Friction Stir Processing of Aluminium Alloy Using Multipass Technique E-Book

Dr. Chandan Deep Singh

• Herausgeber: BookRix
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2018

Beschreibung

FSP is manufacturing the Technique used to modify the microstructure metals. In this process a rotating tool is penetrated in the work piece and moved in the transverse direction. Further FSP technique is used for fabrication of surface composite on aluminium substrate and homogenization of powder metallurgy aluminium alloy, metal matrix composites, and the cast aluminium alloys. By this process material properties can be improved due to enhancement of grain structure. With this technique the material have shown good corrosion resistance, high strength and high fatigue resistance.

Leseprobe

Dr. Chandan Deep Singh, Rajdeep Singh

Friction Stir Processing of Aluminium Alloy Using Multipass Technique

BookRix GmbH & Co. KG80331 Munich

Chapter 1

CHAPTER 1

INTRODUCTION

Friction Stir Processing

FSP is manufacturing the Technique used to modify the microstructure metals. In this process a rotating tool is penetrated in the work piece and moved in the transverse direction.

Further FSP technique is used for fabrication of surface composite on aluminium substrate and homogenization of powder metallurgy aluminium alloy, metal matrix composites, and the cast aluminium alloys. By this process material properties can be improved due to enhancement of grain structure. With this technique the material have shown good corrosion resistance, high strength and high fatigue resistance.

Fig 1.1 A FSP process (http://en.wikipedia.org/wiki/Friction_stir_processing)

Friction stir processing is a method of changing the properties of a metal through intense, localized deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat effected zone typical of fusion welding.When ideally implemented, this process mixes the material without changing the phase and creates a microstructure with fine, equixed grains. This homogeneous grain structure, separated by high-angle boundaries, allows some aluminium alloys to take on superplastic properties. Friction stir processing also enhances the tensile strength and fatigue strength of the metal. In tests with actively cooled magnesium-alloy work pieces, the microhardness was almost tripled in the area of the friction stir processed seam. (http://en.wikipedia.org/wiki/Friction stir processing)

It is widely used in aerospace industries and used in automobile industry for making body panels, for cycle frames and other components, these alloys are used for boat building and shipbuilding, It is used for architectural fabrication, particularly window frames, door frames, roofs, and sign frames. Furthermore, the FSP technique has been used for the fabrication of a surface composite on aluminium substrate and the homogenization of powder metallurgy (PM) aluminium alloys, metal matrix composites, and cast aluminium alloys. Compared to other metalworking techniques, FSP has distinct advantage

Fig 1.2 A FSP Machine – 3 axis (Mishra et al., 2005)

Friction Stir Welding (FSW) is being targeted by modern industries for structurally demanding applications providing high-performance benefits. FSW has been shown to strongly decrease severe distortion and residual stresses compared to the traditional welding processes. The Frictioned zone consists of a weld nugget, a thermo-mechanically affected zone and a heat affected zone. The process results in obtaining a very fine and equiaxed grain structure in the weld nugget causing a higher mechanical strength and ductility. Jata and Semiatin showed that the microstructure in the weld nugget zone evolves through a continuous dynamical recrystallization process, the strong grain refinement produced by the process leads the microstructure to the fine dimensions offering the possibility to exhibit superplastic properties.

Fig 1.3 A Robotic FSP Machine – 6 axis (Mishra et al., 2005)

Such technology requires a thorough understanding of the process and consequent mechanical properties of the heavily deformed material in order to be used in the production of components for aerospace applications and for this reason detailed research and qualification work is required. In the FSP, a rotating tool with a specially designed rotating probe travels down the surfaces of metal plates, and produces a highly plastically deformed zone through the associated stirring action. The localized thermo-mechanical effected zone is produced by friction between the tool shoulder and the plate top surface, as well as plastic deformation of the material in contact with the tool. The probe is typically slightly shorter than the thickness of the work piece and its diameter is typically the thickness of the work piece. The FSP process is a solid state process and therefore a solidification structure is absent and the problem related to the presence of brittle inter-dendritic and eutectic phases is eliminated. In addition the strong grain refinement and the possibility to obtain a uniform microstructure has lead researchers to investigate the possibility to employ such a process to increase the superplastic properties of some aluminium alloys. In FSP the work piece does not reach the melting point and the mechanical properties of the material are much higher compared to the traditional techniques, in fact, the undesirable microstructure resulting from melting and re-solidification, characterized by low mechanical properties, is absent leading to improved mechanical properties such as ductility and strength in some alloys. (Cavaliere et al., 2005)

Friction stir processing (FSP) is a unique technique for refining and modifying the microstructure of materials. In many aspects, the basic principles of FSP are the same as those of FSW. Besides, FSP has been successfully used for fabricating the surface composites, for refining the surface microstructures of various materials as well as for synthesizing the composite and intermetallic compounds.

Friction stir processing is based on the friction stir welding (FSW) technique which was invented by The Welding Institute (TWI) in 1991. On observing the advantages associated with FSW, mainly grain refinement, the phenomenon has been extended to processing of commercial alloys. Friction stir processing (FSP) is a solid-state process in which a specially designed rotating cylindrical tool, consisting of a pin and a shoulder, is plunged into the sheet. The tool is then traversed in the desired direction. The rubbing of the rotating shoulder generates heat which softens the material (below the melting temperature of the sheet) and with the mechanical stirring caused by the pin, the material within the processed zone undergoes intense plastic deformation yielding a dynamically recrystallized fine grain structure. Despite the large number of studies that are being conducted to advance FSP technology, the effects of FSP on various mechanical and microstructural properties are still in need for further investigations. In addition, correlations between FSP parameters, mechanical properties and microstructural characteristics are not yet well understood. Accurate correlations are needed for successful modeling and process optimization. Most of the work that has been done in the field of friction stir processing focuses on aluminium alloys. (Darras et al., 2007)

Friction stir processing (FSP), developed based on the basic principles of friction stir welding

(FSW), a solid-state joining process originally developed for aluminium alloys, is an emerging metal working technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed. (Ma et al., 2008)

Fig 1.4 FSP Tool movement