Metal Injection Molding (MIM) of Magnesium and Its Alloys

Martin Wolff,Michael Dahms,Regine Willumeit-Römer,Thomas Ebel,Johannes Schaper,Frank Feyerabend,Thomas Klassen,Marc Suckert

doi:10.3390/met6050118

Abstract

Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and complex in shape, the metal injection molding (MIM) technique seems to be well suited for the near net shape mass production of such parts. Furthermore, MIM of Mg-alloys is of high interest in further technical fields. This study focusses on the performance of MIM-processing of magnesium alloy powders. It includes Mg-specific development of powder blending, feedstock preparation, injection molding, solvent and thermal debinding and final sintering. Even though Mg is a highly oxygen-affine material forming a stable oxide layer on each particle surface, the material can be sintered to nearly dense parts, providing mechanical properties matching those of as cast material. An ultimate tensile strength of 142 MPa, yield strength of 67 MPa, elastic modulus of 40 GPa and 8% elongation at fracture could be achieved using novel organic polymer binders for the feedstock preparation. Thus, first implant demonstrator parts could be successfully produced by the MIM technique.

Highlights

Powder metallurgy (PM) of magnesium and its alloys offers three major advantages in comparison to conventional primary shaping techniques from the liquid state and metal forming techniques from the solid state: PM processing of Mg facilitates homogeneous distribution of elements.PM allows us to obtain a fine-grained microstructure
Difficulties occurring during metal forming, which are due to the hexagonal lattice structure of magnesium, can be avoided by using PM-techniques
The tensile tests of sintered metal injection molding (MIM) Mg-0.9Ca dogbone-shape test specimen were performed green length according to DIN EN ISO 6892-1:2009 B on a materials testing machine

Summary

Introduction

Powder metallurgy (PM) of magnesium and its alloys offers three major advantages in comparison to conventional primary shaping techniques from the liquid state and metal forming techniques from the solid state: PM processing of Mg facilitates homogeneous distribution of elements.PM allows us to obtain a fine-grained microstructure. Powder metallurgy (PM) of magnesium and its alloys offers three major advantages in comparison to conventional primary shaping techniques from the liquid state and metal forming techniques from the solid state: PM processing of Mg facilitates homogeneous distribution of elements. The low grain size of the magnesium alloy metal powder can be kept or even reduced to the sub-micrometer scale using PM metal forming techniques, e.g., extrusion or equal channel angular pressing (ECAP) [1,2,3]. These techniques are suitable for the production of bar stock and semi-finished products only.

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Results

Conclusion