Neutron in situ crystallization studies of Ti-based BMGs
Résumé
The phase evolution upon heating of Ti40Zr25Cu9Ni8Be18 BMG was investigated by in situ neutron diffraction studies and compared to Differential scanning calorimetry measurements performed at the same heating rate. When the experiment is performed at the constant speed of 2 K/min, the amorphous to crystallization process proceeds by two complicated crystallization reactions: firstly, the precipitation of a cubic Ti(Zr)Be-2 phase at 608K (a = 6.603 angstrom), this phase then disappears at 810 K, secondly, by the formation at 749K of two phases which have been determined by neutron diffraction to be a C14 hexagonal Laves phase and a big cube (Zr, Ti)(2)Ni phase. When the sample is heated at 2 K/min, then hold at T-g + 158 = 713K (before T-x2 = 749 K) the (Ti, Zr)Be-2 phase develops. After 60 min, the big cube phase starts to appear, an important amorphous bump being still present. These in situ diffraction experiments and the different phases formed are presented and discussed