article posted 2 Apr 2016
Dr Phillip Mallinson works for AWE as a Materials Scientist. After graduating from the University of Oxford with a degree in Chemistry he completed a PhD on microwave dielectric ceramics at the University of Liverpool.
Development of a glass-ceramic seal for Ti-6Al-4V
Martyn T. Staff, Faye H. McCarthy, Paul M. Yates, Mark J. Whiting, Julie A. Yeomans, Phillip M. Mallinson*
AWE, Aldermaston, Reading, RG7 4PR
University of Surrey, Guildford, Surrey, GU2 7XU
Titanium and titanium alloys, such as Ti-6Al-4V, have an outstanding combination of
strength-to- weight ratio and corrosion resistance. However, applications such as
electrical housing and feed- throughs are limited by the difficulty in producing
suitable glass-to-metal seals (in terms of strength, hermeticity and humidity resistance).
This primarily arises from the formation of deleterious titanium silicide phases when
conventional silicate based glasses are used.
Investigation into boroaluminate glasses has shown they are capable of overcoming
these issues, whilst forming the desired hermetic seal. In this work a range of borate
based glasses have been examined, by dilatometry, DTA/DSC, XRD and electron
microscopy, as candidate compositions for a sealing system comprising a Ti-6Al-4V
alloy housing and a single pin of an appropriate alloy.
The crystallisation behaviour
of a strontium boroaluminate glass, see Figure 1, was investigated in order to produce
an optimised sealing procedure. The quality of the seals was then evaluated in terms
of hermeticity, mechanical strength and microstructure, see Figure 2.