Technical Paper: PIM International, Vol.2 No. 2 June 2008, pages 74-78, 2507 words

Authors: R. Zhang, J. Kruszewski and J. Lo

CANMET/MTL, Natural Resources Canada, 568 Booth St., Ottawa, Ontario K1A 0G1, Canada

Abstract

The Ti6Al4V alloy evaluated in this work was fabricated by the Powder Injection Moulding (PIM) process using an elemental mixed Ti powder. Samples with a sintered density of 99.5% of its theoretical and higher were achieved by optimising the sintering conditions. Sintering temperatures between 1250ºC and 1320ºC were used in this study. It was found that, of the sintering temperature range investigated, the sintering temperature had little effect on the sintered density whereas the sintering time played an important role. The mechanical properties of the sintered samples were comparable to the wrought alloy. The best mechanical properties obtained in this study were 122GPa in elastic modulus, 865MPa in tensile yield strength, and 955MPa in UTS with 12% of elongation. The relationships among sintering parameters, sintered density, microstructure and mechanical properties are being discussed.

Introduction

The application of titanium alloys has attracted a lot of attention for decades due to its excellent properties, such as low density, high strength and good resistance to corrosion and oxidation. However, the utilisations of these alloys have been limited to aerospace, medical and some high end automotive components due to their high raw material and manufacturing costs. These issues have to be addressed in order to expand the market for titanium utilisation and some review papers summarised the ways to reduce the cost of titanium products [1, 2]. PIM is a near net shape process which eliminates most of the secondary and machining processes for geometrically complex components and most importantly it is adaptable to high production rate. Therefore, PIM offers a low cost alternative for hard to machine materials such as titanium. The economics of this process can be found in a series of review papers written by R. M. German [3-5]. The future of titanium PIM will become brighter with the commercial availability of the low cost titanium powder [6-7] and the newly developed low reactive binder systems specifically for titanium powder [8-9].

In this study, Ti6Al4V alloy was fabricated by the PIM process using an elemental mixed Ti powder. Different sintering conditions were used to achieve a higher sintered density and optimised mechanical properties. Although there were some properties of Ti6Al4V alloy made by the PIM process being reported [10-13], an extensive study on the relationship between processing parameters and properties has not been addressed. This work was focused on the effects of sintering temperature and time on the sintered density, microstructure and mechanical properties of PIM Ti6Al4V alloy.

Further sections of this article include:

- Experimental procedure
- Raw materials
- Fabrication process
- Characterisation
- Results and discussion
- Effects of sintering temperature and time on sintered density
- Effect of sintering temperature and time on microstructure
- Effects of sintering temperature and time on mechanical properties
- Chemical analysis of sintered samples
- Fracture surface analysis
- Conclusion
- Acknowledgments
- References