Determining sintering mechanisms and rate of in situ homogenisation during master alloy sintering of Ti6Al4V

Abstract

A differential scanning calorimetry (DSC) method was developed capable of measuring the rate of in situ alloying during Al–V master alloy (MA) sintering of Ti6Al4V based on monitoring the characteristics of the β–α phase transformation during cooling from the sintering temperature. The beta transus temperature and transformation temperature range both decreased with increasing sintering time, while the enthalpy of transformation increased. Supporting microstructural analysis confirmed that this change in the β–α phase transformation behaviour was due to interdiffusion of Ti, Al and V between the MA particle and CP-Ti matrix and the progressive dissolution of the MA particles. The majority of in situ alloying and MA dissolution occurred within one hour, while 3 h of sintering was required to achieve a level of homogenisation similar to that measured for a wrought Ti6Al4V sample. The use of finer MA particles resulted in more rapid and complete homogenisation.

Keywords:

• Sintering
• Titanium alloys
• Differential scanning calorimetry
• Homogenisation
• Ti6Al4V
• Phase transformation
• Diffusion

Acknowledgements

The authors would like to thank the Natural Science and Engineering Research Council of Canada and its Automotive Partnerships Canada programme for their financial support of this research. They would also like to thank Wescast Industries Inc. and Kingston Process Metallurgy Inc. for their financial, in-kind and technical support. We acknowledge the efforts of Clark Murray and William Sparling for their contributions towards some of experimental work reported in this paper.