Structural stability of the Laves phase Cr2Ta in a two-phase Cr–Cr2Ta alloy

Polytypic transformations in Laves phases

“…This is illustrated for the case of the Cr 2 Ta Laves phase in a two-phase Cr-Cr 2 Ta alloy in Fig. 2a -d [20]. A bright field image of a Cr 2 Ta precipitate in an as-cast specimen is shown in Fig.…”

“…Following a 100 h anneal at 1673 K, a temperature well below the eutectoid temperature (, 1858 K), the composition of the C15 phase changes marginally to 68.1 at.% Cr [11]. This response is, however, not typical of two-phase alloys in the other systems (Cr -Cr 2 Hf [19], Cr -Cr 2 Ti and Ti -Cr 2 Ti [15] and Cr-Cr 2 Ta [20]), where the hexagonal C14 (or C36) is metastably retained in the ascast condition. A micrograph of a Cr 2 Hf particle in a cast and forged two-phase Cr -Cr 2 Hf alloy [19] is shown in Fig.…”

“…1c. This can be contrasted with the twinned C15 structure (twinning is of the type [11][12][13][14][15][16][17][18][19][20]. Annealing the material at 1273 K for 1000 h results in the Laves phase changing to the C36 structure as seen in the diffraction pattern in (c).…”

Structure and stability of Laves phases part II—structure type variations in binary and ternary systems

“…A representative example is the Cr-Ta system [73][74][75][76][77][78][79][80][81][82]. The phase diagram shown in Fig.…”

Effect of Ru additions on microstructure and mechanical properties of Cr–TaCr2 alloys

“…In the Nb-Cr system, for example, Nb and Cr both form eutectic structures with NbCr 2 , and therefore, such 'in situ composites' have intrinsic stability. Moreover, the precipitation and coarsening kinetics of the Laves phases in Cr-Nb, Cr-Hf, and Cr-Ta systems was found to be extremely sluggish, even at 1200 8C, indicating a slow diffusion process in these dual-phase alloys [16][17]. Ductility and toughness were found to increase with decreasing were achieved in a NbCr 2 -based alloy with a Nb matrix [18].…”