In-situ X-ray radiography of primary Fe-rich intermetallic compound formation

Abstract

The formation of primary Fe-rich intermetallic compound crystals and the effect of TiB 2 and TiC inoculation during solidification of a hypereutectic Al-Fe alloy has been investigated. Both horizontal, near isothermal conditions and vertical, directional thermal gradient conditions were studied using laboratory and synchrotron X-ray radiography. TiB 2 and TiC inoculation enhanced formation of Fe-rich intermetallics under all experimental conditions. Near isothermal solidification resulted in the highest intermetallic number density and average formation rate, whilst increasing the thermal gradient reduced both. A model for intermetallic crystal formation is proposed to explain the effect of thermal gradient and cooling rate on the intermetallic number density and average formation rate.

Tomoscopy: Time‐Resolved Tomography for Dynamic Processes in Materials

“…[ 79–81 ] Recently published work, for example from Feng et al., who studied a solidifying Fe‐rich intermetallic compound with radioscopy at 4 K s −1 , is directed toward higher rates, but 3D information is still lacking. [ 82 ] Up to the present, such processes cannot be studied with time‐resolved X‐ray imaging in 3D due to the lack of temporal resolution. Salvo et al.…”

In situ mapping of chemical segregation using synchrotron x-ray imaging

“…Switching from primary -Al crystal formation to secondary phases, Feng et al investigated the formation of Al13Fe4, one of the most commonly formed Fe-rich intermetallic compounds (IMCs) in commercial Al alloys [28]. Figure 5(h) shows a radiograph of primary Al13Fe4 crystals forming as the first phase in an Al-3wt%Fe alloy at 0.5 Ks -1 .…”

“…(e)-(g) A radiograph sequence showing formation of equiaxed α-Al crystals in an Al-25Cu alloy inoculated with TiB2 particles at 0.3 Ks -1 , at times t = 16 s, 29s and 38 s respectively (t = 0 was set to the frame when the first crystal appeared in the field of view) [23]. (h) A radiograph of primary Al13Fe4 crystals in a solidifying Al-3Fe alloy at 0.5 Ks -1 [28]. (i) The solute profile with a best-fit to theory in [29], along the direction indicated by the red arrow in (h) [28].…”

“…(h) A radiograph of primary Al13Fe4 crystals in a solidifying Al-3Fe alloy at 0.5 Ks -1 [28]. (i) The solute profile with a best-fit to theory in [29], along the direction indicated by the red arrow in (h) [28].…”

X-ray Imaging of Alloy Solidification: Crystal Formation, Growth, Instability and Defects

“…Unlike the aforementioned works that largely focused on X-ray imaging techniques, the current work instead presents a comprehensive review of knowledge provided by in situ X-ray imaging, for better understanding of solidification theories. Thanks to the high spatial (sub-micron) and temporal (microseconds) resolution offered by third-generation synchrotron sources, significant progress has been made in the understanding, validation and development of theories and models for near-equilibrium solidification, including solute suppressed nucleation (SSN) of both primary solid-solution α-Al [9][10][11][12][13][14] and secondary ordered intermetallics [15,16], dendritic growth of α-Al [17][18][19][20][21][22] and faceted, twin plane re-entrant (TPRE) growth of Fe-rich intermetallics [23][24][25][26], crystal fragmentation [27][28][29][30][31][32], morphological transition [33][34][35][36][37][38][39][40] and defect formation [41][42][43][44][45][46][47]. The focus of solidification research on Al alloys derives from the relatively easy-to-achieve melting temperatures of around 660 °C, and excellent absorption contrast between Al and typical alloying elements such as Cu and Zn.…”