Preface

Titanium alloys, due to unique physical and chemical properties (mainly high relative strength combined with very good corrosion resistance), are considered as an important structural metallic material used in hi-tech industries (e.g. aerospace, space technology). Their development has led to the design of several groups of structural alloys, including single-phase α or β alloys, two-phase α+β alloys, and TiAl intermetallic alloys. Undoubtedly the consumption of titanium alloys has been continuously increasing in recent years. Although titanium and its alloys have been extensively researched for over 50 years, their application potential is still high. This has been confirmed by numerous recent publications and books presenting new findings on novel application areas for titanium alloys. This book aims to provide information on new processing methods of single- and two-phase titanium alloys.

The eight chapters of this book are distributed over four sections. The first section (*Introduction*) indicates the main factors determining application areas of titanium and its alloys. In the introductory chapter, the recent trends in design of titanium alloys and advanced technologies used for their processing are described briefly. The second section (*Manufacturing*, two chapters) concerns modern production methods for titanium and its alloys.

The next section (*Thermomechanical and surface treatment*, three chapters) covers problems of thermomechanical processing and surface treatment used for singleand two-phase titanium alloys. The fourth section (*Machining*, two chapters) describes recent results of high-speed machining of Ti-6Al-4V alloy and the possibility of application of sustainable machining for titanium alloys.

The first chapter is the introduction. The second chapter reviews the modern production methods for titanium alloys. It presents the current methods used for modern applications. The author also discuss the future development related to the most probable demands of titanium and titanium alloy products.

The third chapter is devoted to two manufacturing processes intended for commercially pure titanium: laser and mechanical forming. The chapter discusses the most important aspects related to microstructure and mechanical properties of the material and the level of residual stress in the elements after forming.

In the fourth chapter, bulk processing, including vacuum melting and hot working operations, is discussed. The sub-solvus forging is demonstrated as a method resulting in a superior combination of mechanical properties of beta titanium alloys. The chapter attempts to review the studies on manufacturing, plastic working, heat treatment, and surface modification of beta titanium alloys intended for aerospace and biomedical applications.

The fifth chapter describes the plastic flow behaviour of pseudo-alpha titanium alloy deformed at various temperatures and strain rates. The chapter presents processing maps elaborated on the basis of energy dissipation. The possibility of superplastic deformation of the examined alloy is confirmed.

**II**

**Section 4**

*by Imran Masood*

of Ti-6Al-4V ELI Alloy (Grade 23)

*and Dhananjay Vishnu Prasad Bhatt*

Machining **105**

**Chapter 7 107**

**Chapter 8 123**

Sustainable Machining for Titanium Alloy Ti-6Al-4V

The Comparison of Cutting Tools for High Speed Machining

*by Chakradhar Bandapalli, Bharatkumar Mohanbhai Sutaria* 

The sixth chapter refers to solid-solution hardening of surface layers of titanium alloys (α, near-α, α+β) due to diffusional saturation in a gas medium containing oxygen. The authors have determined the relationship between parameters of surface-hardened layers (surface hardness, depth of hardened zone, microstructure) obtained by various surface hardening methods and fatigue properties of examined titanium alloys.

The seventh chapter deals with the high-speed micro-milling process used to achieve the desired surface finish without traditional coolants. The investigation of various tool (uncoated & PVD coated AlTiN, TiAlN tungsten carbide) wear behaviour in the milling process under dry cutting conditions of Ti-6Al-4V ELI alloy is presented. Analysis of cutting force and wear mechanisms is performed for examined mills.

In the eighth chapter, an analysis of the machining process of Ti-6Al-4V alloy, both dry and using conventional and cryogenic cooling, is presented. The assessment of machining sustainability is based on the following variables: cutting power, machining time, machining cost, material removal rate, and cutting tool life.

We hope that the recent research data and reviews presented in this book will contribute to the improvement of operational properties and the increase of the range of applications of titanium and its alloys.

> **D.Sc. Maciej Motyka, Ph.D. Waldemar Ziaja and Prof. Jan Sieniawski** Department of Materials Science, Faculty of Mechanical Engineering and Aeronautics of the Rzeszow University of Technology, Rzeszow, Poland

> > **1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

Applications

casting and plastic working processes [1–5].

**1. Introduction**

Introductory Chapter: Novel

Aspects of Titanium Alloys'

*Maciej Motyka, Waldemar Ziaja and Jan Sieniawski*

Titanium is characterized by unique physical and chemical properties determining its specific applications. Since it was discovered in 1791 by William Gregor, its production was considered difficult and unprofitable for almost 150 years. In 1940, William J. Kroll developed commercially attractive production method based on the reduction of TiCl4 using Na or Mg. Kroll process, in substantially unchanged form, is still the dominant process for titanium production. Titanium sponge is remelted (e.g., in vacuum arc process—VAR) to the form of commercial pure (CP) titanium or titanium alloys. Ingots are usually primarily processed by homogenization annealing or plastic working in the β-phase field. Products can be manufactured by

Titanium alloys—comparing with other structural materials—are characterized by high relative strength in the wide temperature range and very good corrosion resistance in many chemically aggressive environments. Such properties create many possibilities of improvements of technological processes, tooling and products in various industry branches. The main application areas of titanium alloys include transportation (mainly aerospace industry), chemical, food, machine building, papermaking, electrotechnics, electronic, fuel-energetic, metallurgical industries, and also geology and medicine [6]. Mechanical properties of titanium alloys are developed in plastic working and heat treatment processes, causing intentional microstructure evolution. It should be pointed that obtaining finished products having desired microstructure and properties is difficult due to some of the properties of titanium alloys, such as: high chemical affinity to oxygen, low thermal conductivity, high heat capacity and significant dependence of plastic flow resistance on strain rate. Quite often, hot-worked titanium products are characterized by various deformation conditions leading to formation of zones having various phase composition and dispersion and therefore various mechanical properties [7]. The main types of microstructure in two-phase titanium alloys are lamellar consisting of colonies of α-phase lamellae within β-phase grains of several hundred microns in diameter (formed after slow cooling when deformation or heat treatment takes place at a temperature above the β-transus)—and equiaxed—consisting of globular α-phase dispersed in β-phase matrix (formed after deformation in the two-phase α + β field). Alloys having lamellar microstructure are characterized by relatively low tensile ductility, moderate fatigue properties and good creep and fatigue crack growth resistance, whereas in case of equiaxed microstructure, materials have a better balance

of strength and ductility at room temperature and fatigue properties [8].
