Cold Gas Dynamic Spray (CGDS): formation of Ti-Al intermetallics

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Description:	Cold gas dynamic spray, CGDS (or kinetic spray) is a rapidly developing coating and manufacturing technology in which metal particles are deposited at velocities of over 700 m/s without significant melting. A new method for fabricating intermetallics is being developed, where the mixture of powders is compacted using CGDS technique, before it is transformed into a intermetallic by a controlled thermal treatment using a conventional furnace. This image is a SEM (back scattered electron) micrograph showing the set of Ti-Al intermetallic phases after a low-temperature annealing of a Ti/Al deposit at 650°C (below the melting point of Al) for 3 hours. The analysis shows that at this temperature all the phases (Ti3A, TiAl, r-TiAl2 and TiAl3) in the Ti-Al system are present, and that unreacted Ti and Al still remains. This shows as well that TiAl3 becoming dominant as the Al phase is eliminated from the deposit with time, which is a consequence of the fast diffusion of Al atoms into the Ti particles as described by classical powder metallurgy theory. Although some phases of the Ti-Al system are not clearly distinguished in the micrograph, they were identified using microprobe EDS analysis. The micrograph also shows the development of porosity in the TiAl3 phase and along the phase boundaries. The Ti/Al deposites are produced using a CGDS system, build in the Institute for Manufacturing, Department of Engineering, University of Cambridge.
Keywords:	cold spray • CGDS • cold gas spray • coating • deposition • sintering • intermetallics • aluminium • titanium • powder metallurgy • micrsocopy • porosity • SEM • image
Categories:	Materials > Metals & alloys > Aluminium & alloys Materials > Metals & alloys > Titanium & alloys Processes > Shaping > Spraying Processes > Shaping > Powder methods Processes > Surface treatments > Surface coatings Processes > Thermal treatments > Sintering Testing, analysis & experimentation > Microscopy
Created by:	Dr. Tatiana Novoselova, The University of Liverpool
License:	This resource is released under the Creative Commons Attribution license (3.0 Unported). You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). View the full legal code here.
Date created:	04 May 2005
Date added:	17 May 2011
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Resource ID:	3641
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