Solidification processing of high temperature intermetallic eutectic-based alloys

Solidification Process and Mechanical Behavior of the Nb/Nb₅Si₃ Two Phase Alloys in the Nb-Ti-Si System

“…6) Previous studies have demonstrated that the A2/D8 l twophase alloys in the Nb-Si binary system exhibit moderate toughness at ambient temperature and reasonable strength at elevated temperature. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] However the binary A2/D8 l twophase alloys with Nb-rich composition show insufficient oxidation resistance for practical use, 27) and therefore, the studies gradually evolve into multi-component systems by which balance is pursued between mechanical properties and environmental resistance. Much effort has been made to clarify the effect of alloying elements with the Nb-Si binary alloy system upon the mechanical properties and oxidation resistance.…”

Deformation Mechanisms in Niobium Silicide-Based Composites

“…binary Nb-Si alloys and the ternary Nb-Ti-Si composites (Bewlay et al, 1995b(Bewlay et al, , 1997b. The metallic and intermetallic dendrites of the MASC were aligned with the growth direction.…”

“…The Nb 5 Si 3 and Nb 3 Si have tI32 and tP32 crystal structures, respectively. Analogous ternary Nb-Ti-Si alloy composites have also been investigated Bewlay et al, 1994aBewlay et al, , 1995bBewlay et al, , 1997c; a typical microstructure of a DS ternary NbTi-Si alloy composite is also shown in Figure 3(a) and (b); it consists of interpenetrating dendrites of the (Nb) and Nb 3 Si in the composite, with dendrite cross-sections of the order of 5-50 um wide.…”

“…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.…”

“…There is also a eutectoid of the form Nb 3 Si -(Nb) + Nb 5 Si 3 (Massalski, 1991;Mendiratta and Dimiduk, 1991). (Nb)-Nb 3 Si and (Nb)-Nb 5 Si 3 composites have been prepared by arc-melting, as well as directional solidification, of binary Nb-Si alloys (Bewlay et al, 1995b) with compositions from 10 to 25 Si; all compositions are given in atom percent throughout this chapter. A typical composite from a DS Nb-14 Si alloy is shown in Figure 2.…”