If the B2 phase with a superlattice structure appears in the CuZr-based amorphous alloy, what does it mean? Compared with ordinary diffraction patterns, what effect does this superlattice structure have on the mechanical properties of amorphous alloys?
Dear Shuang,
An amorphous alloy is like a glass, without any crystalline estructure. The diffraction pattern should be constituted by circles or very broad and distributed peaks associated with themena averaged of the distances at nn and nnn.
However, this alloy eventually can become locally crystalline (for instance because of thermal treatments) and this new phase will have a specific crystalline lattice with particular lattice parameters. If the amount is enough you should observe the diffraction peaks corrsponding to this lattice.
In the previous case, the new lattice could be a "disordered lattice" (every atom can be placed in any position of the lattice, with no preferential bonds). Nevertheless, if there are some preferential bonds (with different bonding energy) your lattice could become "crystalline ordered" at next-neighbor, so B2, and in this case, the extintion rules for the X-ray diffraction must change the pattern of the diffraction peaks that you must observe.
Obviously the apparition of ordered crystalline phases (like precipitates) inside the amorphous matrix will have an important impact on the mechanical properties. You could expect several changes: probably a small increase in the Young modulus, as well as an increase on the yield point and in general a modification of the ductility of your amorphous alloy.
I hope that my answer could be useful for you.
Best regards,
Prof. J. San Juan
Dear Shuang,
You should also consider that the addition or induction of precipitation of particles such as those of the B2-CuZr phase in metal alloys that have an amorphous structure (metal glasses (MGs) such as CuZr-based amorphous) are used as procedures to improve the mechanical properties of MGs. The effect of B2-CuZr particles on the mechanical properties of MGs depends on the size of the crystals, the volume fraction, the shape of distribution (homogeneous or not), possible phase transformation, orientations of the crystalls, etc. Many of the effects of the particles can be altered by heat treatments.
Best regards, Carlos
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