Amorphisation and Devitrification of Al -Transition Metal - Rare Earth Alloys

Amorphisation studies by rapid solidification of Al-based alloys containing a transition metal (TM) and a rare earth element (RE) are reported. Results on primary formation of Al nanocrystals are given and discussed in relation to possible nucleation mechanisms considering the effect of various RE elements (RE = La, Cc, Nd and Sm) in Al87Ni7RE6 alloys. Ti or Zr, immiscible with RE's, are added to the ternary alloys with the aim of revealing possible phase separation in the melt. Calculations of ternary Al-Ni-Ce metastable phase equilibria are helpful in understanding the transformation sequence. Composition profiles ahead of nanocrystals are computed using the DICTRA software which correctly predicts the occurrence of composition gradients. The surface fracture of mechanically tested samples are observed in TEM to check whether crystallisation is induced by deformation