Diffusion Bonding Of Superplastic A B Titanium Alloy

This book provides a comprehensive illustration to the superplastic forming/diffusion bonding (SPF/DB) technology developed over decades of research on titanium alloys, process modeling, and its application. SPF/DB technology plays key roles in building aviation components with complicated structures, with highly beneficial effects when well designed. With the ever-increasing demand on components with multiple layers, there is an urgent need for an updated assessment of traditional and modern SPF/DB processing methods. Success critically depends on making the most practical and effective choice of SPF/DB method for a given application. The book introduces titanium and titanium alloys, SPF/DB processing and its modeling, and applications for building typical single or multiple layer(s) structures. Particular attention is paid to illustrating the microstructure evolution during SPF/DB processes. The information for making technical decisions about optimal choice of measurement and evaluation methods is also given in the book. Each chapter follows a focused and pragmatic format. Fully illustrated throughout, the book presents the state of the art in SPF/DB technology in a manner that makes it useful for engineers to improve the established forming processes and quality of components. This book is an essential reading material for industrial practitioners, academic researchers and postgraduates.

Diffusion Beading of Materials is an attempt to pool the experience in vacuum diffusion bonding accumulated by a number of mechanical engineering works, research establishments, and colleges. The book discusses the principal bonding variables and recommended procedures for diffusion bonding in vacuum; the equipment for diffusion bonding and production rate; and the mechanization and automation of equipment. The text also describes the diffusion bonding of steels; the bonding of cast iron and cast iron to steel; and the bonding of dissimilar metals and alloys. The bonding of refractory and active metals and their alloys; the bonding of high-temperature alloys, nickel and nickel alloys; and the bonding of cemented carbides and of a cemented carbide to steel are also considered. The book further tackles the repair and reconditioning by diffusion bonding; the bonding of porous materials; and diffusion metallurgy. The text also encompasses nonmetals and their joining to metals; quality control of diffusion-bonded joints; accident prevention; and cleanliness in vacuum diffusion bonding.

There is currently great interest in the process of diffusion bonding. The main thrust has been in the joining of advanced materials such as superplastic alloys, metal matrix composites and ceramics and, most importantly, to introduce the process into mass-production operations. Diffusion bonding has also led to reduced manufacturing costs and weight savings in conventional materials and developments in hot isostatic pressing have allowed greater design flexibility. Since the first conference on Diffusion Bonding, held at Cranfield in 1987, considerable advances have been made and it was therefore considered appropriate to organise the Second International Conference on Diffusion Bonding which was held at Cranfield Institute of Technology on 28 and 29 March 1990. The meeting provided a forum for the presentation and discussion of recent developments in Diffusion Bonding and was divided into four main subject areas: steel bonding and quality control, diffusion bonding of aluminium alloys, bonding of high temperature materials and general applications. This structure is retained in the proceedings. DAVID STEPHENSON vii CONTENTS v Preface ......................... .

Rapidly solidified alloys, based upon the Al-Fe-V-Si system and designed for elevated temperature applications, were evaluated for superplasticity and diffusion bonding behavior. Alloys with 8, 16, 27, and 36 volume percent silicide dispersoids were produced; dispersoid condition was varied by rolling at 300, 400, and 500 C (572, 752, and 932 F). Superplastic behavior was evaluated at strain rates from 1 x 10(exp -6)/s to 8.5/s at elevated temperatures. The results indicate that there was a significant increase in elongation at higher strain rates and at temperatures above 600 C (1112 F). However, the exposure of the alloys to temperatures greater than 600 C (1112 F) resulted in the coarsening of the strengthening dispersoid and the degradation of mechanical properties. Diffusion bonding was possible using low gas pressure at temperatures greater than 600 C (1112 F) which also resulted in degraded properties. The bonding of Al-Fe-V-Si alloys to 7475 aluminum alloy was performed at 516 C (960 F) without significant degradation in microstructure. Bond strengths equal to 90 percent that of the base metal shear strength were achieved. The mechanical properties and microstructural characteristics of the alloys were investigated. Ting, E. Y. and Kennedy, J. R. ALUMINUM ALLOYS; DIFFUSION WELDING; DISPERSION STRENGTHENING; DISPERSIONS; FORMING TECHNIQUES; SOLIDIFICATION; SUPERPLASTIC FORMING; SUPERPLASTIC FORMING; SUPERPLASTICITY; DEGRADATION; ELONGATION; MECHANICAL PROPERTIES; MICROSTRUCTURE; SILICIDES; STRAIN RATE...

Superplastic forming and diffusion bonding is a well-established manufacturing process. It has been implemented with a variety of materials. This work specifically deals with titanium which, while being a very useful aerospace material, and is commonly used with both superplastic on diffusion bonding. It deals with the forming and bonding of double sheet structures and four sheet structures. There has been a significant amount of both experimental and theoretical work done on diffusion bonding and superplasticity with titanium. However, there has yet to be a definitive and accurate model for diffusion bonding and the effects of more complex sheet formation. Work progressed toward alleviating this knowledge gap. Several models were created with increasing complexity. Work started with more rigorous initial conditions applied to conventional bonding models. Then models were created that used conventional physics but in a freeform way to see how the voids changed without restriction on void shape. Finally, micrographs of voids were digitized and used as inputs into an energy-based phase field simulation that allowed each of the alloying elements to diffusion independently, grain growth, and for the voids to close due to strain energy. Superplasticity modelling was done using finite element methods in two and three dimensions to examine how the four-sheet forms. Research was also done to determine how one can better destructively and non-destructively test diffusion bonded specimens. The results of all this showed that while superplasticity and diffusion bonding are complex subjects there is a lot of information to gain through experiments and modelling of the process.