Views
5 years ago

2 µm - eTheses Repository - University of Birmingham

2 µm - eTheses Repository - University of Birmingham

4.8.11 Homogeneity

4.8.11 Homogeneity of MMC infiltrated with alloy IM The macrograph of the cross-section of the titania-reinforced MMC infiltrated with the Al-Si alloy (TOPC10IS) is compared to that infiltrated with an Al-Mg alloy (TOPC10IM) in Figure 4.65. The dark phase corresponds to the MMC and the light one to the unreinforced metal. (a) TOPC10IS (b) TOPC10IM 163 2 5 2 5 µm mm µm mm 2 5 2 5 µm mm µm mm Figure 4.65 Cross section of titania MMCs infiltrated with Al-Si (TOPC10IS) and Al-Mg alloy (TOPC10IM). The rectangle in TOPC10IM shows the zone of detailed microstructural investigations. When the preform was infiltrated with the Al-Si alloy (IS), the rectangular shape of the preform was reproduced in the MMC cross section, Figure 4.65 a). Under the same infiltration parameters, the Al-Mg alloy-infiltrated MMC exhibited large cracks filled with the matrix alloy. These cracks were located towards the bottom of the MMC along the x-axis, as shown in Figure 4.65 b). Further cracks occurred on top of the preform. A dark area was visible in the centre of the MMC where the characteristic macroscopic MMC colour changed to an optically different phase. A similar appearance was observed in the cross-section of the FATO hybrid preform infiltrated with the alloy IM. The microstructure in the dark area was investigated for both MMC types. For comparison, the microstructure of the MOPC20 preform infiltrated with the alloy IM was also investigated. Here the macroscopic structure appeared similar to that of the same preform type infiltrated with the alloy IS. Z X

4.8.12 Microstructure of MMCs with Al-Mg alloy IM matrix The microstructure in the central dark area of TOPC10IM of Figure 4.65 b) is presented in detail in Figure 4.66 a) and b). The microstructure changed significantly when compared with that of TOPC10IS shown in Figure 4.55 a). A minor fraction of the bright metal phase (IM) was left in the intergranular regions but it was predominantly replaced by a grey phase (I). The initial ceramic phase was replaced by a grey phase (G) and a brown phase (B). (a) (b) B Figure 4.66 Optical micrograph of the dark areas marked in Figure 4.65 b). a) Overview and b) detail with designation of the different coloured phases. The EDS analysis of the reacted MMC was performed in an area where residual matrix alloy IM was obvious. As shown in Figure 4.67, a spot analysis was carried out on the four optically different phases designated IM, I, G and B in Figure 4.66 b). The quantification of the spot analysis was limited to the main constituents, namely Mg, Al, Si, O and Ti, and the results are listed in Table 4.7. The phase designated IM was confirmed to be the infiltration alloy IM, although this had different composition to the initial alloy see Table 3.2. The Mg mass content was reduced from 9.3% to 5.3% and that of Ti increased from 0.04% to 1.1%. 164 I IM G

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
eA - eTheses Repository - University of Birmingham
MODULE 2 - 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
Cymbeline - eTheses Repository - University of Birmingham
B - eTheses Repository - University of Birmingham
here - eTheses Repository - University of Birmingham
View - eTheses Repository - University of Birmingham
J - eTheses Repository - University of Birmingham
1 - eTheses Repository - University of Birmingham
5% - eTheses Repository - University of Birmingham
B - 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
chapter 1 - eTheses Repository - University of Birmingham
THE GOD–MAN - eTheses Repository - University of Birmingham
Engineering texts - eTheses Repository - University of Birmingham
Life on Wings - eTheses Repository - University of Birmingham
ford madox brown - eTheses Repository - University of Birmingham
Rewriting history - eTheses Repository - University of Birmingham