PSI - Issue 7

L. Lattanzi et al. / Procedia Structural Integrity 7 (2017) 505–512

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L. Lattanzi et al./ Structural Integrity Procedia 00 (2017) 000–000

b Fig. 2. Typical OM micrograph of a specimen: (a) near the surface; (b) at the center.

a

Table 2. Average values of grain size and secondary dendrite arm spacing at the center of the specimen cross-section. Microstructural parameter Average dimension [μm] Grain size 17 ± 8 SDAS 12 ± 2

The d /SDAS ratio results lower than 1.6: when this value is less than 2, the grain morphology is spherical or globular. This result confirms the previous observations of OM micrographs. The analysis of the polar figure reported in Fig. 3b shows that there is no evidence of a preferential orientation of the grain structure. In order to reveal and identify the intermetallic phases in the examined alloy, EDS spectra and elemental maps were performed and the results were presented in previous works (Fabrizi et al. 2013). Acicular Fe-rich compounds were identified as -Al 5 FeSi phase. The XRD spectrum in Fig. 4a confirmed the presence of more frequent intermetallic compounds such as -Al 2 Cu and blocky -Al(Fe,Mn,Cr)Si ( sludge ) phases. A SEM micrograph indicating the latter intermetallic compounds is depicted in Fig. 4b.

a b Fig. 3. (a) α -Al grain size dimension distribution; (b) EBSD orientation map obtained in the central cross-section of the specimen.