Preface

Constant progress in engineering in the area of advanced structures and technologies for aerospace and power industry, medicine, automatics and mechatronics, manufacturing of control and measurement equipment, is driven to a large extent by development and appli‐ cation of new or modified functional materials. It includes titanium and its alloys, although initially they were intended mainly for use as a structural material for load, carrying air‐ frame elements of aircraft and helicopters.

Titanium enables implementation of new solutions in structures and technologies due to its unique combination of physical, chemical and mechanical properties. First of all, it has a low density, high strength properties and good corrosion resistance in many chemical environ‐ ments. Titanium is also characterized by low thermal conductivity and thermal expansion, high friction coefficient and propensity for seizure.

During the last decades, extensive research efforts have been concentrated on the evolution and control of the titanium alloys microstructure through adjustment of the processing pa‐ rameters in order to obtain desirable balance of properties for specific applications.

Simultaneously, there was significant development of the methods for obtaining better properties of the surface layer of the elements made of titanium and its alloys. The aim was to increase hardness, prevent seizure in case of machine kinematic pairs and also to increase biocompatibility and corrosion resistance of medical implants in human body. The results of the studies falling into both subject areas are presented in this publication.

The book contains six chapters and covers topics dealing with biomedical applications of titanium alloys, surface treatment, relationships between microstructure and mechanical and technological properties, and the effect of radiation on the structure of the titanium al‐ loys.

In the first chapter application of titanium alloys in orthopaedics is explored with emphasis on strategies for enhancing their bioactivity and promoting osseointegration of the implants.

The second chapter deals with techniques for surface modification of medical implants lead‐ ing to their prolonged use. The results of the studies on the influence of sputtered hydroxya‐ patite and SiO2 nanocoatings on titanium are discussed.

In the third chapter the processes of diffusive saturation of titanium by interstitial elements are modeled taking into account interaction of titanium with nitrogen and oxygen. The po‐ tentials of the model for estimating the effects of thermo-chemical treatment are discussed.

In the fourth chapter the relationships between processing parameters, morphology of the microstructure characterized by quantitative stereological parameters of microstructure and mechanical properties of selected high strength two-phase titanium alloys are summarized.

In the next chapter the formability of titanium alloys is discussed on the example of Ti-6Al-4V alloy. Forming limit diagrams are determined experimentally in the hydroforming bulge test and numerically, using finite element method and various constitutive models.

In the final chapter the influence of the radiation and others factors like plastic deformation and thermo-chemical treatment on the structure and crystal lattice defects in binary titanium alloys is investigated.

> **Prof. Jan Sieniawski** Faculty of Mechanical Engineering and Aeronautics of the Rzeszów University of Technology

**Chapter 1**

**Titanium Alloys in Orthopaedics**

Additional information is available at the end of the chapter

**1.1. Development of titanium alloys for use in orthopaedics**

Metallic implants are commonly used in the orthopedic field. Despite the large number of metallic medical devices in use today, they are predominantly make up of only a few metals. Metallic alloys such as titanium continue to be one of the most important components used in orthopaedic implant devices due to favorable properties of high strength, rigidity, fracture toughness and their reliable mechanical performance as replacement for hard tissues. Ortho‐ paedic implants are medical devices used for the treatment of musculoskeletal diseases and may consist of a single type of biomaterial or comprise a number of different biomaterials working together in modular parts. Prime examples of titanium implants used in orthopaedics would include prosthetic hip and knee replacements for various types of arthritis affecting these joints, spinal fusion instruments for stabilizing degenerate and unstable vertebral segments, and fracture fixation devices of various types such as plates, screws and intrame‐ dullary rods. Although titanium based implants are typically expected to last ten years or more, however longevity is not assured and the lack of integration into the bone for long-term survival often occurs and leads to implant failure. Revision surgery to address such failure involves increased risk, complications and costs. The main reason for the failure of these implants is aseptic loosening which accounts for 60 to 70% of the cases for revision surgery. The success of implants is dependent on firm bonding or fixation of implant biomaterial to bone, for optimal function and lastingness. Therefore one of the key challenges in bone healing and regeneration is the engineering of an implant that incorporates osseointegration with enhanced bioactivity and improved implant-host interactions so as to reduce biological related

Titanium alloys, originally used for aeronautics, garnered attention from the biomedical field, due to their biocompatibility, low modulus of elasticity, and good corrosion resistance.

> © 2013 Wang and Poh; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Wang and Poh; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Wilson Wang and Chye Khoon Poh

http://dx.doi.org/10.5772/55353

**1. Introduction**

implant failure.
