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A newly developed porous Ti35Zr28Nb scaffold was manufactured via powder metallurgy (PM) using space-holder (NH4HCO3) sintering from pre-alloyed powder. The pore features, compression and anti-corrosion properties of the manufactured porous scaffolds were systematically studied. The results show that all the manufactured porous Ti35Zr28Nb scaffolds consisted of a single β phase. The porosity of the porous Ti35Zr28Nb scaffolds increased from 50% to 65% with in increasing the NH4HCO3 from 63% to 79% (volume ratio), and the average pore size (d50) was in the range of 230–430 μm. The yield strength in compression and the elastic modulus of the porous Ti35Zr28Nb scaffolds both decreased gradually with an increase in porosity, varying from 230.5 MPa to 79.7 MPa and 6.9 GPa to 1.8 GPa, respectively. The corrosion rate of the porous Ti35Zr28Nb scaffolds in the phosphate buffer saline (PBS) solution increased from 0.91 × 10−3 mm/yr to 4.18 × 10−3 mm/yr with an increase in porosity from 51.4% to 64.9%. In comparison with unalloyed Ti scaffolds with almost the same porosity, the porous Ti35Zr28Nb scaffolds showed a significantly higher compressive yield strength and a lower corrosion rate. These results suggest that porous Ti35Zr28Nb scaffolds fabricated by PM have substantial potential for hard-tissue engineering applications. Additionally, the relationship of porosity, mechanical and anti-corrosion properties of these Ti35Zr28Nb scaffolds has now been confirmed, and could be used in the process of material selection for their specific applications. Keywords: Corrosion resistance, Mechanical property, Porous Ti35Zr28Nb scaffold, Powder metallurgy, Pore characterization

At present, the binder’s properties for metal injection molding (MIM) are assessed by rheological measurements and thermal decomposition temperature of the backbone polymer. Although blend studies of common polymers are available in the literature, little attention has been paid to study specific interactions among the particular binder system components and the effects of such interaction on reactive powders-MIM feedstocks are largely missing. This chapter aims to give readers some basic knowledge about polymer blends, their thermodynamics, and the possible interactions among individual components of common binder systems. In the last section, interactions between a binder system and metallic powder are also explained. After going through this chapter, the readers should be able to identify the importance of such interactions and know-how these interactions can be used to improve the properties of a feedstock.

The control of impurities—mainly carbon, oxygen, hydrogen, and nitrogen—is a key aspect of metal injection molding (MIM). The two most critical impurity elements to consider for reactive powders are oxygen and carbon because titanium has a high affinity toward oxygen and all binders are essentially carbon-based chains. This chapter highlights the importance of impurity control and the impact of it on mechanical properties. It also discusses the processing steps that should be taken to keep it in check.

This chapter briefly introduces each step involved in metal injection molding. It also introduces the evolution of metal injection molding technologies, opportunities, applications, and some constraints.

The binder system is an integral part of the metal injection molding (MIM) process. This chapter presents a general classification of the binder systems used for reactive powders MIM and discusses the critical aspects in terms of feedstock chemistry and properties. The first section of the chapter focuses on the binders’ chemistry. The importance of the main constituent in binder systems is highlighted. Classification of the binder systems and their subsequent removal after the injection molding process are discussed in the next section. Feedstock chemistry and properties are discussed in the final section, with a focus on the critical aspects of feedstock technology such as effects of solids loading and shear sensitivity in detail.

This chapter provides information on some potential feedstocks used for metal injection molding of reactive metals. It also reports a few successful case studies of using either commercial or custom-made feedstocks.

This chapter provides perspectives of the future trends in reactive metallic powder injection molding.

In spite of its great potential, the polyethylene glycol (PEG) and polymethyl methacrylate (PMMA) binder system was found susceptible to void nucleation, as the rigid PMMA chains hinder PEG volumetric shrinkage upon cooling. We previously reported that this void formation could be minimized by either using a higher cooling rate or by incorporating a crystallization inhibitor in the binder system. In this paper, efforts have been made to increase the workability of this binder system for conventional metal injection molding (MIM) by adding the crystallization inhibitor, polyvinylpyrrolidone (PVP). Differential scanning calorimetry (DSC), rheological property measurements, solvent and thermal debinding behavior, and fracture surface analysis of the molded samples were performed. Incorporation of PVP into the PEG/PMMA binder system is successful in that high quality void-free MIM components have been produced while maintaining the clean nature of the PEG/PMMA binder system. Keywords: PEG/PMMA, Void nucleation, Metal injection molding, Polymer crystallization