Obtaining of a fine near-lamellar microstructure in TiAl alloys by Spark Plasma Sintering
Résumé
This work presents a study of the Spark Plasma Sintering of a boron and tungsten containing alloy (Ti49,92Al48W2B0,08, called IRIS) as a function of the sintering temperature. Microstructures of sintered alloys are analyzed by scanning and transmission electron microscopies. Investigations mainly focus on a fine near-lamellar microstructure. Attention is paid to both characteristic dimensions of this microstructure and orientation relationships between various phases. The fine near-lamellar microstructure is formed by lamellar grains surrounded by extended γ zones containing β0 precipitates. The size of lamellar grains ranges from 35 to 45 μm while the width of the borders remains between 5 and 10 μm. Effects of both boron addition and sintering temperature are studied. Orientation relationships between γ lamellae and γ grains in the borders, as well as between the γ matrix and the β0 precipitates are investigated. As a result of these investigations, a formation mechanism of this microstructure is proposed and discussed. The origin of the grain growth limitation during the SPS processing is particularly analyzed. © 2016 Elsevier Ltd. All rights reserved.
Mots clés
Boron
Electron microscopy
Grain growth
Intermetallics
Microstructure
Plasma diagnostics
Powder metallurgy
Scanning
Spark plasma sintering
Titanium alloys
Transmission electron microscopy
Transmissions
Tungsten
Alloy designs
Aluminides
Formation mechanism
Growth limitations
Lamellar microstructure
Orientation relationship
Scanning and transmission electron microscopy
Sintering temperatures
Sintering