Microstructure and properties of cold consolidated amorphous ribbons from (NiCu)ZrTiAlSi alloys

Amorphous ribbons of compositions (Ni56Cu2)Zr18Ti13Al6Si5 and (Ni36Cu23)Zr18Ti14Al5Si4 were consolidated by high pressure torsion (HPT) at room temperature. In the HPT experiments a 6 GPa pressure and two turns were applied. Samples in the form of discs, 6-7 times thicker than the ribbons and about 10 mm in diameter were achieved. The minimal deformation for the homogenous consolidation was estimated to be in the range of 400%. XRD showed that the microstructure was dependent on the composition. The sample with high Cu content remained amorphous while the sample with low Cu content revealed some crystallization. DSC experiments allowed a comparison of the glass transition temperature Tg and crystallization process of the amorphous ribbon and HPT sample which were different. The glass transition temperature Tg of the amorphous HPT sample of (Ni36Cu23)Zr18Ti14Al5Si4 composition decreased. For both alloys the nanohardness and the elastic modules showed decrease for cold consolidated samples in comparison to the ribbons.