Friction Stir Welding of Dissimilar Alloys and Materials (eBook)

Nilesh Kulkarni, Rajiv S. Mishra, Wei Yuan (Autoren)

eBook Download: PDF | EPUB

2015 | 1. Auflage
134 Seiten
Elsevier Science (Verlag)
978-0-12-802621-2 (ISBN)

Infos

This book will summarize research work carried out so far on dissimilar metallic material welding using friction stir welding (FSW). Joining of dissimilar alloys and materials are needed in many engineering systems and is considered quite challenging. Research in this area has shown significant benefit in terms of ease of processing, material mixing, and superior mechanical properties such as joint efficiencies. A summary of these results will be discussed along with potential guidelines for designers.

• Explains solid phase process and distortion of work piece
• Addresses dimensional stability and repeatability
• Addresses joint strength
• Covers metallurgical properties in the joint area
• Covers fine microstructure
• Introduces improved materials use (e.g., joining different thicknesses)
• Covers decreased fuel consumption in light weight aircraft
• Addresses automotive and ship applications

Nilesh. N. Kulkarni completed his M.E. (electronics and telecommunication) from All India Shri Shivaji Memorial Society's Institute of Information Technology, Pune. His areas of interests include biomedical signal and image processing, pattern recognition, and machine learning. Presently, he is working on biomedical signal processing applications. He is a member of IETE and IEI, India and a member of the IEEE.

Textauszug

Chapter 1

Introduction

With increased pressure for high performance on engineering structures being used in a number of ground, sea, and aerospace applications, there is need for not only advanced materials but also efficient joining techniques capable of producing high-integrity joints, even between dissimilar materials. In the past two decades, friction stir welding (FSW) (a solid-state welding technique) has emerged as a potential candidate for dissimilar materials welding. This chapter summarizes areas where, for the development of efficient engineering structures, dissimilar material welding is needed. A brief description of FSW technology has been provided, and key areas where FSW can be applied in future for dissimilar material welding have been identified.

Keywords

Friction stir welding; dissimilar material welding; fusion welding; welding; joining

Humans and materials have flocked together since the humans have roamed the earth. As a matter of fact, the influence of materials on human civilization has been so profound, our progress is sometimes described in terms of materials—stone age, copper age, bronze age, and iron age. Industrial revolution was a major turning point in the history of human civilization which propelled the development of new materials. New materials enabled building of stronger and cheaper artifacts used in a variety of situations such as ground, sea, and aerospace transportation-related applications. The twentieth century witnessed a phenomenal growth on the materials development front, and designers of engineering structure were presented with a monumental task of selecting an appropriate or a set of materials for a particular component. On the one hand the availability of a wide spectrum of materials allowed designers to be very creative with the design of any component, on the other it posed a new set of challenges in terms of integrating different types of materials in a single structure. Among many, the assembly of components made of materials widely differing in chemical, thermal, physical, and mechanical properties became a challenge. For the majority of dissimilar materials, mechanical fastening is an appropriate choice. But the demand on high-performance structures has shifted attention from mechanical joining such as riveting and bolting to welding. Although a great number of welding techniques have been developed so far to deal with different types of materials, the welding of dissimilar materials still remains a challenge.

1.1 Examples of Engineering Systems Needing Dissimilar Joints

The need for joining dissimilar materials often arises in industrial applications due to demand for a wide variety of materials to impart complex shape, different loading or performance conditions needed in different parts of the assembly such as high strength and corrosion resistance. Materials have been the backbone for industry, and advanced lightweight materials are essential especially for transportation industries to improve fuel economy while maintaining or improving safety and performance. Steels, owing to their attractive properties, recyclability, matured state of the art, and relatively low cost, have historically been the preferred choice for structural application in automotive industry. However, it is becoming clear that not a single material can fit all applications. The multi-material concept including a hybrid of light metals is now a trend for the automotive industry (Figure 1.1). With extra push toward the use of light materials, the fraction of light materials including polymer matrix composites is poised to increase in the near future. Traditional steel components can be replaced or partially replaced with lighter materials such as advanced high-strength steel, aluminum alloys and polymer.

Figure 1.1 Material distribution of total vehicle curb weight in kilogram (Mayyas et al., 2012).

One area where dissimilar material joint is essential in a structure is the fabrication of tailor-welded blank (Figure 1.2). A tailor-welded blank consists of joining sheets of different materials and/or the same material with different thicknesses, which is then submitted to a stamping process to form into the desired shape. Tailor-welded blanks are primarily used in the automotive industry and offer a significant potential on weight reduction for applications such as side frames, doors, pillars, and rails, because no reinforcement is required. The main advantage of a tailor-welded blank is that it allows the joining of multiple pieces to fabricate much larger components as well as proper distributions of weight and material properties in the final stamped part with a consequent reduction in weight and cost.

Figure 1.2 Tailor-welded blanks for automotive application (http://automotive.arcelormittal.com/tailoredblanks/TB_products/Applications, last accessed on 01.12.15).

In addition to the body structure, there are also components and devices in an automobile consisting of dissimilar material joints, such as powertrain components. Figure 1.3 presents a turbocharger impeller for high-efficiency gas and diesel engines. The impeller is made of carbon steel and Inconel and welded by using electron beam. The dissimilar material assembly enables the lightweight design as well as superior performance.

Figure 1.3 (A) Turbocharger impeller made of carbon steel (shaft) and Inconel (impeller). (B) Magnified view of the weld between shaft and impeller (http://www.ptreb.com/industries/automotive/turbocharger_impeller_welding/, accessed on 30.11.14).

Advanced materials, structures, and fabrication technologies are needed to enable the design and development of advanced future aircraft especially in airframe and propulsion systems. The high-performance materials such as titanium alloy and nickel-based superalloy, and adaptive materials such as piezoelectric ceramics, shape memory alloys, shape memory polymers, and carbon fibers, can only be used where they are essential. To integrate these materials into airframe and/or aircraft engine structures, development of joining and integration technologies including metal to metal and metal to ceramic is critical (Figure 1.4).

Figure 1.4 Aircraft engine with multifunctional materials (Campbell, 2006).

Figure 1.5 shows a schematic of pressurized light-water nuclear reactor showing the use of an array of different high-temperature materials in the primary and secondary circuits including the reactor. It is appreciated that materials with better performance would be needed in reactors being designed for longer lifetime and superior capability. Similar need is being felt in the development of ultra-supercritical steam boilers expected to operate at 760°C and 35 MPa. The current design allows boilers to operate at 620°C and 20 MPa (Sridhar et al., 2011). Again, to meet increased expectation from the materials will require not only development of materials with increased performance but also development and use of advanced integration technologies.

Figure 1.5 A schematic diagram showing different parts of a pressurized light-water nuclear reactor and materials used in the construction (Zinkle and Was, 2013).

Above examples taken from various industries show that a wide range of materials are needed for successful performance of engineering structures. A large number of components made of different materials are integrated to give rise to the final structure. A number of engineering solutions are available to assemble subsystems and choice of which depends on a number of factors including availability, cost, and performance expected from the system.

1.2 Conventional Joining Techniques

Figure 1.6 shows a few commonly used joining techniques for similar and dissimilar materials. Among all the advantages of welding include cheaper and faster integration time, flexibility in design, weight savings, higher structural stiffness, high joint efficiency, air and water tightness, and no limit on the width which can be welded together. Conventionally both fusion welding and solid-state welding techniques have been used to join dissimilar materials. Solid-state welding techniques include friction stir welding (FSW), ultrasonic welding, explosion welding, and diffusion welding. Brazing and soldering also have been tried to create joints between dissimilar welds.

Figure 1.6 Various techniques used to join similar and dissimilar materials.

1.3 Disadvantages of Conventional Welding Techniques for Dissimilar Materials

Although the majority of the issues encountered in the dissimilar metal welding using fusion welding techniques are present in solid-state welded joints, it is less severe in solid-state welds. Some of the advantages of the solid-state weld over fusion welds with regard to similar welds still hold good during dissimilar material welding—for example, the absence of porosity and less distortion during solid-state welds. Due to high temperature during fusion welding compared to solid-state welding, most of the time the use of filler material results in a weld material where metallurgical characteristics, mechanical, and physical properties are totally different from individual materials used in dissimilar welds. Some of the issues faced during solid-state welding and fusion welding are depicted in Figure 1.7.

Figure 1.7 A few issues commonly encountered in dissimilar metal...

Produkt-Details

• Erscheint lt. Verlag: 5.3.2015
• Sprache: englisch
• Themenwelt: Technik ► Bauwesen
• Themenwelt: Technik ► Maschinenbau
• ISBN-10: 0-12-802621-9 / 0128026219
• ISBN-13: 978-0-12-802621-2 / 9780128026212