Ti–6Al–4V–0.5B—A Modified Alloy for Implants Produced by Metal Injection Molding

Abstract

Permanent implants have to fulfill a great variety of requirements related to both material and geometry. In addition, manufacturing costs play a role, which is getting steadily more and more important. Metal Injection Molding (MIM) of titanium alloy powders may contribute to the development of implants with higher functionality without increasing the price. High degree of freedom with regard to geometry, high material efficiency, and the possibility to create even porous structures are main benefits from applying this technique. Today, even long‐term implants made from Ti–6Al–4V by MIM are commercially available. However, in order to improve fatigue behavior it is beneficial to perform a minor variation of Ti–6Al–4V by adding a low amount of boron. In this paper the mechanical, biological, and corrosion properties of specimens manufactured from Ti–6Al–4V–0.5B alloy by MIM are presented. In order to exclude unknown reactions in the body environment due to the boron content, corrosion, and biological tests are performed. Tensile and fatigue tests characterize the mechanical properties. Potentiodynamic polarization and electrochemical impedance spectroscopy are done in comparison to wrought and to MIM processed Ti–6Al–4V material. For cell experiments cancellous bone cells are cultured to perform adhesion, proliferation, and viability experiments. The results presented here show that the alloy Ti–6Al–4V–0.5B satisfies all basic needs of a material for highly loaded permanent implants manufactured by MIM.

From titanium to magnesium: processing by advanced metal injection moulding

“…First corrosion and biological tests proved the good compatibility even for medical applications. 21 The biological tests show an accelerated settlement of cells and excellent proliferation. Furthermore, boron reveals no toxic effect within the low concentration used in this alloy.…”

Metal injection moulding of titanium and titanium alloys: Challenges and recent development

“…The most successful process may be a small addition of grain refining agents such as boron, LaB 6 and TiC to the feedstock [43,45,[81][82][83]. Post sintering heat treatments may also improve the ductility and strength of MIM components through their modification of microstructure.…”

“…In addition, post-processing may be needed to improve the density for specific applications. For instance, where fatigue resistance is important, a shot peening process has been shown to reduce the surface porosity which improved the fatigue strength by 100MPa [44,45]. Hot isostatic pressing (HIP) is a common process used to improve the density and mechanical properties of MIM and other powder metallurgy components.…”

“…Post sintering heat treatments may also improve the ductility and strength of MIM components through their modification of microstructure. .5B with a density of 97.7% [45] and d)…”

Development and Design of Binder Systems for Titanium Metal Injection Molding: An Overview

“…Contaminants, either in the original titanium powder, from the sintering atmosphere, or most likely from the binder, are usually a big concern for the component designers because these impurities deleteriously affect the mechanical properties of the final products. [9,10] In this sense, a comprehensive understanding of the binder system and the debinding processes helps us to provide a guideline for choosing a suitable powder feedstock and to validate the MIM approach. Research, development, and market status of MIM processes has been regularly reviewed, [8,[11][12][13] and they do not form the scope of this article.…”