Cold-crucible directional solidification of refractory metal-silicide eutectics

Deformation Mechanisms in Niobium Silicide-Based Composites

“…It contained both metallic and M 3 Si intermetallic dendrites, a small amount of an MsSi 3 intermetallic (where M represents Nb, Ti and Hf), and an interdendritic eutectic of silicide and metal. In this regard, it is entirely analogous to hypereutectic binary Nb-Si and ternary Nb-Ti-Si composites reported previously (Chang et al, 1992). The M 3 Si dendrites possessed the distinctive faceted morphology that has been reported previously in the binary hypereutectic («1222JÜSJ Figure 3 Scanning electron micrographs of (a) the longitudinal section of DS Nb-27Ti-16Si, (b) the transverse section of Nb-27Ti-16Si, (c) the longitudinal section of the DS MASC (after Bewlay, Lewandowski et ed., 1997).…”

“…This process is shown schematically in Figure 1 (b). A broad range of Nb-based RMICs with melting points up to ~2300°C (Bewlay et al, 1994a(Bewlay et al, , 1995a(Bewlay et al, , 1997cChang et al, 1992) has been produced. The alloys were induction levitation melted in a segmented water-cooled copper crucible.…”

“…Samples up to ~ 15 mm diameter and > 100 mm long have been directionally solidified using the Czochralski approach. The process has been described in further detail elsewhere (Chang et al, 1992;Bewlay et al, 1994aBewlay et al, , 1994b. Typically, high purity elements (> 99.99%) have been used for preparation of these composites, because great attention to the interstitial level is required.…”

“…Figure 3(c) shows a typical scanning electron micrograph (backscatter electron (BSE) imaging) of a longitudinal section of a specific metal and silicide composite (MASC) microstructure for which a broad range of properties have been reported (Bewlay et al, 1997b). This composite was derived from the binary Nb-16Si composition (Chang et al, 1992;Bewlay et al, 1994aBewlay et al, , 1995b. It contained both metallic and M 3 Si intermetallic dendrites, a small amount of an MsSi 3 intermetallic (where M represents Nb, Ti and Hf), and an interdendritic eutectic of silicide and metal.…”

MoSi₂ and Other Silicides as High Temperature Structural Materials

“…Though conventional in nature, these processes as applied to high melting silicides present other problems. For example with a lack of suitable) ceramic container, the directional solidification must be carried out in a containerless manner, either using induction, electron or optical float zone [20,21]. Microstructures of Cr/Cr$Si eutectic presented in Figure 13 bring forth the fine scale and uniformity produced by cold crucible directional solidification [20].…”