fluidity and shows resistance to hot cracking and shrinkage in the casting process. It has satisfactory weldability by arc and resistance methods but brazing is not recommended. Typical applications include: motorcycle, diesel, and aircraft engine pistons, aircraft generator housings, as well as air cooled cylinder heads.  A355: An aluminum alloy with 0.02% copper added for greatly improved strength over the more common A356 material. This alloy yields highly consistent castings that are crack resistant, easy to repair, and have excellent tensile elongation properties.  A356: Aluminum alloys are characterized by very good mechanical properties and low porosity with a globular microstructure which is fine and uniform. The mechanical properties can be further improved through heat treatments such as T5 and T6. These alloys are used for casting general-purpose die castings. The common alloys used are 356-T6 for cast wheels.  A360.0: Is specified for die cast parts that require good corrosion resistance Special alloys for special applications are available, but their use usually entails significant cost premiums. . Foundry Engineering Page 16
  17. 17. Aluminum alloys  383 & 384: These alloys are a modification of 380. Both provide better die filling, but with a moderate sacrifice in mechanical properties, such as toughness.  A390: This alloy is hypereutectic aluminum-silicon alloy. The optimum structure of it must consist of fine, uniformly distributed primary Si crystals in a eutectic matrix. This alloy does not require heat treatment. The low coefficient of thermal expansion, high hardness and good wear resistance of these alloys make them suitable for internal combustion engines, pistons and cylinder blocks.  514: This alloy has a relatively poor fluidity and a high degree of directional solidification shrinkage. High pressure die casting is the primary method of forming this alloy. This combination of material properties makes 514 less casting friendly. As a result careful attention to casting geometry is essential. Because of its poor fluidity, fine detail and thin sections are difficult and radii must be large Because of shrinkage, feeding the casting requires large risers proper design. High ductility and excellent corrosion resistance is the main advantage of this alloy. It is commonly found boat propellers where impact toughness is required. References  Properties and Selection: Nonferrous Alloys and Special-Purpose Materials was published in 1990 as Volume 2 of the10 Edition Metals Handbook.  Heat Treating was published in 1991 as Volume 4 of the ASM Handbook.  Introduction to physical metallurgy Sidney H. Avner.  Heat treatment principal and techniques by C.P Sharma T.V Rajan and Ashok Sharma Foundry Engineering Page 17

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