Views
5 years ago

2 µm - eTheses Repository - University of Birmingham

2 µm - eTheses Repository - University of Birmingham

IM I 165 G B 2 10 2 10

IM I 165 G B 2 10 2 10 µm µm Figure 4.67 SEM micrograph of TOPC10IM in the reacted area and markers setting the location of the EDS spots IM, I, B and G. The analysis at position I showed that the needle-shaped phase in Figure 4.66 consisted mainly of Al and Ti with minor fractions of Mg and Si. Based on the relative mass contents in Table 4.7, the molar ratio between Ti and Al was calculated to be 1:4. This indicates that this phase consisted of a titanium aluminide with minor fractions of Si and Mg. As predicted by the thermodynamic calculations and shown in the work of Beyer (53) the phase is TiAl3 with traces of the main elements of the infiltration alloy Al, Mg and Si. Table 4.7 Results of the EDS spot analysis performed on the phases shown in Figure 4.67. O Mg Al mass-% Si Ti IM 0.0 5.3 93.5 0.0 1.1 I 0.0 3.3 68.1 2.8 25.8 B 34.9 9.4 12.3 0.0 43.5 G 43.6 0.4 52.1 0.8 3.2 The EDS analysis at spot B in Figure 4.67 showed that the brown phase in Figure 4.66 b) consisted of predominantly Ti and O with minor fractions of Al and Mg. The molar ratio of the main phases was 1Ti : 2.4 O indicating a mixture of the initial reinforcement TiO2 and a

minor fraction of suboxides with higher titanium contents, for example, TiO or Ti2O3. The Ti and Al concentrations in B may have been a result of the EDS spot size which was larger than the phase itself. Finally, the main elements in spot G were Al and O with traces of Mg and Si. The molar ratio of Al to O was 1 to 1.4 and therefore this phase was Al2O3 with traces of Mg and Si. The EDS analysis and the optical microscope results of TOPC10IM enabled interpretation of the microstructure of the TOPC10IS MMC after thermal analysis, Figure 4.63. Based on their colours and shapes the mid-grey, brown and the light grey phases in the initial infiltration alloy areas can be attributed to Al2O3, TiO2 in combination with titanium suboxides, and TiAl3, respectively. During the SDTA cycle, TOPC10IS was kept at ambient pressure and therefore reactions in the MMC resulted in open porosity as no metal melt was intruded in the pores. In contrast, during squeeze casting, the porosity resulting from volume changes due to reaction of the preform material with the infiltration alloy was filled with molten metal, indicated by the light metal alloy shown in the MMC areas in Figure 4.66 a). Similarly the cracks were filled with metal. Reactions between the metal and the ceramics led to changes in the microstructure of FATOIM, as shown in Figure 4.68, which should be compared with FATOIS infiltrated with alloy IS, Figure 4.57 b). A needle-shaped grey phase grew from the reinforcement into the alloy and EDS analysis confirmed it to be TiAl3. The concentration of magnesium in the alloy was reduced from 9.3 to 7.5 %. In contrast to TOPC10IM, Al2O3 and titanium-suboxides could not be detected as distinctive phases in the ceramic-rich region of the MMC, which may be a result of the initial sub-micron scale of the initial titanium particles. The Saffil-fibre reinforcement was not affected. 166

PDF File 2 - University of Alabama at Birmingham
no· l'2-'1t1 - Repository - Texas A&M University
eTheses Repository - University of Birmingham
chapter 1 - eTheses Repository - University of Birmingham
MODULE 2 - eTheses Repository - University of Birmingham
eA - eTheses Repository - University of Birmingham
eTheses Repository - University of Birmingham
eTheses Repository - University of Birmingham
Caroline Winstanley - eTheses Repository - University of Birmingham
epinician precepts - eTheses Repository - University of Birmingham
Witch Shoes - eTheses Repository - University of Birmingham
pains of sin - eTheses Repository - University of Birmingham
B - eTheses Repository - University of Birmingham
Cymbeline - eTheses Repository - University of Birmingham
here - eTheses Repository - University of Birmingham
View - eTheses Repository - University of Birmingham
J - eTheses Repository - University of Birmingham
B - eTheses Repository - University of Birmingham
1 - eTheses Repository - University of Birmingham
5% - eTheses Repository - University of Birmingham
Table of Contents - eTheses Repository - University of Birmingham
Anne Bevins 606082 - eTheses Repository - University of Birmingham
attending to others - eTheses Repository - University of Birmingham
ford madox brown - eTheses Repository - University of Birmingham
Intrinsic Naturalism - eTheses Repository - University of Birmingham
Words for wood - eTheses Repository - University of Birmingham
Diane Hiley - eTheses Repository - University of Birmingham
A poetics of dwelling - eTheses Repository - University of Birmingham
chapter 1 - eTheses Repository - University of Birmingham
THE GOD–MAN - eTheses Repository - University of Birmingham