Investigation on Hot Cracking of Aluminum 7xxx Alloy Using Gas Tungsten Arc Welding
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Food packaging, structural components in the aerospace industry, and other uses for aluminized aluminium alloys are just a few of the many uses for this abundant metal. Because of its low weight, moderate strength, and high corrosion resistance, aluminium and its alloys have found widespread use in a wide range of industries. Aluminum alloys of the 7xxx series have superior mechanical qualities when compared to other aluminium alloy series. The alloy AA7075 is utilised in the structure of aircraft wings. When fusion welding is used to combine certain alloys, they are more prone to solidification or hot cracking. The alloying components present contribute to these alloys' high crack sensitivity. Thus, a rigorous analysis has been undertaken in this project effort to determine how to reduce the susceptibility of the alloy 7075 to hot cracking by adjusting the composition without affecting the mechanical qualities. A thorough background study has been conducted on the effect of hot cracking on the aluminium alloy AA7075, and a methodology for overcoming this welding defect has been developed. This methodology includes altering the composition of the major alloying elements in AA7075 and stabilising the composition for the development of a new alloy. Experiments were conducted and alloys were cast with a predetermined composition. The samples were subjected to a hot cracking test, and the sample with the best result had its mechanical properties determined. The test results were compared to those obtained with AA7075 and discussed in this paper.Keywords:
6063 aluminium alloy
Fusion welding
Alonizing
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Fusion welding
Weldability
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Magnesium based alloys are being considered currently as replacements for aluminum alloy components in automobile industry, due to their high specific strength as compared to aluminum alloys. However, the utilization of Mg alloys is restricted due to their poor formability, and consequently these have been used mostly in the as cast condition. In order to increase the utilization of the wrought forms, it is necessary to develop optimum deformation processing conditions for producing defect free wrought products economically from the cast alloys. In the present study, the compressive deformation characteristics of as cast Mg-2wt% Al alloy with an equiaxed initial grain size of 150 +/- 10 mum have been studied in the temperature range of 573-723 K and at strain rates ranging from 10(-2) to 10 s(-1). The results are analyzed in terms of the existing theoretical hot working models together with the microstructural characteristics of the alloy. Furthermore, optimum. conditions for subsequent deformation processing have been identified based on a combination of mechanical data together with the deformed microstructures.
Equiaxed crystals
Thermomechanical processing
6063 aluminium alloy
Alonizing
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Aluminium and its alloys are widely used in brazing various components in automotive industries due to their properties like lightweight, excellent ductility, malleability and formability, high oxidation and corrosion resistance, and high electrical and thermal conductivity. However, high machinability and strength of aluminium alloys are a serious concern during casting operations. The generation of porosity caused by dissolved gases and modifiers affects seriously the strength and quality of cast product. Brazing of Al and its alloys requires careful monitoring of temperature since theses alloys are brazed at around the melting temperature in most of the aluminium alloys. Therefore, the development of low temperature brazing filler alloys as well as superior strength Al alloys for various engineering applications is always in demand. In various heat exchangers and automotive applications, poor strength of Al alloys is due to the inherent porosities and casting defects. The unstable mechanical properties is therefore needed to be controlled by adding various additive elements in the aluminium and its alloys, by a change in the heat treatment procedure or by modifying the microstructure. In this regard, this article reports the effect of various elements added in aluminium alloys to improve microstructure, brazeability, machinability, castability as well as to stabilize the mechanical properties.
Machinability
Brazing
Castability
Ductility (Earth science)
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For last several decades aluminium and aluminium alloys are widely used in automotive industries because for their favourable properties like low density (about 2700 Kg/m 3 ), good malleability, high formability, high corrosion resistance and high electrical and thermal conductivity. High machinability and workability of aluminium alloys are prone to porosity due to gases dissolved during melting processes. However, in the engineering application pure aluminium and its alloys still have some problems such as relatively low strength, unstable mechanical properties and low wear resistance. The microstructure can be modified and mechanical properties, wear resistance can be improved by alloying, cold working and heat treatment. In this regards, the present paper reports the influences of enhancement of magnesium contents on the mechanical properties and wear behavior of LM 6 aluminum alloy. Index Terms: LM 6 Aluminum alloy, wear rate 1. Introduction: Aluminium and aluminium alloy are gaining huge industrial significance because of their outstanding combination of mechanical, physical and tribological properties over the base alloys. These properties include high specific strength, high wear and seizure resistance, high stiffness, better elevated temperature strength, controlled thermal expansion coefficient and improved damping capacity (1). These properties obtained through addition of alloying elements, cold working and heat treatment. Alloying elements are selected based on their effects and suitability. For the purpose of understanding their effects and importance, alloying elements for majority of alloys are best classified as major and minor elements, microstructure modifiers or impurities, however the impurity elements in some alloys might be major elements in others (2). LM6 is one of the most important Aluminium alloy falls under Aluminium - Silicon alloying system in which aluminium is the predominant metal and high levels of silicon (4% to 13%) are added that contributes to give good casting characteristics and increases fluidity, by which we can produce castings of thick as well as thin sections according to the required design. Other typical alloying elements are Copper, Magnesium, Manganese, Silicon, Zinc, Iron, Nickel, Lead and Tin.
Specific strength
6063 aluminium alloy
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The commercial 7000 series aluminium alloys are based on medium strength Al–Zn–Mg and high strength Al–Zn–Mg–Cu systems. The medium strength alloys are weldable, whereas the high strength alloys are non-weldable. This is because the amount of copper present in these alloys gives rise to hot cracking during solidification of welds. As a result, the high strength Al–Zn–Mg– Cu base alloys are not used for applications where joining of components by welding is an essential step. In the present study, using a combination of qualitative Houldcroft test and quantitative Varestraint test, it is shown that a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process. The improvement in weldability is found to be the result of the considerable grain refinement in the weld structure following the scandium addition. The results of microhardness and tensile tests are further described within the context of the present work to demonstrate that the 7010+Sc welds also exhibit a combination of improved strength and ductility.
Weldability
Scandium
Charpy impact test
Ductility (Earth science)
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Alonizing
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Base metal
Austenitic stainless steel
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Friction welding is a solid state joining process and is widely being considered for aluminum alloys. 7075 is an aluminum alloy, with zinc as the primary alloying element. Due to its strength, high density, thermal properties, High strength precipitation hardening, 7075 aluminum alloys are extensively used in aerospace industry. It has good fatigue strength and average mach inability, but has less resistance to corrosion than many other Al alloys. These alloys are difficult to join by conventional fusion welding techniques. This paper aims at exploring the possibility of welding this alloy using friction welding. Tensile Strength, Hardness values, Flash parameters with respect to upset pressure and Microstructure of the 7075 were studied.
Weldability
Friction Welding
Fusion welding
Alonizing
6063 aluminium alloy
Upset
Plastic welding
Precipitation hardening
Friction Stir Welding
Hardening (computing)
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The ever increasing demand from aerospace industries and automotive industries to manufacture components which are lighter and stronger than conventional steel has prompted the significant usage of aluminium alloys. This research work involves the investigation of mechanical properties in aluminium alloys before and after cold work forged. Major alloying elements used in the aluminium alloy are manganese and silicon. The aluminium alloy ingots are prepared through gravity casting. After the ingots are air cooled to room temperature, they are work hardened using cold forging method. The cold forged aluminium alloys are then subjected to tensile tests, wear tests, hardness tests and microstructure analysis using optical Scanning Electron Microscope (SEM). The material properties achieved are compared with the alloys properties that have not been subjected to work hardening. The expected outcome is to achieve a work hardened aluminium alloy that exhibits excellent wear resistance property which can be best suited for numerous industrial manufacturing requirements. It is observed that broken Mn after forging has shown better wear resistance property having toughness property.
6063 aluminium alloy
Work hardening
Die casting
Tensile testing
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