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This memorandum describes the fusion-welding characteristics, mechanical properties, and stress-corrosion behavior of high-strength, weldable aluminum alloys. These are defined as alloys in which sound welds can be produced and in which at least 50 and 70 percent of the maximum base-metal strength can be retained in the as-welded and post-weld-treated conditions, respectively. Careful selection of joining method and filler metals as well as close control of joining-process parameters is necessary to produce high-strength aluminum weldments. Highest strengths and weld-joint efficiencies in high-strength weldable alloys are achieved with the use of postweld aging and/or mechanical treatments. The best combination of highest strengths and good welding characteristics is found in the 2000 and 7000 alloy series. As compared with the 2000 and 5000 alloy series, the 7000 alloy as a class suffer three major property disadvantages: (1) their tendency to be notch sensitive, (2) their tendency to exhibit low toughness at low temperatures, and (3) their much greater susceptibility to stress-corrosion cracking. Nonetheless, several relatively new 7000 series alloys have been developed which show reasonably good notch toughness to -423 F and which are considered competitive with the 2219 and 2014 alloys for cryogenic applications. (Author).
The purpose of this report is to summarize the present state of aluminum-welding technology. The major topics covered are: Basic metallurgy of various heat-treatable and non-heat-treatable alloy classes; welding processes used for joining aluminum with emphasis on newer processes and procedures which are considered important in defense metals industries; welding characteristics of various alloys; comparison of tensile properties, cracking tendencies, notch toughness, and stress-corrosion characteristics of various weldments; dissimilar metal welds; and causes of porosity and cracking of aluminum welds and the effect of porosity on weld strength. (Author).
This book reviews the behaviour of metals and alloys during welding. In the first part the heat flow in arc welding processes is discussed. The weld thermal cycle is explained in terms of heat input, and the geometry of weld and thicknesses to be welded. The real welding cycle is described in terms of thermal and strain cycles. The weld metal is characterized in terms of fusion stage, absorption of gases and stage of metal crystallization and structural transformation. The metallurgical background of cracking is described by a full set of crackability tests along with the evaluation of metals from the point of view of crackability. Post welding heat treatment is reviewed, and includes the relaxation of stresses induced by welding. Guidelines are given for the selection of steels for welded structures. Several chapters examine the weldability of particular steels, including high strength steels, stainless steels, high alloyed steels, cryogenic steels and other metals and alloys. The theories are quantified in the form of calculations or computing programmes. Readers will find sufficent data for software processing.
The application of aluminium-lithium alloys over a wide range of engineering technologies will require development of both effective methods for joining these materials and through understanding of their welding metallurgy. This chapter covers the pertinent literature regarding the weld metal porosity, susceptibility to cracking during welding, eqiaxed zone formation and associated fusion boundary cracking, mechanical properties and corrosion behaviour of welds. Microstructural modification is especially attractive for alloys with pronounced hot cracking susceptibility. Aluminum–lithium alloys are one such class of materials. Since the hot cracking tendency is known to be a function of weld metal composition, several crack resistant filler materials such as AA 2319, AA 4043 and AA 5356 are in common use. While primary approach to the problem is thus to modify weld metal chemistry, a secondary solution is to reduce the coarseness of the solidification structure. Of the various techniques available for modifying the structure, pulsed current, magnetic arc oscillation techniques of gas tungsten arc welding and inoculation using grain refining additions offers the greatest promise for practical applications. Improving weldability of these alloys through modification of fusion zone microstructure are covered in this chapter. Lastly, solid state welding processes such as friction and friction stir welding of Al-Li alloys are briefly discussed.
This book is a guide for applying fundamental knowledge of welding metallurgy and weldability principles to the practical selection of materials, welding processes and process parameters, and post-weld processing to optimize weld properties and performance. It also provides insight into conducting failure analysis of welded lightweight alloy structures. This is followed by an in-depth discussion of the influence of alloy chemical composition, welding process and associated thermal cycles on weld solidification, solid-state phase transformations, microstructure evolution and mechanical properties. The origin and prevention of weld defects such as porosity are also presented. In addition, the book provides insight into conducting failure analysis of welded lightweight ally structures.
Describes the weldability aspects of structural materials used in a wide variety of engineering structures, including steels, stainless steels, Ni-base alloys, and Al-base alloys Welding Metallurgy and Weldability describes weld failure mechanisms associated with either fabrication or service, and failure mechanisms related to microstructure of the weldment. Weldability issues are divided into fabrication and service related failures; early chapters address hot cracking, warm (solid-state) cracking, and cold cracking that occur during initial fabrication, or repair. Guidance on failure analysis is also provided, along with examples of SEM fractography that will aid in determining failure mechanisms. Welding Metallurgy and Weldability examines a number of weldability testing techniques that can be used to quantify susceptibility to various forms of weld cracking. Describes the mechanisms of weldability along with methods to improve weldability Includes an introduction to weldability testing and techniques, including strain-to-fracture and Varestraint tests Chapters are illustrated with practical examples based on 30 plus years of experience in the field Illustrating the weldability aspects of structural materials used in a wide variety of engineering structures, Welding Metallurgy and Weldability provides engineers and students with the information needed to understand the basic concepts of welding metallurgy and to interpret the failures in welded components.
Friction Stir Welding of High Strength 7XXX Aluminum Alloys is the latest edition in the Friction Stir series and summarizes the research and application of friction stir welding to high strength 7XXX series alloys, exploring the past and current developments in the field. Friction stir welding has demonstrated significant benefits in terms of its potential to reduce cost and increase manufacturing efficiency of industrial products in transportation, particularly the aerospace sector. The 7XXX series aluminum alloys are the premium aluminum alloys used in aerospace. These alloys are typically not weldable by fusion techniques and considerable effort has been expended to develop friction stir welding parameters. Research in this area has shown significant benefit in terms of joint efficiency and fatigue performance as a result of friction stir welding. The book summarizes those results and includes discussion of the potential future directions for further optimization. Offers comprehensive coverage of friction stir welding of 7XXX series alloys Discusses the physical metallurgy of the alloys Includes physical metallurgy based guidelines for obtaining high joint efficiency Summarizes the research and application of friction stir welding to high strength 7XXX series alloys, exploring the past and current developments in the field