Crystallisation and hydrogen absorption in amorphous Cu60Zr40and Cu50Zr50

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Abstract
The crystallisation processes in as-quenched and hydrogenated amorphous alloys of composition Cu100-xZrx (x=40 and 50) have been studied using differential thermal analysis and X-ray diffraction measurements. The as-quenched samples with x=40 and 50 yield crystallisation temperatures of 761 and 716K, respectively. X-ray diffraction measurements of fully crystallised samples show that crystallisation products are Cu10Zr7 from Cu60Zr40, and both Co10Zr7 and CuZr2 from Cu50Zr50. Differential thermal analysis scans of electrolytically hydrogenated samples show four features: (1) a small exothermic peak at 460K; (2) a large exothermic peak at approximately 550K; (3) a cluster of exothermic peaks beginning at 710-748K; (4) a large endothermic peak at approximately 1050K. X-ray diffraction measurements show that the features may be identified as (1) relaxation of the amorphous structure, (2) partial crystallisation into ZrH2 and Cu, (3) complete crystallisation of the remaining amorphous phase into ZrH2 and Cu and (4) breakdown of the hydride and formation of crystalline products as found in the non-hydrogenated alloys.