Alloy phase diagram, strengthening

As an instance, the partial Ti-Si-B phase diagram is presented in Fig. 1. Silicon is not practically dissolved in TiB, and is fully concentrated in the metal matrix and in a ternary boro-silicide when it forms. This ternary boro-silicide phase of unknown structure (designated here as the T-phase) was found to be present as a very fine dispersoid around 200 nm in diameter in the three-phase eutectic (Ti) + T + TiB (Fig. 2). The ternary eutectic alloy hardness vv temperature plot shows a great potential for strengthening up to 600°C in comparison with the binary (Ti) + TiB (Fig. 3). 

In view of the ternary Ni-Al-Nb phase diagram (see Fig. 29) there are various possible ways to form two-phase or three-phase alloys on the basis of NiAl by alloying with Nb. For the strengthening of NiAl, second phases with not too low Al contents are preferred with respect to de sity and oxidation resistance. Al3Nb witl tetragonal DO22 structure, which has be discussed in Sec. 3.3.2, and the La> phase NbNiAl with a hexagonal C... 

All Ni and Fe—Ni-based superalloys are alloyed with Al. This leads to a two-phase matrix consisting of the y-(Ni, Fe, Al) solid solution phase (fee, Al stmeture) and the intermetallic y -NisAl phase (LI2 stmeture), which has a superlattice structure relative to the fee stmeture of the y phase. The binary Al—Ni phase diagram in Fig. 3.1-128 shows clearly that the y phase is stable up to the melting range. The matrix phase y is solid solution strengthened by allo3dng additions of Cr, Mo, W, and... 

The NiAl intermetallic phases are of particular importance because of their use in strengthening Ni-based alloys, especially the superalloys used in high-temperature gas turbine blades (the Ni-Al phase diagram is shovm in Figure 12.12). Nickel aluminide (Ni-Al) is the simplest of these compounds. It is described by the Strukturbericht symbol B2, which tells us it has the CsCl structure, and the Pearson symbol cP2 tells us we have a cubic lattice with two atoms per unit cell. Therefore NiAl has Ni atoms on the comers of a cube and an A1 atom in the center (or vice versa). (Note this is not a bcc structure because the atom in the center is not the same as those on the comers.) The width of this phase in the phase diagram tells us that some solid solution is possible within the phase. 

Properties Solid solutions, dislocations V Mechanical properties Y Dislocations, slip sterns, strengthening mechanisms Y Phase equilibria, the iron-iron carbide phase diagram Mechanical properties of Fe-C alloys Y ... 

Pal] Palm, M., Concepts Derived fiom Phase Diagram Studies for the Strengthening of Fe-Al-Based Alloys , Intermetallics, 13(12), 1286-1295 (2005) (Phase Diagram, Review, Meehan. Prop., 81)... 

Euml] Eumann, M., Palm, M., Sauthoff, G., Iron-Rich Iron-Aluminium-Molybdenum Alloys with Strengthening Intermetallic mu Phase and R Phase Precipitates , Steel Res., 75(1), 62-73 (2004) (Experimental, Meehan. Prop., Phase Diagram,, , 48)... 

Risl] Risanti, D.D., Sauthoff, G., Strengthening of Iron Aluminide Alloys by Atomic Ordering and Laves Phase Precipitation for High-temperature Applications , Intermetallies, 13(12), 1313-1321 (2005) (Crys. Stmeture, Experimental, Meehan. Prop., Morphology, Phase Diagram, Phase Relations,, , 37)... 

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