Synthesis of Transition Metal Aluminides from Elemental Powder Mixtures
Författare
Summary, in Swedish
Popular Abstract in English
Structural components such as those used in gas turbines for energy conversion applications, are subjected to high
loads at elevated temperatures. In order to ensure that the components survive under these conditions for a
sufficiently long time, it is imperative to select materials with good high temperature properties like strength and
corrosion resistance. Such materials are usually alloys with a microstructure consisting of several phases where one
or more phases have a strengthening effect. These phases are generally hard and are compounds formed from two or
more metals. Current trends show an increasing interest in the use of such intermetallic compounds. The vast
potential of intermetallic compounds like aluminides emerges from a combination of their attractive characteristics
such as high melting point, high-temperature strength and excellent oxidation resistance. Transition metal
aluminides fall into this category and the formation of these compounds from elemental powder mixtures is the
focus of this thesis. Thermal effects (release and absorption of heat) have been studied during the heating of powder
compacts containing aluminum and a transitional element (Ti, Fe, Nb and Ta), using a differential scanning
calorimeter (DSC). The reaction behavior in samples containing two transitional elements (Ni and Ti), have also
been studied. The effects of changes in sample composition, particle size and heating rate on the onset temperatures
were investigated and the products obtained during various stages of reaction were characterized using scanning
electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).
The results from the present study show that high melting transition metal aluminides can be produced using the
powder metallurgical route at relatively low temperatures. However, the synthesis of pure compounds requires
careful control over critical process parameters like particle sizes of the reactants, composition, temperature and
time. The knowledge obtained from studies on the evolution of phases in various powder mixtures is useful in
optimizing process parameters. Studies on Al-Ni-Ti compacts have revealed the formation of ternary phases during
reactive sintering, which have not been observed during conventional production.
Structural components such as those used in gas turbines for energy conversion applications, are subjected to high
loads at elevated temperatures. In order to ensure that the components survive under these conditions for a
sufficiently long time, it is imperative to select materials with good high temperature properties like strength and
corrosion resistance. Such materials are usually alloys with a microstructure consisting of several phases where one
or more phases have a strengthening effect. These phases are generally hard and are compounds formed from two or
more metals. Current trends show an increasing interest in the use of such intermetallic compounds. The vast
potential of intermetallic compounds like aluminides emerges from a combination of their attractive characteristics
such as high melting point, high-temperature strength and excellent oxidation resistance. Transition metal
aluminides fall into this category and the formation of these compounds from elemental powder mixtures is the
focus of this thesis. Thermal effects (release and absorption of heat) have been studied during the heating of powder
compacts containing aluminum and a transitional element (Ti, Fe, Nb and Ta), using a differential scanning
calorimeter (DSC). The reaction behavior in samples containing two transitional elements (Ni and Ti), have also
been studied. The effects of changes in sample composition, particle size and heating rate on the onset temperatures
were investigated and the products obtained during various stages of reaction were characterized using scanning
electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).
The results from the present study show that high melting transition metal aluminides can be produced using the
powder metallurgical route at relatively low temperatures. However, the synthesis of pure compounds requires
careful control over critical process parameters like particle sizes of the reactants, composition, temperature and
time. The knowledge obtained from studies on the evolution of phases in various powder mixtures is useful in
optimizing process parameters. Studies on Al-Ni-Ti compacts have revealed the formation of ternary phases during
reactive sintering, which have not been observed during conventional production.
Avdelning/ar
Publiceringsår
2015
Språk
Engelska
Fulltext
- Available as PDF - 39 MB
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Dokumenttyp
Doktorsavhandling
Förlag
Lund University (Media-Tryck)
Ämne
- Materials Engineering
Nyckelord
- Aluminides
- Intermetallics
- Powder Metallurgy
- Reactive Sintering
- Combustion Synthesis
- Thermal Analysis
- DSC
- Onset temperature
- Phase evolution
- SEM
- EDS
- XRD
Status
Published
Handledare
ISBN/ISSN/Övrigt
- ISBN: 978-91-7623-471-6
Försvarsdatum
30 oktober 2015
Försvarstid
13:00
Försvarsplats
Hall M:E at M-Building, LTH
Opponent
- Michael Gasik (Professor)